000
FXUS66 KSEW 231659
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST MON NOV 23 2009
.SYNOPSIS...A WARM FRONT WILL BRING SOME RAIN TO WESTERN WASHINGTON
TODAY...MAINLY ALONG THE COAST AND IN THE NORTH. A WEAK COLD FRONT
WILL MOVE INLAND TONIGHT. WEAK HIGH PRESSURE WILL MOVE ACROSS THE
AREA TUESDAY. A WEAK WARM FRONT WILL MOVE THROUGH THE AREA TUESDAY
NIGHT...FOLLOWED BY ANOTHER WEAK COLD FRONT WEDNESDAY NIGHT AND
THANKSGIVING DAY....FOLLOWED BY AN UPPER TROUGH ON FRIDAY.
&&
.SHORT TERM...A WEAK WARM FRONT CLIPPING THE AREA THIS MORNING IS
BRINGING SPOTTY LIGHT RAIN TO MUCH OF THE AREA. THE PRECIP CAME IN
QUICKER AND FURTHER INLAND THAN WAS EXPECTED YESTERDAY. EVEN THE NEW
12Z NAM IS DRY THIS MORNING WITH THE EXCEPTION OF THE COAST. THE
GFS/ECMWF APPEAR TO HAVE A BETTER HANDLE ON THIS SHOWING SOME LIGHT
QPF THIS MORNING...INTENSIFYING DURING THE AFTERNOON AS THE MAIN
FRONT APPROACHES. QPF AMOUNTS APPEAR HIGHEST ON THE COAST/OLYMPIC
PENINSULA WHERE UP TO 1 INCH OF RAIN COULD FALL. MUCH LESS AMOUNTS
EXPECTED ELSEWHERE WITH SNOW LEVELS EXPECTED TO RISE THROUGH THE
DAY..RISING TO OVER 5000 FEET BY THIS EVENING. SNOW ACCUMULATIONS IN
THE PASSES SHOULD REMAIN BELOW ADVISORY CRITERIA...MAYBE UP TO A FEW
INCHES THIS EVENING BEFORE CHANGING TO RAIN.
THE FRONT DISSIPATES OVER WRN WA UNDER A BUILDING UPPER RIDGE
TONIGHT. THERE COULD BE SOME RESIDUAL LIGHT RAIN/DRIZZLE AND LOW
CLOUDS HANGING IN THROUGH TUESDAY MORNING. COULD END UP BEING A
RATHER MURKY DAY TUESDAY WITH SUBSIDENCE ALOFT AND RESIDUAL MOISTURE
TRAPPED IN THE LOWER LEVELS. QPF WILL BE LIGHT WITH HIGHER SNOW
LEVELS...THUS SNOW IN THE PASSES IS NOT EXPECTED.
HIGH PRESSURE BUILDS STRONGER OVER THE AREA TUESDAY NIGHT AND EARLY
WEDNESDAY...THEN SHIFTS EWD WEDNESDAY AFTERNOON AS THE NEXT FRONTAL
BAND APPROACHES. IT LOOKS LIKE PRECIP SHOULD HOLD OFF DURING THE DAY
THE HEIGHTS AND RISING THICKNESS VALUES INDICATING WARMER AIR ALOFT.
PRECIP ASSOCIATED THE THE FRONTAL BAND COULD START TO AFFECT THE
OLYMPIC PENINSULA AND COAST BY LATE IN THE DAY. MERCER
.LONG TERM...PREVIOUS DISCUSSION FOLLOWS...THE MODELS DISAGREE ON
HOW THE PATTERN WILL CHANGE IN THE LONGER RANGE. THE GFS SHOWS A
MUCH DRIER SOLUTION WHILE THE EUROPEAN MODEL IS WETTER. SO
CONFIDENCE IN THE EXTENDED FORECAST THANKSGIVING DAY THROUGH SUNDAY
IS RATHER LOW AND THE APPROACH IS A BROAD BRUSH. IN A VERY GENERAL
SENSE THEY AGREE THAT THANKSGIVING DAY THROUGH FRIDAY NIGHT WILL BE
WETTER AS THE FRONTAL SYSTEM SITTING OFFSHORE WEDNESDAY MOVES
THROUGH THE AREA. AND THEY AGREE THAT AN UPPER RIDGE WILL BUILD OVER
THE AREA OVER THE WEEKEND ...REDUCING THE THREAT OF WET WEATHER TO A
CHANCE. MCDONNAL
&&
.HYDROLOGY...THE SKOKOMISH RIVER REMAINS JUST ABOVE FLOOD STAGE
EARLY THIS MORNING. THE CURRENT RIVER MODEL FORECAST SHOWS IT
DROPPING BELOW FLOOD STAGE LATER TODAY...BUT THE ACTUAL RESULT WILL
DEPEND HEAVILY UPON THE OPERATION OF CUSHMAN DAM #2 ON THE NORTH
FORK OF THE RIVER. A PLANNED RELEASE OF WATER FROM THE DAM BEGAN
EARLY SATURDAY AND CONTINUES EARLY THIS MORNING.
TWO FRONTAL SYSTEMS WILL MOVE THROUGH THE AREA THROUGH WEDNESDAY
NIGHT...AND THE SNOW LEVEL WILL GRADUALLY CLIMB TO 7000-8000 FT.
THESE SYSTEMS WILL NOT BRING ENOUGH PRECIPITATION FOR FLOODING
CONCERNS ON ANY WESTERN WASHINGTON RIVERS...WITH THE POSSIBLE
EXCEPTION OF THE SKOKOMISH RIVER.
MODELS DIFFER ON THE THURSDAY SYSTEM. THE NAM IS LESS PROGRESSIVE
AND HANGS THE FRONTAL BOUNDARY UP OVER THE OLYMPIC PENINSULA.
RAINFALL RATES DO NOT LOOK INCREDIBLE BUT COULD BE ENOUGH FOR MINOR
FLOODING CONCERNS ON THE SKOKOMISH RIVER. THE OTHER MODELS ARE
WEAKER AND MUCH MORE PROGRESSIVE WITH THE FRONT AND WOULD NOT IMPLY
ANY FLOOD THREAT.
NO FLOODING IS EXPECTED ON THE GREEN RIVER AT ANY TIME DURING THE
FORECAST PERIOD.
&&
.AVIATION...AN UPPER LEVEL TROUGH CROSSING SOUTHERN BRITISH COLUMBIA
WILL PUSH A WEAKENING COLD FRONT TO THE WA COAST AROUND 00Z. AIR
MASS IS STABLE WITH GRADUALLY LOWERING CIGS IN RAIN EXPECTED AHEAD
OF THE WEAK FRONT. THE FRONT WILL MOVE INLAND AFTER 00Z THEN
EVENTUALLY DISSIPATE OVER SW WA 06Z-12Z.
LATEST OBS SHOW CIGS GENERALLY BKN-0VC040-060 OVER THE INTERIOR WITH
SOME SPOTTY MVFR STILL IN THE PROCESS OF DISSIPATING...WITH
LOCALIZED LIGHT RAIN INTERFERING WITH THIS. WILL SHOW A MINOR BREAK
IN THE RAIN AND KEEP CIGS UP THROUGH ABOUT 22Z BASED ON AN APPARENT
BREAK IN THE HIGHER CLOUDS ON IR IMAGERY. SHOULD SEE CIGS LOWER WITH
MORE WIDESPREAD RAIN TOWARD 00Z AS THE MAIN FRONT APPROACHES.
KSEA...WILL KEEP CIGS BKN-OVC040-060 FOR MOST OF THE DAY THEN
LOWERING TO BKN-OVC020-030 AFTER 03Z. NOT COMPLETELY CONFIDENT THAT
THE CIGS WILL GET DOWN TO BKN020 WITH THE FRONT SO WEAK...BUT THE
WINDS WILL WEAKEN TONIGHT AS WELL WHICH WOULD ALLOW CIGS TO LOWER A
BIT MORE. EXPECT SURFACE WINDS TO REMAIN S THROUGH THIS EVENING. KAM
&&
.MARINE...THE WEAKENING COLD FRONT WAS UP AROUND 49N/128.5W AROUND
16Z THIS MORNING. MODELS BRING IT TO THE N COAST LATE THIS
AFTERNOON...12Z NAM A LITTLE FASTER THAN THE 12Z GFS. MODEL
SOLUTIONS WEAKENING THIS FRONT AS IT MOVES INLAND SEEM ON TRACK
SINCE WATER VAPOR IMAGERY SHOWS WHAT APPEARS TO BE THE LAST
SHORTWAVE MOVING UP THE FRONT ALMOST TO QUEEN CHARLOTTE SOUND. MAIN
QUESTION AT THIS POINT IS HOW STRONG THE WINDS WILL BE. SHOULD SEE A
LITTLE STRENGTHENING IN THE WINDS THROUGH EARLY AFTERNOON...THEN
WEAKENING. WILL LEAVE THE GALES COAST/WEST ENTRANCE UP AND SCA
ELSEWHERE EXCEPT CENTRAL STRAIT. FORECAST ADVERTISES SCA W WINDS IN
THE STRAIT BEHIND THE FRONT TONIGHT...BUT NEITHER THE GFS OR NAM
SUPPORT THAT. WILL HOLD OFF ON THE ADVISORIES AND SEE WHAT THE 12Z
WRF-GFS SHOWS. WINDS SHOULD BE BELOW ADVISORY LEVELS
TUESDAY...EXCEPT FOR THE COAST. KAM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
PZ...GALE WARNING COAST AND WEST ENTRANCE.
SMALL CRAFT ADVISORY ALL OTHER WATERS EXCEPT THE CENTRAL
STRAIT.
SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS AT GRAYS HARBOR
ENTRANCE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 231131
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST MON NOV 23 2009
.SYNOPSIS...A WARM FRONT WILL BRING SOME RAIN TO WESTERN WASHINGTON
TODAY...MAINLY ALONG THE COAST AND IN THE NORTH. A WEAK COLD FRONT
WILL MOVE INLAND TONIGHT. WEAK HIGH PRESSURE WILL MOVE ACROSS THE
AREA TUESDAY. A WEAK WARM FRONT WILL MOVE THROUGH THE AREA TUESDAY
NIGHT...FOLLOWED BY ANOTHER WEAK COLD FRONT WEDNESDAY NIGHT AND
THANKSGIVING DAY....FOLLOWED BY AN UPPER TROUGH ON FRIDAY.
&&
.SHORT TERM...THE VIGOROUS SYSTEM THAT WAS MOVING INTO THE PACIFIC
NORTHWEST 24 HOURS AGO IS NOW LONG GONE...MAKING ITS WAY EAST OF THE
NORTHERN ROCKIES. AN UPPER LEVEL RIDGE HAS MOVED OVER THE PACIFIC
NORTHWEST OVERNIGHT -- THE BEGINNING OF A TREND TOWARD A HIGH
AMPLITUDE...LESS PROGRESSIVE...AND MUCH LESS EVENTFUL WEATHER
PATTERN THAT WILL CONTINUE THROUGH THE NEXT WEEK. SKIES ACROSS
WESTERN WASHINGTON ARE GENERALLY CLOUDY THIS MORNING WITH VERY
SPOTTY LIGHT PRECIPITATION...AS THE WARM FRONT OF A SYSTEM
IMMEDIATELY UPSTREAM OF THE RIDGE IS MOVING INTO THE FORECAST AREA.
TEMPERATURES ARE IN THE LOWER TO MID 40S.
THE UPPER RIDGE WILL PROGRESS EASTWARD TODAY ACROSS THE CASCADES AND
ALMOST TO THE EASTERN BORDER OF THE STATE. THIS WILL ALLOW THE
FRONTAL SYSTEM JUST OFFSHORE TO MOVE SLOWLY INLAND TODAY. IT WILL
BRING FAIRLY SIGNIFICANT PRECIPITATION AMOUNTS -- IN THE .50 TO 1.25
INCH RANGE -- TO THE COAST AND OLYMPIC PENINSULA...WITH SOMEWHAT
LESS OVER THE NORTH CASCADES. BUT THE FRONT WILL WEAKEN AS IT MOVES
THROUGH THE AREA TONIGHT...AND PRECIPITATION TOTALS FOR THE INTERIOR
LOWLANDS WILL MOSTLY BE LESS THAN 0.25 INCH. THE SNOW LEVEL...WHICH
IS STARTING OUT AROUND 2500 FT...WILL CLIMB TO AROUND 6000 FT
TONIGHT.
AS THE FRONT FALLS APART AND MOVES EAST OF THE CASCADES TUESDAY...
ANOTHER STRONGER UPPER RIDGE WILL MOVE OVER THE PACIFIC NORTHWEST.
THE RIDGE WILL SEND 500 MB HEIGHTS TO AROUND 5700 METERS. THE WARM
FRONT OF ANOTHER FRONTAL SYSTEM JUST UPSTREAM OF THIS RIDGE WILL
KEEP A CHANCE OF LIGHT RAIN IN THE FORECAST TUESDAY.
BY TUESDAY NIGHT THE UPPER RIDGE AXIS WILL BE EAST OF THE CASCADES
AND IT WILL MOVE SLOWLY EASTWARD TO THE ROCKIES ON WEDNESDAY NIGHT.
MODELS SHOW THE FRONTAL BAND TRANSLATING VERY SLOWLY EASTWARD AS IT
STRETCHES SOUTH-SOUTHWEST FROM VANCOUVER ISLAND. IT WILL KEEP A
CHANCE OF RAIN IN THE FORECAST FOR WESTERN WASHINGTON...BUT
PRECIPITATION WILL BE GENERALLY VERY LIGHT WHERE WE GET ANY...AND
THE MAIN THREAT OF PRECIPITATION WILL BE ALONG THE COAST AND OVER
THE OLYMPIC PENINSULA. THE SNOW LEVEL WILL BE 7000-8000 FT. MCDONNAL
.LONG TERM...THE MODELS DISAGREE ON HOW THE PATTERN WILL CHANGE IN
THE LONGER RANGE. THE GFS SHOWS A MUCH DRIER SOLUTION WHILE THE
EUROPEAN MODEL IS WETTER. SO CONFIDENCE IN THE EXTENDED FORECAST
THANKSGIVING DAY THROUGH SUNDAY IS RATHER LOW AND THE APPROACH IS A
BROAD BRUSH. IN A VERY GENERAL SENSE THEY AGREE THAT THANKSGIVING
DAY THROUGH FRIDAY NIGHT WILL BE WETTER AS THE FRONTAL SYSTEM
SITTING OFFSHORE WEDNESDAY MOVES THROUGH THE AREA. AND THEY AGREE
THAT AN UPPER RIDGE WILL BUILD OVER THE AREA OVER THE WEEKEND
...REDUCING THE THREAT OF WET WEATHER TO A CHANCE. MCDONNAL
&&
.HYDROLOGY...THE SKOKOMISH RIVER REMAINS JUST ABOVE FLOOD STAGE
EARLY THIS MORNING. THE CURRENT RIVER MODEL FORECAST SHOWS IT
DROPPING BELOW FLOOD STAGE LATER TODAY...BUT THE ACTUAL RESULT WILL
DEPEND HEAVILY UPON THE OPERATION OF CUSHMAN DAM #2 ON THE NORTH
FORK OF THE RIVER. A PLANNED RELEASE OF WATER FROM THE DAM BEGAN
EARLY SATURDAY AND CONTINUES EARLY THIS MORNING.
TWO FRONTAL SYSTEMS WILL MOVE THROUGH THE AREA THROUGH WEDNESDAY
NIGHT...AND THE SNOW LEVEL WILL GRADUALLY CLIMB TO 7000-8000 FT.
THESE SYSTEMS WILL NOT BRING ENOUGH PRECIPITATION FOR FLOODING
CONCERNS ON ANY WESTERN WASHINGTON RIVERS...WITH THE POSSIBLE
EXCEPTION OF THE SKOKOMISH RIVER.
THE FORECAST FOR THANKSGIVING AND BEYOND IS LESS CERTAIN...BUT AT
THIS TIME THERE DOES NOT APPEAR TO BE ANY THREAT OF FLOOD-PRODUCING
RAINS.
NO FLOODING IS EXPECTED ON THE GREEN RIVER AT ANY TIME DURING THE
FORECAST PERIOD.
&&
.AVIATION...THE TAIL END OF AN UPPER TROUGH WILL BRUSH BY THIS
AFTERNOON...PUSHING A WEAKENING COLD FRONT ACROSS WRN WA. FOG IS
BECOMING INCREASINGLY UNLIKELY THIS MORNING GIVEN THE THICKNESS OF
MID-LEVEL CLOUDS AND ENOUGH WIND TO MIX THE BOUNDARY LAYER. AN
OFFSHORE COMPONENT TO THE LOW-LEVEL FLOW IN ADVANCE OF THE FRONT
WILL LIMIT CLOUDS BELOW 040...EXCEPT NEAR HOOD CANAL. THE FRONT
SHOULD CROSS WRN WA FROM 00Z-06Z THIS EVENING...ACCOMPANIED BY RAIN
AND FOLLOWED BY INCREASING LOW-LEVEL MOISTURE OVERNIGHT TONIGHT.
KSEA...CIGS SHOULD IMPROVE THIS MORNING AS AN OFFSHORE LOW-LEVEL
FLOW COMPONENT STRENGTHENS IN ADVANCE OF THE APPROACHING FRONT AND
INHIBITS LOWER CLOUDS. A COLD FRONT WILL PASS KSEA BTWN 00Z-03Z ON
MON EVENING. WINDS ALOFT SHOULD PEAK AROUND THE TIME OF FROPA...WITH
SOUTHWEST 850 MB WINDS NEAR 40 KNOTS ARND 00Z. LOW-LEVEL MOISTURE
WILL INCREASE BEHIND THE FRONT WITH CIGS DETERIORATING TO IFR
TONIGHT AND CONTINUING ON TUE MORNING. HANER
&&
.MARINE...SOUTHERLY FLOW WILL INCREASE TODAY IN ADVANCE OF AN
APPROACHING FRONT. THE WIND AT BUOY 46036 GUSTED TO GALE FORCE IN
ADVANCE OF THE FRONT...SO AM THINKING LOW-END GALES SHOULD AFFECT
THE COASTAL WATERS TODAY. THE FRONT WILL BE WEAKENING QUICKLY AS IT
MOVES INLAND LATE THIS AFTN AND EVNG. AS A RESULT...NOT EXPECTING
THE GALES ALONG THE COAST TO TRANSLATE TO THE NORTH INTERIOR. SMALL
CRAFT WINDS OVER THE INLAND WATERS ARE THE MOST LIKELY OUTCOME AT
THIS POINT...BUT WILL NEED TO BE WATCHED. HIGH PRES WILL BUILD OVER
THE WATERS TONIGHT AND TUE WITH LGT TO MDT OFFSHORE FLOW DVLPG.
HANER
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
PZ...GALE WARNING COAST AND WEST ENTRANCE.
SMALL CRAFT ADVISORY ALL OTHER WATERS EXCEPT THE CENTRAL
STRAIT.
SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS AT GRAYS HARBOR
ENTRANCE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 230520
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
920 PM PST SUN NOV 22 2009
.SYNOPSIS...A WARM FRONT WILL BRUSH THE NORTHWEST PORTION OF THE
STATE LATE TONIGHT AND A COLD FRONT WILL MOVE THROUGH THE AREA MON
EVENING. WEAK HIGH PRESSURE WILL MOVE ACROSS THE AREA ON TUESDAY. A
ANOTHER WEAK WARM FRONT WILL MOVE THROUGH THE AREA TUESDAY NIGHT AND
WILL BE FOLLOWED BY ANOTHER WEAK COLD FRONT WEDNESDAY NIGHT OR
THURSDAY. ANOTHER WEAK COLD FRONT IS POSSIBLE FRIDAY NIGHT OR
SATURDAY.
&&
.SHORT TERM...IT APPEARS THAT WE SHOULD BE HEADING INTO A MORE
BENIGN WEATHER PATTERN FOR THE UPCOMING WEEK. WHILE IT WILL BE
MAINLY CLOUDY WITH OCCASIONAL BANDS OF LIGHT RAIN AS WEAK FRONTAL
SYSTEMS MOVE THROUGH THE AREA...WINDS...RAIN RATES...AND MOUNTAIN
SNOWFALL RATES SHOULD NOT BE A MAJOR ISSUE AS WEAK LONG WAVE RIDGING
FORMS OVER THE WESTERN U.S. AND FRONTS HAVE A TENDENCY TO WEAKEN AS
THEY MOVE ACROSS THE AREA.
TONIGHT ONSHORE PRESSURE GRADIENTS ARE SLOWLY RELAXING AS THE LOW
PRESSURE SYSTEM THAT MOVED THROUGH THE AREA EARLIER PULLS AWAY INTO
MONTANA. RADAR AND OBSERVATIONS SHOW PRECIPITATION RATES IN THE
CASCADES WITH SHOWERS AND A WEAK CONVERGENCE ZONE FROM CENTRAL
SNOHOMISH COUNTY INTO SOUTHERN WHATCOM COUNTY DECREASING RAPIDLY
THIS EVENING. WILL ALLOW THE WINTER STORM WARNING IN THE CASCADES
EXPIRE...AND WILL UPDATE THE ZONES TO REMOVE THE HEADLINES. ON THE
COAST THE SEAS HAVE FALLEN BELOW 20 FEET...SO WILL ALSO ALLOW THE
HIGH SURF ADVISORY EXPIRE AND UPDATE THE COASTAL ZONES TO REMOVE
THOSE HEADLINES.
A WEAK WARM FRONT NOW SITTING IN THE OFFSHORE WATERS WILL MOVE NE
THROUGH THE COASTAL WATERS LATER TONIGHT AND WILL CLIP THE OLYMPIC
PENINSULA EARLY MONDAY.
A COLD FRONT NOW SEEN JUST OUTSIDE OF 135W AT 50N IS MAKING STEADY
EASTWARD PROGRESS. ITS PRECIPITATION SHIELD SHOULD MOVE ONSHORE
DURING THE AFTERNOON HOURS MONDAY AND REACH THE INTERIOR MID TO LATE
AFTERNOON. LOW END GALE FORCE WINDS ARE LIKELY IN THE COASTAL
WATERS...BUT OTHER AREAS SHOULD SEE ONLY WINDS TYPICAL OF A WEAK TO
MODERATE FRONTAL SYSTEM MON NIGHT.
WARMER AIR ALOFT AND LIGHTER FLOW WILL COMBINE WITH LONG NIGHTS AND
LIGHTER FLOW TO GIVE MORE ABUNDANT STRATUS AND FOG TUESDAY. WILL
LEAVE THIS CHANGE TO THE NEXT SHIFT.
TEMPERATURES WILL BE GENERALLY MILD FOR THE LATTER PART OF NOVEMBER
FOR THE NEXT SEVERAL DAYS. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...I HAVE KEPT THE
GRIDS/FCSTS CLOSE TO CLIMO AND DO NOT SEE ANY WEATHER SYSTEMS THRU
SATURDAY THAT LOOK IMPRESSIVE OR NOTEWORTHY. THE FREEZING LEVEL
SHOULD TREND DOWN THRU THE WEEK AFTER PEAKING ARND 6500FT EARLY IN
THE WEEK. AFTER THE WEAK FRONT ON THANKSGIVING THERE IS ANOTHER
FRONT POSSIBLE LATE FRI...A WEAK TROF AT 500MB BUT THE GFS HARDLY
HAS A SURFACE REFLECTION. THE ECMWF IS STRONGER WITH COLD FRONT BY
12Z FRI...IT SHOWS A SFC LOW DEEPENING A BIT AS IT MOVES EAST ALONG
40N THURSDAY AND AS THAT SHIFTS INLAND BY FRIDAY MORNING SOMEWHERE
EAST OF THE CASCADES THERE IS FAIRLY STRONG ONSHORE FLOW INTO WRN
WA. THEN...IF THE GLOBAL MODELS ARE RIGHT HIGH PRES BUILDS OVER THE
PACNW FOR NEXT WEEKEND. 19
&&
.HYDROLOGY...THE ONLY CURRENT RIVER FLOOD PROBLEM IS THE SKOKOMISH
RIVER. IT IS JUST ABOVE FLOOD STAGE THIS EVENING AND WILL LIKELY
REMAIN ABOVE FLOOD STAGE INTO MONDAY AFTERNOON AS WATER IS RELEASED
FROM CUSHMAN DAM #2. THE SYSTEM WHICH WILL MOVE THROUGH WESTERN
WASHINGTON MONDAY AFTERNOON AND EVENING IS NOT A FLOOD-PRODUCING
RAIN SYSTEM BUT IT IS A WARM FRONT...SO RIVERS WILL PROBABLY STOP
RECEDING AND OLYMPIC RIVERS MIGHT TREND UP A BIT FOR A DAY. THE
FRONTAL SYSTEM WEDNESDAY NIGHT OR THURSDAY AND THE COLD FRONT LATE
IN THE WEEK LOOK RATHER WEAK AND AS IF THEY ARE MOVING INTO A MEAN
RIDGE POSITION. THE SNOW LEVEL WILL PROBABLY TREND DOWN THRU THE
WEEK AFTER PEAKING WED. THE BAROCLINIC ZONE THAT GETS HUNG UP ON
VANCOUVER ISLAND WED IS WORTH WATCHING BUT AT THIS TIME WE DO NOT
SEE A RISK FOR RIVER FLOODING. FLOODING IS NOT EXPECTED ON THE GREEN
RIVER OVER THE NEXT WEEK. ALBRECHT/19
&&
.AVIATION...A BRIEF LULL BETWEEN WEATHER SYSTEMS IS COMING UP
OVERNIGHT. THE PUGET SOUND CONVERGENCE ZONE ON THE BACK END OF THE
OUTGOING WEATHER SYSTEM IS DISSIPATING AS MORE GENERAL SOUTHERLY
FLOW STARTS TO TAKE OVER IN ADVANCE OF THE NEXT FRONT TO ARRIVE LATE
MON. BRIEF CLEARING OF SKIES OVERNIGHT COULD EASILY ALLOW LOCALIZED
FOG IN SHELTERED VALLEYS...BUT INCREASED SOUTHERLY WINDS ON MON
MORNING SHOULD MIX OUT ANY FOG. ON MON MORNING...AN OFFSHORE
COMPONENT TO THE LOW-LEVEL FLOW WILL LIMIT CLOUDS BELOW 040...EXCEPT
NEAR HOOD CANAL. THE FRONT SHOULD CROSS WRN WA FROM 00Z-06Z ON MON
EVENING...BUT THE FRONT WILL BE WEAKENING AND DISSIPATING AS IT
PASSES BY.
KSEA...THE RECENT TREND OF IMPROVING CIGS WILL CONTINUE OVERNIGHT
AND MON MORNING AS A TURN TO AN OFFSHORE LOW-LEVEL FLOW COMPONENT
INHIBITS LOW CLOUDS. A COLD FRONT WILL PASS KSEA BTWN 21Z-24Z ON
MON. WINDS ALOFT SHOULD PEAK AROUND THE TIME OF FROPA...WITH
SOUTHWEST 850 MB WINDS NEAR 40 KNOTS ARND 24Z. LOW-LEVEL MOISTURE
WILL INCREASE BEHIND THE FRONT WITH CIGS DETERIORATING TO IFR ON MON
NIGHT. HANER
&&
.MARINE...ONSHORE FLOW IS CURRENTLY WEAKENING AND WILL TURN TO
INCREASING SOUTHERLY FLOW OVERNIGHT AND MON MORNING IN ADVANCE OF
THE NEXT FRONT. THE FRONT IS NOT FAR WEST OF BUOY 46036...WHICH HAS
RECENTLY HAD GALE FORCE GUSTS. EXPECTING THE FRONT TO SUPPORT
LOW-END GALE FORCE SOUTHERLIES ALONG THE COAST...BUT THE FRONT WILL
BE WEAKENING QUICKLY AS IT MOVES INLAND ON MON AFTN AND EVNG. AS A
RESULT...NOT EXPECTING GALES ALONG THE COAST TO TRANSLATE TO THE
NORTH INTERIOR. SMALL CRAFT WINDS OVER THE INLAND WATERS ARE THE
MOST LIKELY OUTCOME AT THIS POINT. HIGH PRES WILL BUILD OVER THE
WATERS ON MON NIGHT AND TUE WITH LIGHT OFFSHORE FLOW DEVELOPING.
HANER
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
PZ...GALE WARNING COAST AND WEST ENTRANCE.
SMALL CRAFT ADVISORY ALL OTHER WATERS.
SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS AT GRAYS HARBOR
ENTRANCE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 222325
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
325 PM PST SUN NOV 22 2009
.SYNOPSIS...A LOW PRESSURE SYSTEM WILL CONTINUE TO MOVE INLAND
OVERNIGHT. WESTERLY GALES OVER THE COASTAL WATERS AND IN THE STRAIT
OF JUAN DE FUCA WILL DECREASE BY MIDNIGHT. SNOW SHOWERS WILL BE
HEAVY AT TIMES THROUGH THE EVENING IN THE MOUNTAINS. A WARM FRONT
WILL MOVE THROUGH THE AREA MONDAY EVENING...FOLLOWED BY ANOTHER WARM
FRONTAL SYSTEM AROUND WEDNESDAY NIGHT. A COLD FRONT IS POSSIBLE BY
FRIDAY.
&&
.SHORT TERM...SEA TAC AND TACOMA NARROWS AND HOQUIAM GUSTING TO ARND
30 MPH AT 3PM BUT I HAVE LET THE WIND ADVISORY EXPIRE NOW AS WE WONT
LIKELY MUCH MORE THAN THAT INTO THE EVENING AS GRADIENTS COME DOWN.
FINALLY BREEZY HERE AT THE OFFICE ON LAKE WASHINGTON...OLM-BLI
GRADIENT PEAKED AT +4.5MB EARLY IN THE AFTERNOON BUT THE WINDS IN
THE SOUTH SOUND JUST WOULD NOT SHIFT INTO NORTH SEATTLE AND
EVERETT...BUT BREEZY FOR A FEW HOURS LATE THIS AFTERNOON. SCATTERED
SHOWERS DECREASING OVERNIGHT...PLENTY OF SNOW SHOWERS IN THE
CASCADES THIS EVENING. AT 3 PM SHOWERS WERE MNLY PERSISTING IN
SKAGIT COUNTY AND THE CASCADES. THERE IS A CHANCE THAT THE PSCZ WILL
DEVELOP IN A MORE CLASSIC FASHION A BIT FURTHER SOUTH THIS
EVENING...BUT I HAVE POPS THAT MNLY JUST SHOW THE ACTIVITY PUSHED
INTO THE CASCADES. THE WINTER STORM WARNING FOR THE CASCADES WILL
END AT 9 PM AND MOST OF THE HEAVY SNOW SHOWERS OUGHT TO BE WINDING
DOWN BY THEN. WARM ADVECTION WILL BEGIN MONDAY AS THE NEXT FRONT
ARRIVES...THIS ONE WILL NOT BE PARTICULARLY STRONG...A TYPICAL WARM
OCCLUSION WITH DECENT SSE WINDS AHEAD OF THE FRONT BUT GRADIENTS
BECOMING RATHER LIGHT MONDAY NIGHT AND EARLY TUE AS THE FRONT
DISSIPATES OVER THE AREA. THEN ANOTHER ROUND OF WARM ADVECTION WILL
INCREASE THE CHANCE OF RAIN TUE NITE THRU WED...ALTHOUGH I HAVE THE
HIGHEST POPS ONLY OVR NW WA AND NORTH CASCADES WITH CHANCE POPS
SEATTLE SOUTH BY WED AS THE FRONT HANGS UP OVER MNLY VANCOUVER
ISLAND...THEN SAGS THRU WRN WA WED NITE OR THU. THE SYSTEMS IN THE
WEEK AHEAD ARE NOT ESPECIALLY STRONG AND WITH THE 500MB HEIGHT ONLY
FALLING 100M FROM LATE TUE THRU MIDWEEK IT SEEMS LIKELY TO BE A
CLOUDY DRIPPY WEEK WITH LITTLE IN THE WAY OF EVENTFUL WEATHER. 19
.LONG TERM...I HAVE KEPT THE GRIDS/FCSTS CLOSE TO CLIMO AND DO NOT
SEE ANY WEATHER SYSTEMS THRU SATURDAY THAT LOOK IMPRESSIVE OR
NOTEWORTHY. THE FREEZING LEVEL SHOULD TREND DOWN THRU THE WEEK AFTER
PEAKING ARND 6500FT EARLY IN THE WEEK. AFTER THE WEAK FRONT ON
THANKSGIVING THERE IS ANOTHER FRONT POSSIBLE LATE FRI...A WEAK TROF
AT 500MB BUT THE GFS HARDLY HAS A SURFACE REFLECTION. THE ECMWF IS
STRONGER WITH COLD FRONT BY 12Z FRI...IT SHOWS A SFC LOW DEEPENING A
BIT AS IT MOVES EAST ALONG 40N THURSDAY AND AS THAT SHIFTS INLAND BY
FRIDAY MORNING SOMEWHERE EAST OF THE CASCADES THERE IS FAIRLY STRONG
ONSHORE FLOW INTO WRN WA. THEN...IF THE GLOBAL MODELS ARE RIGHT HIGH
PRES BUILDS OVER THE PACNW FOR NEXT WEEKEND. 19
&&
.HYDROLOGY...THE ONLY CURRENT RIVER FLOOD PROBLEM IS THE SKOKOMISH
RIVER. IT IS JUST ABOVE FLOOD STAGE THIS AFTERNOON AND WILL LIKELY
REMAIN ABOVE FLOOD STAGE INTO MONDAY MORNING AS WATER IS RELEASED
FROM CUSHMAN DAM #2. THE SYSTEM WHICH WILL MOVE THROUGH WESTERN
WASHINGTON MONDAY AFTERNOON AND EVENING IS NOT A FLOOD-PRODUCING
RAIN SYSTEM BUT IT IS A WARM FRONT...SO RIVERS RECEDING WILL
PROBABLY STOP RECEDING AND OLYMPIC RIVERS MIGHT TREND UP FOR A DAY.
THE FRONTAL SYSTEM WED NITE OR THU AND THE CDFNT LATE IN THE WEEK
LOOK RATHER WEAK AND AS IF THEY ARE MOVING INTO A MEAN RIDGE
POSITION. THE SNOW LEVEL WILL PROBABLY TREND DOWN THRU THE WEEK
AFTER PEAKING TUE OR WED. THE BAROCLINIC ZONE THAT GETS HUNG UP ON
VANCOUVER ISLAND WED IS WORTH WATCHING BUT AT THIS TIME I DO NOT SEE
A RISK FOR RIVER FLOODING AND FLOODING IS NOT EXPECTED ON THE GREEN
RIVER IN THE WEEK AHEAD. 19
&&
.AVIATION...STRONG WESTERLY FLOW ALOFT THIS EVENING WILL WEAKEN
OVERNIGHT AS HIGH PRES BUILDS OVER WA. THE ATMOSPHERE WILL REMAIN
STABLE WIND DECREASING MOISTURE AS ONSHORE FLOW WEAKENS. IF PARTIAL
CLEARING DEVELOPS...SHELTERED VALLEYS MAY SEE SOME FOG OVERNIGHT AND
MON MORNING. HOWEVER...A LIGHT BREEZE OVERNIGHT WILL PROBABLY KEEP
WIDESPREAD FOG FROM FORMING.
A CONVERGENCE ZONE WILL LINGER OVER WRN SKAGIT/SNOHOMISH COUNTY THIS
EVENING BEFORE DISSIPATING. SHOWERS AND LOWER CIGS COULD TEMPORARILY
AFFECT KPAE...BUT THE CONVERGENCE ZONE IS NOT EXPECTED TO SAG SOUTH
INTO KING COUNTY.
MOISTURE WILL INCREASE AT ALL LEVELS ON MON AS A FRONT BRINGS RAIN
TO THE COAST DURING THE MORNING...SPREADING INLAND IN THE AFTERNOON.
LIGHT WLY FLOW ALOFT EARLY WILL BECOME STRONG SW FLOW BY LATE
MORNING AS THE FRONT APPROACHES. THE FRONT WILL WEAK CONSIDERABLY AS
IT PUSHES THROUGH PUGET SOUND SOMETIME EARLY MON EVENING.
KSEA...FINALLY SEEING SOME IMPROVEMENT IN CIGS LATE THIS AFTERNOON.
THE LOWER STRATUS DECK SHOULD SCATTER SHORTLY WITH THE 5K FT DECK
POSSIBLY SCATTERING LATER THIS EVENING. MID AND HIGH CLOUDS WILL
INCREASE TOWARD MON MORNING AS THE NEXT SYSTEM OFFSHORE MOVES
CLOSER. THERE SHOULD BE ENOUGH SLY BREEZE TO PREVENT FOG. DTM
&&
.MARINE...ONSHORE FLOW IS STILL STRONG ENOUGH TO WARRANT GALES FOR
THE COAST AND STRAIT. WILL EXTEND THESE THROUGH 9PM THIS EVENING. A
SMALL CRAFT IS UP FOR REMAINING WATERS THIS EVENING. GRADIENTS EASE
LATER THIS EVENING WITH WINDS BELOW 20 KT ACROSS MOST THE WATERS BY
MIDNIGHT.
ANOTHER FRONT WILL BRING POSSIBLE GALES TO THE COAST LATER MON AND
MON EVENING. MODELS KEEP WINDS AT 30 KT OR LESS ACROSS THE NRN
INLAND WATERS WITH MARGINAL SMALL CRAFT IN THE SOUND. THE FRONT
DISSIPATES AS IT PUSHES INLAND MON EVENING SO A STRONG WLY SURGE OF
WIND IN THE STRAIT IS NOT EXPECTED. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
A WINTER STORM WARNING REMAINS EFFECT FOR THE CASCADES TIL 9 PM.
A HIGH SURF ADVISORY IS IN EFFECT FOR THE COAST TIL 9 PM.
PZ...GALE WARNING COAST AND THE ENTIRE STRAIT OF JUAN DE FUCA
THROUGH 9 PM PST.
.SMALL CRAFT ADVISORY UNTIL 9 PM PST REMAINING WATERS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 221750
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PST SUN NOV 22 2009
.SYNOPSIS...A LOW PRESSURE CENTER OVER WASHINGTON WILL SHIFT INLAND
AND HIGHER PRESSURE WILL BUILD INTO THE REGION TODAY. THIS WILL GIVE
RATHER BLUSTERY WINDS...ESPECIALLY ON THE COAST AND IN THE STRAIT OF
JUAN DE FUCA. SNOW SHOWERS WILL BE HEAVY AT TIMES IN THE MOUNTAINS.
A WARM FRONT WILL MOVE THROUGH THE AREA MONDAY AND MONDAY
NIGHT...FOLLOWED BY ANOTHER WARM FRONTAL SYSTEM LATER IN THE WEEK.
&&
.SHORT TERM...ANOTHER BLUSTERY DAY FOR WRN WA...WINDY ON THE COAST
AND THRU THE CHEHALIS GAP...AND WESTERLY GALES SHUD DVLP IN THE
STRAIT BY NOON. THE WIND ADVISORY SHUD PROBABLY BE EXTENDED NORTH
THRU THE METRO AREA AND HOOD CANAL FOR RATHER BLUSTERY WEATHER DVLPG
THRU THE MORNING AND PEAKING MIDDAY. WHEN I DO THAT I WILL HAVE THEM
ALL EXPIRE AT 3PM. SHOULD BE A GOOD PSCZ WIND PATTERN BY
AFTERNOON...SO AFTER THE SURGE OF SW 20-30MPH WINDS THIS MORNING
THRU THE SEATTLE METRO AREA THE WIND WILL SETTLE DOWN AS THE PSCZ
SETS UP. THE WINTER STORM WARNING FOR THE CASCADES PROBABLY NEEDS A
REFRESH AS WELL...IT EXPIRES AT 1PM AND AS THE WESTERLY OROGRAPHIC
SNOW KICKS IN BY AFTERNOON SO THAT NEED TO BE EXTENDED INTO THE
EARLY EVENING. WINDS IN THE CASCADE PASSES INCREASING TO WESTERLY
20-30 MPH BY AFTERNOON AND GUSTS TO 50 ON THE RIDGETOPS...A LOT LESS
THAN THE PEAK WINDS OVERNIGHT: AT THE VERY TOP OF CRYSTAL MOUNTAIN
ARND 1AM LAST NITE STRONG SE WINDS OF 50 MPH GUSTED TO ARND
95MPH...QUITE A WINTER STORM UP HIGH. THE SYSTEM FOR MONDAY WILL BE
WEAKER AND WARMER...ALTHOUGH IT WILL PROBABLY MUSTER SSE GALES JUST
AHEAD OF THE FRONT OVER THE COASTAL WATERS MON MORNING....BY MON
NITE THE GRADIENT OVER WRN WA IS QUITE LIGHT. IN FACT THE WEATHER
PATTERN NEXT WEEK LOOKS A LOT LIKE WHAT EL NINO IS SUPPOSED TO
BRING...WARMTH AND FAIRLY WEAK SYSTEMS. 19
.LONG TERM...ANOTHER WARM FRONT WILL BRUSH THE NORTHWEST CORNER OF
THE AREA AS IT MOVES INTO BRITISH COLUMBIA. THE TRAILING COLD FRONT
WILL DRAG SLOWLY ACROSS THE FORECAST AREA WEDNESDAY NIGHT THROUGH
THURSDAY FOLLOWED BY ITS UPPER TROUGH THURSDAY NIGHT AND FRIDAY.
MCDONNAL
&&
.HYDROLOGY...THE ONLY CURRENT RIVER FLOOD PROBLEM IS THE SKOKOMISH
RIVER. IT IS JUST ABOVE FLOOD STAGE THIS MORNING AND WILL LIKELY
REMAIN ABOVE FLOOD STAGE INTO MONDAY. THIS IS DUE PRIMARILY TO
RELEASES OF WATER FROM CUSHMAN DAM #2. THE SYSTEM MOVING THROUGH
WESTERN WASHINGTON TODAY IS NOT A FLOOD-PRODUCING RAIN SYSTEM BUT
RATHER A HEAVY MOUNTAIN SNOW SYSTEM.
THE FRONTAL SYSTEMS EXPECTED TO ARRIVE DURING THE COMING WEEK WILL
BE ACCOMPANIED BY HIGHER SNOW LEVELS -- PROBABLY IN THE 5000 TO 7000
FT RANGE. ONE FRONT IS FORECAST TO MOVE THROUGH MONDAY AND MONDAY
NIGHT WITH ANOTHER SYSTEM MOVING SLOWLY THROUGH WEDNESDAY NIGHT
THROUGH THURSDAY NIGHT. THEY ARE NOT EXPECTED TO PRODUCE ENOUGH
PRECIPITATION TO CREATE FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER.
&&
.AVIATION...SURFACE LOW PRES THAT MOVED ONSHORE EARLIER THIS MORNING
IS NOW SHIFTING INTO WRN WA ALONG WITH THE UPPER TROUGH. ONSHORE
FLOW WILL PERSIST TODAY WITH STRONG WLY FLOW ALOFT. THE ATMOSPHERE
WILL REMAIN MOIST AND SLIGHTLY UNSTABLE THIS MORNING WITH WRAP
AROUND MOISTURE KEEPING LOWER CIGS AND RAIN AROUND A LITTLE LONGER
THAN EXPECTED. CIGS SHOULD IMPROVE TO VFR AFTER 21Z WITH DECREASING
MOISTURE. WITH PARTIAL CLEARING TONIGHT...EXPECT AREAS OF FOG TO
FORM...MOSTLY IN FAVORED SHELTERED VALLEYS.
A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WILL DEVELOP N OF THE
SNOHOMISH/KING COUNTY BORDER LATER THIS MORNING AND THEN MOVE S
DURING THE AFTERNOON...BECOMING QUASISTATIONARY OVER THE N CENTRAL
PUGET SOUND. AT THIS TIME...IT LOOKS LIKE THE PSCZ WILL REMAIN N OF
KBFI. WINDS WILL BACK TONIGHT AS THE PRES GRADIENT BECOMES SLY...
THUS EXPECT THE PSCZ TO DRIFT BACK TO THE N AND THEN DISSIPATE LATER
TONIGHT.
KSEA...CIGS 1-2K FT AND VIS 3-5SM MAY HOLD IN A LITTLE LONG THAN
EXPECTED DUE TO WRAP AROUND MOISTURE. STILL EXPECT IMPROVEMENT TO
VFR CONDITIONS BY 21Z. SW WIND 10-15 KT W/ GUSTS TO 30 KT
TODAY...BECOMING S 3-6 KT THIS EVENING. DTM
&&
.MARINE...STRONG ONSHORE FLOW TODAY BEHIND A LOW PRESSURE SYSTEM
WHICH IS NOW SHIFTING INTO ERN WA. GALES ALONG THE COAST SHOULD
CONTINUE THROUGH MOST THE DAY BEFORE EASING. THE WINDS IN THE STRAIT
TOOK A LITTLE LONGER THAN EXPECTED TO COME AROUND WLY...BUT SHOULD
STILL POP UP TO GALE FORCE BY NOON. WINDS HAVE COME UP SLIGHTLY
AROUND PUGET SOUND BUT OBS SO FAR ARE FAR SHORT OF GALES...SO I WILL
KEEP A SMALL CRAFT IN EFFECT TODAY. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
A WINTER STORM WARNING REMAINS EFFECT FOR THE CASCADES TODAY.
WIND ADVISORIES ARE IN EFFECT FOR THE STRAIT OF JUAN DE FUCA
AND THE ADMIRALTY INLET AREAS...SOUTHWEST INTERIOR...LOWER
CHEHALIS VALLEY...SEATTLE TACOMA BREMERTON METRO AREA...HOOD
CANAL.
PZ...GALE WARNINGS ARE IN EFFECT FOR ALL WATERS EXCEPT PUGET SOUND
TODAY.
SMALL CRAFT ADVISORY PUGET SOUND TODAY.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS
HARBOR BAR CONDITIONS TIL 4 PM MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 221716
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PST SUN NOV 22 2009
.SYNOPSIS...A LOW PRESSURE CENTER OVER WASHINGTON WILL SHIFT INLAND
AND HIGHER PRESSURE WILL BUILD INTO THE REGION TODAY. THIS WILL GIVE
RATHER BLUSTERY WINDS...ESPECIALLY ON THE COAST AND IN THE STRAIT OF
JUAN DE FUCA. SNOW SHOWERS WILL BE HEAVY AT TIMES IN THE MOUNTAINS.
A WARM FRONT WILL MOVE THROUGH THE AREA MONDAY AND MONDAY
NIGHT...FOLLOWED BY ANOTHER WARM FRONTAL SYSTEM LATER IN THE WEEK.
&&
.SHORT TERM...ANOTHER BLUSTERY DAY FOR WRN WA...WINDY ON THE COAST
AND THRU THE CHEHALIS GAP...AND WESTERLY GALES SHUD DVLP IN THE
STRAIT BY NOON. THE WIND ADVISORY SHUD PROBABLY BE EXTENDED NORTH
THRU THE METRO AREA AND HOOD CANAL FOR RATHER BLUSTERY WEATHER DVLPG
THRU THE MORNING AND PEAKING MIDDAY. WHEN I DO THAT I WILL HAVE THEM
ALL EXPIRE AT 3PM. SHOULD BE A GOOD PSCZ WIND PATTERN BY
AFTERNOON...SO AFTER THE SURGE OF SW 20-30MPH WINDS THIS MORNING
THRU THE SEATTLE METRO AREA THE WIND WILL SETTLE DOWN AS THE PSCZ
SETS UP. THE WINTER STORM WARNING FOR THE CASCADES PROBABLY NEEDS A
REFRESH AS WELL...IT EXPIRES AT 1PM AND AS THE WESTERLY OROGRAPHIC
SNOW KICKS IN BY AFTERNOON SO THAT NEED TO BE EXTENDED INTO THE
EARLY EVENING. WINDS IN THE CASCADE PASSES INCREASING TO WESTERLY
20-30 MPH BY AFTERNOON AND GUSTS TO 50 ON THE RIDGETOPS...A LOT LESS
THAN THE PEAK WINDS OVERNIGHT: AT THE VERY TOP OF CRYSTAL MOUNTAIN
ARND 1AM LAST NITE STRONG SE WINDS OF 50 MPH GUSTED TO ARND
95MPH...QUITE A WINTER STORM UP HIGH. THE SYSTEM FOR MONDAY WILL BE
WEAKER AND WARMER...ALTHOUGH IT WILL PROBABLY MUSTER SSE GALES JUST
AHEAD OF THE FRONT OVER THE COASTAL WATERS MON MORNING....BY MON
NITE THE GRADIENT OVER WRN WA IS QUITE LIGHT. IN FACT THE WEATHER
PATTERN NEXT WEEK LOOKS A LOT LIKE WHAT EL NINO IS SUPPOSED TO
BRING...WARMTH AND FAIRLY WEAK SYSTEMS. 19
.LONG TERM...ANOTHER WARM FRONT WILL BRUSH THE NORTHWEST CORNER OF
THE AREA AS IT MOVES INTO BRITISH COLUMBIA. THE TRAILING COLD FRONT
WILL DRAG SLOWLY ACROSS THE FORECAST AREA WEDNESDAY NIGHT THROUGH
THURSDAY FOLLOWED BY ITS UPPER TROUGH THURSDAY NIGHT AND FRIDAY.
MCDONNAL
&&
.HYDROLOGY...THE ONLY CURRENT RIVER FLOOD PROBLEM IS THE SKOKOMISH
RIVER. IT IS JUST ABOVE FLOOD STAGE THIS MORNING AND WILL LIKELY
REMAIN ABOVE FLOOD STAGE INTO MONDAY. THIS IS DUE PRIMARILY TO
RELEASES OF WATER FROM CUSHMAN DAM #2. THE SYSTEM MOVING THROUGH
WESTERN WASHINGTON TODAY IS NOT A FLOOD-PRODUCING RAIN SYSTEM BUT
RATHER A HEAVY MOUNTAIN SNOW SYSTEM.
THE FRONTAL SYSTEMS EXPECTED TO ARRIVE DURING THE COMING WEEK WILL
BE ACCOMPANIED BY HIGHER SNOW LEVELS -- PROBABLY IN THE 5000 TO 7000
FT RANGE. ONE FRONT IS FORECAST TO MOVE THROUGH MONDAY AND MONDAY
NIGHT WITH ANOTHER SYSTEM MOVING SLOWLY THROUGH WEDNESDAY NIGHT
THROUGH THURSDAY NIGHT. THEY ARE NOT EXPECTED TO PRODUCE ENOUGH
PRECIPITATION TO CREATE FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER.
&&
.AVIATION...SURFACE LOW PRES THAT MOVED ONSHORE EARLIER THIS MORNING
IS NOW SHIFTING INTO WRN WA ALONG WITH THE UPPER TROUGH. ONSHORE
FLOW WILL PERSIST TODAY WITH STRONG WLY FLOW ALOFT. THE ATMOSPHERE
WILL REMAIN MOIST AND SLIGHTLY UNSTABLE THIS MORNING WITH WRAP
AROUND MOISTURE KEEPING LOWER CIGS AND RAIN AROUND A LITTLE LONGER
THAN EXPECTED. CIGS SHOULD IMPROVE TO VFR AFTER 21Z WITH DECREASING
MOISTURE. WITH PARTIAL CLEARING TONIGHT...EXPECT AREAS OF FOG TO
FORM...MOSTLY IN FAVORED SHELTERED VALLEYS.
A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WILL DEVELOP N OF THE
SNOHOMISH/KING COUNTY BORDER LATER THIS MORNING AND THEN MOVE S
DURING THE AFTERNOON...BECOMING QUASISTATIONARY OVER THE N CENTRAL
PUGET SOUND. AT THIS TIME...IT LOOKS LIKE THE PSCZ WILL REMAIN N OF
KBFI. WINDS WILL BACK TONIGHT AS THE PRES GRADIENT BECOMES SLY...
THUS EXPECT THE PSCZ TO DRIFT BACK TO THE N AND THEN DISSIPATE LATER
TONIGHT.
KSEA...CIGS 1-2K FT AND VIS 3-5SM MAY HOLD IN A LITTLE LONG THAN
EXPECTED DUE TO WRAP AROUND MOISTURE. STILL EXPECT IMPROVEMENT TO
VFR CONDITIONS BY 21Z. SW WIND 10-15 KT W/ GUSTS TO 30 KT
TODAY...BECOMING S 3-6 KT THIS EVENING. DTM
&&
.MARINE...STRONG ONSHORE FLOW TODAY BEHIND A LOW PRESSURE SYSTEM
WHICH IS NOT SHIFTING INTO ERN WA. GALES ALONG THE COAST SHOULD
CONTINUE THROUGH MOST THE DAY BEFORE EASING. THE WINDS IN THE STRAIT
TOOK A LITTLE LONGER THAN EXPECTED TO COME AROUND WLY...BUT SHOULD
STILL POP UP TO GALE FORCE BY NOON. WINDS HAVE COME UP SLIGHTLY
AROUND PUGET SOUND BUT OBS SO FAR ARE FAR SHORT OF GALES...SO I WILL
KEEP A SMALL CRAFT IN EFFECT TODAY. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER
IN MASON COUNTY.
A WINTER STORM WARNING REMAINS EFFECT FOR THE CASCADES TODAY.
WIND ADVISORIES ARE IN EFFECT FOR THE STRAIT OF JUAN DE FUCA
AND THE ADMIRALTY INLET AREAS...SOUTHWEST INTERIOR...LOWER
CHEHALIS VALLEY...SEATTLE TACOMA BREMERTON METRO AREA...HOOD
CANAL.
PZ...GALE WARNINGS ARE IN EFFECT FOR ALL WATERS EXCEPT PUGET SOUND
TODAY.
SMALL CRAFT ADVISORY PUGET SOUND TODAY.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS
HARBOR BAR CONDITIONS TIL 4 PM MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 221210
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST SUN NOV 22 2009
.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM IS MOVING THROUGH THE PACIFIC
NORTHWEST THIS MORNING. ITS SURFACE LOW MADE LANDFALL NEAR ASTORIA
OVERNIGHT AND IT WILL MOVE QUICKLY NORTHEAST ACROSS THE CASCADES
THIS MORNING. THE SYSTEM WILL BRING A COOL SHOWERY DAY WITH SNOW IN
THE MOUNTAINS. A WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND
MONDAY NIGHT...FOLLOWED BY WEAK FRONT LATE IN THE WEEK.
&&
.SHORT TERM...A VIGOROUS FRONTAL SYSTEM IS MAKING ITS THROUGH THE
PACIFIC NORTHWEST THIS MORNING...BRINGING SIGNIFICANT RAIN TO THE
LOWLANDS AND HEAVY SNOW TO THE MOUNTAINS. THE 989 MB SURFACE LOW
MADE LANDFALL NEAR ASTORIA AROUND 2 AM AND IT IS MOVING QUICKLY
EAST-NORTHEAST ACROSS THE SOUTH INTERIOR OF WESTERN WASHINGTON. THE
MAIN FRONTAL PRECIPITATION BAND BROUGHT SIGNIFICANT RAIN TO THE
LOWLANDS...AND WE RECEIVED SOME REPORTS OF WET SNOW FALLING TO NEAR
SEA LEVEL ALONG HOOD CANAL. AT 3 AM THE PRECIPITATION BAND HAD MOVED
INTO THE NORTH PART OF THE FORECAST AREA...AND LOWLAND TEMPERATURES
WERE IN THE MID 30S TO MID 40S.
THE WIND HAS BEEN THE REALLY DIFFICULT PART OF THE FORECAST WITH
THIS SYSTEM...DUE TO UNCERTAINTY WITH REGARD TO THE TRACK OF THE
SURFACE LOW. THE 06Z NAM12 MODEL LOOKS TO HAVE THE BEST HANDLE ON
THE LOW RIGHT NOW...SHOWING THAT IT WILL CONTINUE ITS EAST-NORTHEAST
TRACK AND CROSS THE CENTRAL CASCADES BEFORE 10 AM. IT LOOKS
INCREASINGLY LIKELY THAT WINDS MEETING HIGH WIND WARNING CRITERIA --
THAT IS SUSTAINED 40 MPH AND/OR GUSTS 60 MPH -- WILL NOT MATERIALIZE
...DUE PRIMARILY TO THE LOW BEING FURTHER SOUTH THAN PREVIOUSLY
ANTICIPATED. THERE WILL BE WINDY CONDITIONS MAINLY ALONG THE STRAIT
OF JUAN DE FUCA AND ADMIRALTY INLET...AND ALONG THE CENTRAL COAST
AND THROUGH THE LOWER CHEHALIS VALLEY AND SOUTHWEST INTERIOR BEHIND
THE SURFACE LOW. THE HIGH WIND WARNINGS WILL BE DROPPED WITH THE
EARLY MORNING FORECAST PACKAGE.
A WINTER STORM WARNING FOR HEAVY SNOW WILL CONTINUE FOR THE CASCADES
THROUGH 1 PM TODAY...WHILE THE WARNING FOR THE OLYMPICS IS DUE TO
EXPIRE AT 4 AM. THIS LOOKS ON TRACK. ANOTHER 8 TO 16 INCHES OF SNOW
IS LIKELY IN THE CASCADES TODAY...MOST OF IT FALLING THIS MORNING.
ANOTHER 4 TO 8 INCHES IS LIKELY IN THE OLYMPICS.
PRECIPITATION OVER THE WESTERN WASHINGTON LOWLANDS WILL BE SHOWERY
TODAY IN THE WAKE OF THE FRONT...GENERALLY TAPERING OFF DURING THE
AFTERNOON. HOWEVER A PUGET SOUND CONVERGENCE ZONE WILL LIKELY
DEVELOP AND CONTINUE THROUGH THIS EVENING.
A LESS EVENTFUL STRETCH OF WEATHER LOOKS LIKELY BEGINNING TONIGHT
AND CONTINUING THROUGH THE END OF THE WEEK. AN UPPER RIDGE WILL
PROGRESS ACROSS THE FORECAST AREA TONIGHT AND THE NEXT FRONTAL
SYSTEM UPSTREAM -- CURRENTLY OUT ALONG 150W -- WILL APPROACH THE
FORECAST AREA MONDAY. ITS WARM FRONT WILL BRING PRECIPITATION TO THE
OLYMPIC PENINSULA MONDAY MORNING...AND WIDESPREAD PRECIPITATION WILL
SPREAD INLAND LATER MONDAY AND MONDAY NIGHT AS THE COLD FRONT MOVES
THROUGH. A STRONGER RIDGE WILL MOVE OVER WESTERN WASHINGTON TUESDAY
WITH 500 MB HEIGHTS CLIMBING TO AROUND 5700 METERS. MCDONNAL
.LONG TERM...THE UPPER RIDGE MENTIONED ABOVE WILL HEAD EAST OF THE
CASCADES TUESDAY NIGHT...AND ANOTHER WARM FRONT WILL BRUSH THE
NORTHWEST CORNER OF THE AREA AS IT MOVES INTO BRITISH COLUMBIA. THE
TRAILING COLD FRONT WILL DRAG SLOWLY ACROSS THE FORECAST AREA
WEDNESDAY NIGHT THROUGH THURSDAY FOLLOWED BY ITS UPPER TROUGH
THURSDAY NIGHT AND FRIDAY. MCDONNAL
&&
.HYDROLOGY...THE ONLY CURRENT RIVER FLOOD PROBLEM IS THE SKOKOMISH
RIVER. IT IS JUST ABOVE FLOOD STAGE THIS MORNING AND WILL LIKELY
REMAIN ABOVE FLOOD STAGE INTO MONDAY. THIS IS DUE PRIMARILY TO
RELEASES OF WATER FROM CUSHMAN DAM #2. THE SYSTEM MOVING THROUGH
WESTERN WASHINGTON TODAY IS NOT A FLOOD-PRODUCING RAIN SYSTEM BUT
RATHER A HEAVY MOUNTAIN SNOW SYSTEM.
THE FRONTAL SYSTEMS EXPECTED TO ARRIVE DURING THE COMING WEEK WILL
BE ACCOMPANIED BY HIGHER SNOW LEVELS -- PROBABLY IN THE 5000 TO 7000
FT RANGE. ONE FRONT IS FORECAST TO MOVE THROUGH MONDAY AND MONDAY
NIGHT WITH ANOTHER SYSTEM MOVING SLOWLY THROUGH WEDNESDAY NIGHT
THROUGH THURSDAY NIGHT. THEY ARE NOT EXPECTED TO PRODUCE ENOUGH
PRECIPITATION TO CREATE FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER.
&&
.AVIATION...AN UPPER LOW OVER SW WASHINGTON WILL CONTINUE MOVING E.
EXPECT AN UPPER RIDGE TO MOVE OVER THE REGION TONIGHT BEHIND THIS
SYSTEM. ELY FLOW ALOFT WILL BECOME NLY THIS AFTERNOON...AND THEN WLY
OVERNIGHT.
THE STRONG...SFC LOW THAT DEVELOPED OFF THE FAR NORTHERN OREGON
COAST MOVED INLAND...OVER THE MOUTH OF THE COLUMBIA RIVER...ABOUT
10Z. THIS LOW NOW APPEARED TO BE NEAR KKLS AND WAS CONTINUING TO
MOVE E. EXPECT STRONG ONSHORE FLOW TO DEVELOP BY LATE THIS MORNING
IN THE WAKE OF THIS FEATURE. THE STRONGEST WINDS WILL LIKELY OCCUR
OVER THE COAST AND ADMIRALTY INLET AREA. EXPECT THE FLOW TO WEAKEN
OVERNIGHT.
A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WILL DEVELOP N OF THE
SNOHOMISH/KING COUNTY BORDER LATER THIS MORNING AND THEN MOVE S
DURING THE AFTERNOON...BECOMING QUASISTATIONARY OVER THE N CENTRAL
PUGET SOUND. AT THIS TIME...IT LOOKS LIKE THE PSCZ WILL REMAIN N OF
KBFI. WINDS WILL BACK TONIGHT AS THE PRES GRADIENT BECOMES SLY...
THUS EXPECT THE PSCZ TO DRIFT BACK TO THE N AND THEN DISSIPATE LATER
TONIGHT.
CIGS WILL GENERALLY BE IN THE 4-7K FT RANGE TODAY. EXPECT THE LOWER
CLOUD DECK TO BECOME SCATTERED THIS EVENING BUT THERE WILL BE AN
INCREASE IN HIGH LEVEL MOISTURE...ABOVE 15K FT...OVERNIGHT. EXPECT
LOCALIZED FOG...REDUCING VSBYS INTO 3-5SM...TO DEVELOP LATER
TONIGHT...BUT MAINLY IN THE FAVORED RIVER VALLEYS.
KSEA...ELY WINDS WILL DROP OFF BY MIDMORNING AND THEN KICK UP FROM
THE SW LATER THIS MORNING. CIGS WILL MAINLY BE IN THE 5-6K FT
RANGE...ALTHOUGH THE CLOUDS WILL BECOME SCATTERED LATER TODAY...IF
NOT EARLIER.
&&
.MARINE...STRONG WESTERLY FLOW WILL DEVELOP IN THE WAKE OF A 985 MB
LOW THAT MOVED INLAND EARLIER. THIS WILL RESULT IN GALE FORCE
WESTERLY WINDS OVER MUCH OF THE AREA...WITH A BRIEF PERIOD OF STORM
FORCE WINDS POSSIBLE OVER THE CENTRAL STRAIT OF JUAN DE FUCA THIS
MORNING. THE ONSHORE FLOW WILL WEAKEN TONIGHT. ANOTHER...BUT
WEAKER...FRONTAL SYSTEM WILL AFFECT THE AREA ON MON. EXPECT OFFSHORE
FLOW TO DEVELOP ON TUE.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A FLOOD WARNING REMAINS IN EFFECT FOR THE SKOKOMISH RIVER IN
MASON COUNTY.
A WINTER STORM WARNING REMAINS EFFECT FOR THE CASCADES TIL
1 PM TODAY.
A WIND ADVISORY IS IN EFFECT FOR THE ADMIRALTY INLET AREA...
SOUTHWEST INTERIOR...LOWER CHEHALIS VALLEY...AND STRAIT OF JUAN
DE FUCA.
PZ...GALE WARNINGS ARE IN EFFECT FOR ALL WATERS TIL 4 PM TODAY.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS
HARBOR BAR CONDITIONS TIL 4 PM MON.
$$
WWW.WEATHER.GOV/SEATTLE
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000
FXUS66 KSEW 220530
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PST SAT NOV 21 2009
.SYNOPSIS...A DEEP LOW PRESSURE SYSTEM WILL MOVE INLAND ACROSS
SOUTHERN PORTIONS OF THE AREA LATE TONIGHT AND EARLY SUNDAY MORNING
BRINGING STRONG WINDS...RAIN AND HEAVY MOUNTAIN SNOW TO THE AREA. A
WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND MONDAY NIGHT. YET
ANOTHER WEAK FRONT WILL MOVE ACROSS THE AREA LATER IN THE WEEK.
&&
.SHORT TERM...THE MAIN ISSUES ARE IN THE SHORT TERM PERIOD...TONIGHT
AND EARLY SUNDAY...AS A DEEPENING LOW PRESSURE SYSTEM IN THE
NORTHERN OREGON OFFSHORE WATERS WINDS UP AND HEADS TOWARD THE
CENTRAL WASHINGTON COAST LATE TONIGHT. WITH A LACK OF BUOYS OR SHIP
REPORTS IN THE REGION OF STRONG CYCLOGENESIS...IT IS DIFFICULT TO
GET A FEEL FOR HOW STRONG THE SYSTEM IS AT THIS TIME. BUT INFRARED
IMAGERY APPEARS TO BE SHOWING THE DEVELOPMENT OF A CIRCULATION
CENTER IN THE VICINITY OF WHERE BUOY 46005 SHOULD
BE...45.7N/129W...THE PERIPHERY OF THE CENTER APPEARS TO SHOW GOOD
INSTABILITY WITH LOW TOPPED CONVECTION PARTIALLY RINGING IT...AND
THERE APPEARS TO BE HINTS AT THE DEVELOPMENT OF A BENT BACK
OCCLUSION TO THE WEST OF THE CENTER THAT APPEARS TO BE GETTING READY
TO PIVOT AROUND THE SW PORTION OF THE CENTER. WATER VAPOR IMAGERY
SHOWS GOOD DARKENING. 300 MB WINDS ALOFT SHOW VERY STRONG DIFFLUENCE
IN THE LEFT EXIT REGION OF A 150-170 KT ESE DIRECTED JET STREAK TO
THE WEST OF THE DEVELOPING CENTER. THE LATEST 00Z 12KM NAM AGREES
WITH EARLIER SOLUTIONS AND WITH THE 12Z 4KM MM5WRF AND THE INCOMING
00Z MM5NAM SOLUTIONS. THIS WOULD TAKE THE CENTER ONTO THE CENTRAL
COAST NEAR HOQUIAM BETWEEN 09Z AND 12Z THEN TAKE IT RAPIDLY EAST
THRU THE CHEHALIS GAP TO THE SOUTH PUGET SOUND AND INTO THE CENTRAL
CASCADES. THE GFS SOLUTIONS APPEAR MUSHED OUT AND TOO FAR NORTH WITH
THE CIRCULATION CENTER.
CONCERNING WIND...CURRENT WARNINGS AND ADVISORIES LOOK GOOD WITH
HIGH WIND WARNINGS ON THE CENTRAL COAST...IN THE ADMIRALTY INLET
AREA...AND IN THE CHEHALIS GAP AND SOUTHWEST INTERIOR WHERE THESE
AREAS WILL SEE STRONG SLY/SELY WINDS AHEAD OF THE LOW AND A PERIOD
OF STRONG W/NW WINDS BEHIND THE LOW. IN THE NORTHWEST INTERIOR ZONES
AROUND WESTERN WHATCOM COUNTY...THE SAN JUANS...AND WESTERN SKAGIT
COUNTY...HIGH WIND WARNINGS WILL EXPIRE AT MIDNIGHT AND ARE BEING
CAUSED BY A WARM FRONT OUT AHEAD OF THE DEVELOPING LOW. MANY AREAS
WILL SEE A BRIEF LULL IN THE WINDS AS THE BACK AROUND TO E/NE AHEAD
OF THE LOW...THEN SEE A VERY RAPID SURGE FROM THE WEST BEHIND THE
LOW. WILL KEEP AN EYE ON SATELLITE IMAGERY...IF THE STRENGTH OR
TRACK OF THE LOW CHANGES...WE MAY NEED TO UPGRADE SOME OF THE WIND
ADVISORIES TO WARNINGS. THE POST-LOW STRONG WINDS WILL NOT LAST
LONG...ONLY 3-4 HOURS OR SO AND WINDS ALL AREAS SHOULD RAPIDLY
DIMINISH AFTER 10 AM.
CONCERNING WINTER WEATHER...SNOW IS PICKING UP AT PARADISE RANGER
STATION AT MT RAINIER...BUT MOST PLACES HAVE YET TO REPORT MORE THAN
AN INCH OR TWO OVER THE PAST SEVERAL HOURS. EXPECT SNOWFALL RATES TO
PICK UP AS THE LOW APPROACHES...THEN CONTINUE FOR A FEW HOURS BEHIND
THE LOW WITH STRONG ONSHORE FLOW. THE WINTER STORM WARNINGS FOR THE
MOUNTAINS WILL BE CONTINUED...FOR THE COMBINATION OF SNOW AND WIND.
IF SNOWFALL RATES DONT PICK UP BY 10 PM...WE WILL UPDATE THE WARNING
FOR LOWER SNOW AMOUNTS...BUT STRONG WIND AND VERY LOW VISIBILITY FOR
A COUPLE HOURS AROUND THE PASSAGE OF THE LOW WILL STILL PRODUCE NEAR
BLIZZARD CONDITIONS IN THE MOUNTAINS LATE TONIGHT OR EARLY SUNDAY.
FLOW BEHIND THE SYSTEM APPEARS TOO STRONG TO PRODUCE A CONVERGENCE
ZONE SUNDAY...AND EXPECT SOME DRY AIR TO MIX DOWN WITH THE PASSING
JET STREAK SUNDAY. A BRIEF WEAK RIDGE OF HIGH PRES MOVES ACROSS THE
AREA SUN NIGHT. A WEAKER FRONTAL SYSTEM WILL PASS ACROSS THE AREA
LATER MON OR MON NIGHT. TUE AND TUE NIGHT NOW LOOK MORE TRANQUIL.
ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...A WEAK UPPER
RIDGE WILL SETTLE IN OVER THE REGION TUESDAY AND WEDNESDAY WITH A
CHANCE OF RAIN IN THE FORECAST FOR TUESDAY AND WEDNESDAY. A WEAK
FRONT WILL SLOWLY MOVE ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT AND
THURSDAY. THIS SYSTEM LOOKS TO BRING MORE PRECIPITATION TO THE AREA
THAN MONDAYS WEAK SYSTEM...MOSTLY DUE TO ITS SLOW TRANSITION ACROSS
WESTERN WASHINGTON...WHICH MIGHT BEAR SOME WATCHING AS WE MOVE INTO
EARLY NEXT WEEK. MEDIUM RANGE MODELS IN A BIT MORE AGREEMENT ON THE
FRONTAL WAVE THAT SLIDES INTO THE AREA THURSDAY NIGHT AND FRIDAY.
&&
.HYDROLOGY...THE ONLY HYDROLOGICALLY IMPORTANT PRECIPITATION THIS
EVENING IS TAKING PLACE AT LOWER ELEVATIONS OVER THE OLYMPIC
PENINSULA WHERE ABOUT 1-1.5 INCHES OF RAIN APPEARS TO HAVE FALLEN
SINCE ABOUT 21Z. ELSEWHERE PRECIPITATION HAS BEEN LIGHTER AND SNOW
LEVELS ARE BELOW 3000 FT. EXPECT OCCASIONALLY HEAVY RAIN TO CONTINUE
UNTIL THE LOW PASSES AROUND 12Z.
THE SKOKOMISH RIVER IS THE ONLY RIVER FLOODING AT THIS TIME. IT ROSE
BACK ABOVE FLOOD STAGE LATE THIS AFTERNOON PARTIALLY DUE TO RAINFALL
AND ALSO DUE TO PLANNED RELEASES TO 3000 CFS FROM CUSHMAN DAM NUMBER
2. IT WILL CREST AROUND 14Z SUNDAY AT ABOUT 16.9 FT...THEN FALL
SLOWLY THRU MONDAY. WITH COLDER CONDITIONS ALOFT AT THIS TIME AND
SOMEWHAT DRIER CONDITIONS OVER THE NEXT SEVERAL DAYS WITH
WEAKER...COOLER...AND PROGRESSIVE FRONTAL SYSTEMS AND LONGER BREAKS
BETWEEN SYSTEMS...OTHER RIVERS ACROSS WESTERN WASHINGTON SHOULD
REMAIN BELOW FLOOD STAGE FOR THE NEXT SEVERAL DAYS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. ALBRECHT
&&
.AVIATION...AN UPPER TROF WILL MOVE ACROSS THE AREA OVERNIGHT...AND
THEN OVER THE GREAT BASIN SUNDAY AFTERNOON. STRONG SW FLOW ALOFT...
BECOMING NW ON SUNDAY. A SURFACE LOW NOW ABOUT 175 MILES W OF THE
NRN OREGON COAST WILL CONTINUE MOVING RAPIDLY ENE. THIS LOW IS
EXPECTED TO TRACK OVER THE FAR S PUGET SOUND OR JUST S OF IT LATE
TONIGHT. STRONG ONSHORE OR WLY FLOW WILL THEN DEVELOP IN ITS WAKE.
MOIST AIR MASS WILL REMAIN OVER THE AREA...WITH CIGS MAINLY IN THE
1-3K FT RANGE...LIFTING INTO THE 4-6K FT RANGE SUNDAY. THE AIR MASS
WILL BECOME SLIGHTLY UNSTABLE ON SUNDAY FOR A SLIGHT CHANCE...ABOUT
10 PERCENT...OF TSTMS. A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WILL
ALSO DEVELOP SUNDAY MORNING...NORTH OF THE SNOHOMISH/KING COUNTY
BORDER...AND THEN DRIFT S TO N OF KBFI IN THE AFTERNOON.
KSEA...WIND ABOVE THE SFC HAVE BACKED AROUND AND DROPPED OFF FASTER
THAN THE MODELS INDICATED...THUS IT APPEARED THAT LLWS WILL NO
LONGER BE A PROBLEM IN THE NEAR TERM. EXPECT WINDS TO INCREASE
DRAMATICALLY FROM THE SW ABOUT 12Z...IF THE SFC LOW TRACKS OVER THE
S SOUND. IF THE SFC LOW TRACKS FARTHER S...WINDS WILL BE LIGHT AND
VARIABLE OR LIGHT NLY...BEFORE KICKING UP OUT OF THE SW LATER IN THE
MORNING.
&&
.MARINE...AN OCCLUDED FRONT...EXTENDING FROM A NEAR 990 MB LOW S OF
THE QUEEN CHARLOTTES...WAS OFFSHORE. THIS FRONT WILL WEAKEN AND
SWING ACROSS THE NORTHERN WATERS OVERNIGHT. MEANWHILE...A RAPIDLY
DEEPENING LOW NOW ABOUT 150 NM OFF THE NORTHERN OREGON COAST WILL
MOVE ACROSS THE CENTRAL COASTAL WATERS AND FAR SOUTH PUGET SOUND
LATE TONIGHT. THIS LOW WILL RESULT IN STORM FORCE SOUTH WINDS OVER
THE CENTRAL COASTAL WATERS TONIGHT. EXPECT STRONG WESTERLY FLOW TO
DEVELOP EARLY SUNDAY FOR GALE FORCE WESTERLY WINDS ACROSS A PORTION
OF THE WATERS. A BRIEF PERIOD OF STORM FORCE WINDS MAY OCCUR OVER
THE CENTRAL STRAIT OF JUAN DE FUCA SUNDAY MORNING WITH THE INITIAL
PUSH. THE ONSHORE FLOW WILL WEAKEN SUNDAY NIGHT.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS REMAIN IN EFFECT FOR PORTIONS OF WESTERN
WASHINGTON.
.WINTER STORM WARNING IN EFFECT FOR THE OLYMPIC MOUNTAINS
UNTIL 4 AM PST SUNDAY AND FOR THE CASCADES FROM UNTIL
1 PM PST SUNDAY.
.HIGH WIND WARNING FOR THE CENTRAL WASHINGTON COAST...THE
LOWER CHEHALIS VALLEY...SOUTHWEST INTERIOR AND
ADMIRALTY INLET AREA THROUGH 10 AM SUNDAY.
.HIGH WIND WARNING FOR THE NORTH INTERIOR OF WESTERN
WASHINGTON THROUGH MIDNIGHT TONIGHT.
.WIND ADVISORY FOR THE CENTRAL PUGET SOUND AREA AND STRAIT
OF JUAN DE FUCA ZONES MIDNIGHT TONIGHT THROUGH SUNDAY
MORNING.
PZ...A STORM WARNING IS IN EFFECT FOR THE CENTRAL COASTAL WATERS
WATERS UNTIL 1 AM SUNDAY.
.GALE WARNINGS ARE IN EFFECT FOR THE REMAINING WATERS.
.A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR
CONDITIONS IS IN EFFECT TIL 4 PM MON.
$$
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000
FXUS66 KSEW 212357 AAA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
400 PM PST SAT NOV 21 2009
.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL MOVE THROUGH WESTERN
WASHINGTON THIS AFTERNOON AND EVENING BRINGING STRONG WINDS...RAIN
AND HEAVY MOUNTAIN SNOW TO THE AREA INTO SUNDAY. A WEAKER FRONT WILL
MOVE THROUGH THE AREA MONDAY AND MONDAY NIGHT...AND ANOTHER WEAK
FRONT WILL LATER IN THE WEEK.
&&
.SHORT TERM...A WARM FRONT WILL LIFT ACROSS WESTERN WASHINGTON EARLY
THIS EVENING FOLLOWED BY AN OCCLUDED FRONT AND SURFACE LOW LATE
TONIGHT INTO THURSDAY MORNING. MESOSCALE MODELS ADVERTISING A MORE
SOUTHERLY TRACK FOR THE THE SURFACE LOW...MOVING ONSHORE NEAR KHQM
JUST AFTER MIDNIGHT TONIGHT...THEN NORTHEAST INTO THE SOUTH SOUND
AND THEN EAST OF THE CASCADES BY LATE SUNDAY MORNING. THIS
WILL PRODUCE WINDY CONDITIONS ACROSS THE AREA. STRONGEST WINDS WILL
LIKELY COME AS A ONE TWO PUNCH WITH THE SOUTHERLIES AHEAD OF THE LOW
AND OCCLUDED FRONT TONIGHT...AND AGAIN WITH THE WESTERLIES BEHIND
THE LOW AND FRONT AS THEY TRACK INLAND EARLY SUNDAY MORNING. SOME
AREAS LIKE THE COAST...ADMIRALTY INLET...NORTH INTERIOR WILL
EXPERIENCE BOTH PERIODS OF STRONG WINDS...MOST OTHER AREAS WILL
EXPERIENCE THE STRONGEST WINDS WITH AND BEHIND THE FRONT LATE
TONIGHT INTO EARLY SUNDAY MORNING. WINDS SHOULD BEGIN TO COME DOWN
BY LATE SUNDAY MORNING AND INTO THE AFTERNOON HOURS ALL AREAS.
THE SNOW LEVEL WILL CONTINUE TO RISE TO AROUND 3000 FT TONIGHT AS
THE WARM FRONT LIFTS OVER THE AREA...FALLING AGAIN TO AROUND 2000 FT
TOMORROW MORNING AS THE OCCLUDED FRONT PUSHES THROUGH. BOTH FRONTS
WILL BRING SIGNIFICANT PRECIPITATION TO THE COAST...OLYMPICS AND
CASCADES TONIGHT THROUGH SUNDAY MORNING. HEAVY SNOW FOR THE
MOUNTAINS REMAINS ON TRACK WITH IMPRESSIVE PRECIPITATION AMOUNTS
THROUGH SUNDAY MORNING FOR THE OLYMPICS...3 TO 4 INCHES...AND THE
CASCADES...1 TO 3 INCHES. EVEN WITH THE RISE OF SNOW LEVELS TO
AROUND 3000 FT...30 TO 40 INCHES OF SNOW ARE EXPECTED FOR THE
OLYMPICS AND 10 TO 30 INCHES FOR THE CASCADES. EVEN THE RELATIVELY
DRIER HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS.
FLOW IS STRONG ENOUGH THROUGH THE DAY TOMORROW THAT CONVERGENCE ZONE
IS UNLIKELY...WITH MOST OF THE POST-FRONTAL SHOWERS PUSHED UP ONTO
THE MOUNTAINS. SHOWERS WILL TAPER OFF SUNDAY AFTERNOON EVENING AS
THE UPPER RIDGE MOVES OVERHEAD. THE RIDGE KICKS EAST QUICKLY MONDAY
AHEAD OF ANOTHER FRONTAL SYSTEM. THIS NEXT SYSTEM COULD STILL BRING
DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC PENINSULA
MONDAY AFTERNOON...BUT WEAKENS AS IT MOVES INLAND MONDAY NIGHT.
COMPARED TO LAST SEVERAL SYSTEMS THIS WILL BE AN UNEVENTFUL
SYSTEM...MARKING THE BEGINNING OF A PERIOD OF QUIETER WEATHER. COOK
.LONG TERM...A WEAK UPPER RIDGE WILL SETTLE IN OVER THE REGION
TUESDAY AND WEDNESDAY WITH A CHANCE OF RAIN IN THE FORECAST FOR
TUESDAY AND WEDNESDAY. A WEAK FRONT WILL SLOWLY MOVE ACROSS WESTERN
WASHINGTON WEDNESDAY NIGHT AND THURSDAY. THIS SYSTEM LOOKS TO BRING
MORE PRECIPITATION TO THE AREA THAN MONDAYS WEAK SYSTEM...MOSTLY DUE
TO ITS SLOW TRANSITION ACROSS WESTERN WASHINGTON...WHICH MIGHT BEAR
SOME WATCHING AS WE MOVE INTO EARLY NEXT WEEK. MEDIUM RANGE MODELS
IN A BIT MORE AGREEMENT ON THE FRONTAL WAVE THAT SLIDES INTO THE
AREA THURSDAY NIGHT AND FRIDAY.
&&
.HYDROLOGY...TODAYS SYSTEM WILL BRING IMPRESSIVE AMOUNTS OF
PRECIPITATION TO THE CASCADES AND OLYMPICS...BUT RELATIVELY LOW SNOW
LEVELS WILL MITIGATE THE IMPACT ON WESTERN WASHINGTON RIVERS EXCEPT
THE SKOKOMISH RIVER WHICH IS ALREADY AT OR NEAR FLOOD STAGE GOING
INTO THIS EVENT. THE SNOW LEVEL WILL ONLY RISING TO AROUND 3000 FT
TONIGHT...AND THEN FALL SUNDAY TO AROUND 2000 FT...MAKING THIS
MOSTLY A MOUNTAIN SNOW EVENT AND NOT A RAIN EVENT.
THE SKOKOMISH RIVER FELL TO JUST BELOW FLOOD STAGE EARLY SATURDAY
AFTERNOON. NEW FORECAST GUIDANCE SHOWS THE RIVER RISING AGAIN TO
JUST BELOW 17 FEET BY EARLY SUNDAY MORNING. IN ADDITION...THERE HAS
BEEN PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM #2 INTO THE NORTH
FORK SKOKOMISH RIVER THIS AFTERNOON. HAVE ACCORDINGLY EXTENDED THE
WARNING FOR THE SKOKOMISH INTO MONDAY.
GUIDANCE AND OBSERVATIONS FOR THE LOWER REACH OF THE CHEHALIS RIVER
IN GRAYS HARBOR COUNTY CONTINUE TO SUPPORT THE IDEA THAT IT WILL
REMAIN WELL BELOW FLOOD STAGE SO HAVE ACCORDINGLY ENDED THE FLOOD
WATCH.
MONDAYS WEAKER SYSTEM LOOKS TO BE PROGRESSIVE ENOUGH TO BE OF LITTLE
CONCERN WITH RESPECT TO FLOODING. THE AIR MASS OVER THE NORTHWEST
FOR THE REMAINDER OF THE WEEK WILL BE WARMER WITH HIGHER SNOW
LEVELS...HOWEVER THE SYSTEMS THAT ARE EXPECTED TO AFFECT THE AREA
WILL BE FAIRLY WEAK AND ARE NOT EXPECTED TO CAUSE ANY ADDITIONAL
FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. COOK
&&
.AVIATION...A WARM/OCCLUDED FRONT JUST OFFSHORE THIS AFTERNOON WILL
LIFT ACROSS WRN WA EARLY THIS EVENING. SLY FLOW ALOFT WILL BECOME
STRONG. THE ATMOSPHERE WILL BE STABLE AND MOIST WITH RAIN INCREASING
ACROSS THE AREA. SURFACE GRADIENTS BECOME MORE ELY OVERNIGHT WITH
STRONG SLY FLOW JUST OFF THE SURFACE CREATING THE POTENTIAL FOR
LLWS. TAFS WERE UPDATED EARLIER TO INCLUDE THIS FOR MOST
TERMINALS...GENERALLY IN THE 02Z-12Z TIME FRAME.
SURFACE LOW PRESSURE WILL DEEPEN TO AROUND 985-990 MB TONIGHT AND
TRACK INTO SRN WA NEAR KHQM ARND 12Z. STRONG PRESSURE RISES ARE
EXPECTED BEHIND THE LOW FROM THE CENTRAL COAST EWD INTO THE SW
INTERIOR WHICH WILL RESULT IN A BURST OF STRONG WINDS SOMETIME
BETWEEN 12-16Z SUN MORNING. THE ATMOSPHERE WILL BE SOMEWHAT UNSTABLE
NEAR THE LOW CENTER...ALLOWING WINDS ALOFT TO MIX DOWN TO THE
SURFACE IN GUSTS. A BURST OF WIND DOWN THE STRAIT WILL ALSO DEVELOP
SUN MORNING.
KSEA...LLWS IS POSSIBLE FROM AROUND 02Z-12Z AS SURFACE GRADIENTS
BECOME ELY AND SLY FLOW OF 30-40 KT DEVELOPS AROUND 2K FT.
OTHERWISE...RAIN WILL INCREASE THIS EVENING WITH MVFR CONDITIONS
EXPECTED. SLY WINDS AROUND 10 KT THROUGH TONIGHT...BUT A DRAMATIC
JUMP IN SW WINDS IS ANTICIPATED AFTER 12Z AS A SURFACE LOW TRACKS
INLAND NEAR OR SOUTH OF KSEA. SW WINDS OF 20-30 KT WITH HIGHER GUSTS
ARE POSSIBLE FROM 12-16Z. DTM
&&
.MARINE...WINDS ARE SLOWLY PICKING UP ACROSS WRN WA IN ADVANCE OF A
WARM/OCCLUDED FRONT JUST OFFSHORE. THE 12Z 4KM MM5 CAME IN MUCH
STRONGER AND WIDESPREAD WITH 40 KT WINDS ACROSS THE N INTERIOR. THE
HIGH END GALE WARNING FOR THAT AREA LOOKS GOOD THROUGH THIS EVENING.
GALES WILL ALSO DEVELOP ON THE COAST WHICH WILL EXTEND INTO SUN
MORNING WITH A SECOND BURST OF WINDS WITH THE SURFACE LOW. THE MM5
IS SHOWING WIDESPREAD 40 KT THERE AS WELL WHICH IS SHORT OF STORM
FORCE...SO I WILL MAINTAIN THE HIGH END GALE.
A POTENTIALLY STRONG 985-990 MB SURFACE LOW WILL ENTER THE COASTAL
WATERS AFTER 09Z TONIGHT AND TRACK INTO THE CENTRAL/S WA COAST
AROUND 12Z. WINDS BEHIND THE FRONT WILL RISE DRASTICALLY WITH HIGH
END GALES EXPECTED THROUGH SUN MORNING ACROSS THE COASTAL
WATERS...ESPECIALLY OVER THE SOUTH/CENTRAL PORTIONS. A 3-4 HOUR
BURST STRONG WLY WINDS DOWN THE STRAIT INTO THE WHIDBEY ISLAND AND
ADMIRALTY INLET AREA IS ALSO EXPECTED AFTER 12Z. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS REMAIN IN EFFECT FOR PORTIONS OF WESTERN
WASHINGTON...
WINTER STORM WARNING IN EFFECT FOR THE OLYMPIC MOUNTAINS TO 4
AM PST SUNDAY AND FOR THE CASCADES FROM TO 1 PM PST
SUNDAY...
HIGH WIND WARNING FOR THE CENTRAL AND SOUTH WASHINGTON
COAST...LOWER CHEHALIS VALLEY...SOUTHWEST INTERIOR...AND
ADMIRALTY INLET AREA THROUGH 10 AM SUNDAY...
HIGH WIND WARNING FOR THE NORTH INTERIOR OF WESTERN WASHINGTON
THROUGH MIDNIGHT TONIGHT...
WIND ADVISORY FOR THE CENTRAL PUGET SOUND AREA AND STRAIT OF
JUAN DE FUCA ZONES MIDNIGHT TONIGHT THROUGH SUNDAY MORNING...
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS...ADMIRALTY
INLET AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA THROUGH
SUNDAY MORNING.
.A GALE WARNING IS IN EFFECT FOR THE NORTHERN INLAND WATERS
THROUGH MIDNIGHT TONIGHT.
.A GALE WARNING IS IN EFFECT FOR THE CENTRAL STRAIT FROM LATE
TONIGHT THROUGH SUNDAY MORNING.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR PUGET SOUND THROUGH
SUNDAY MORNING.
$$
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000
FXUS66 KSEW 211915 AAA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1113 AM PST SAT NOV 21 2009
.SYNOPSIS...A WEAK UPPER LEVEL RIDGE WILL MOVE OVER WESTERN
WASHINGTON THROUGH MIDDAY TODAY...FOLLOWED QUICKLY BY A VIGOROUS
FRONTAL SYSTEM THIS AFTERNOON AND EVENING BRINGING RAIN AND WINDY
CONDITIONS TO THE AREA INTO SUNDAY. HEAVY SNOW WILL FALL IN THE
MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW 3000 FEET. A
WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND MONDAY
NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATER IN THE WEEK.
&&
.SHORT TERM...NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON AND
LINGERING SCATTERED SHOWERS ACROSS THE AREA THIS MORNING. THE
FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT. THE WEAK OFFSHORE RIDGE
WILL CONTINUE TO MOVE QUICKLY ACROSS WESTERN WASHINGTON THIS
MORNING...FOLLOWED BY THE SOUTH END OF AN OCCLUDED FRONT SWINGING
INTO BRITISH COLUMBIA BRINGING SIGNIFICANT PRECIPITATION TO THE THE
COAST AND OLYMPICS THIS AFTERNOON. A FRONTAL WAVE AND STRONG JET
WILL 45N/145W WILL DEEPEN AND MOVE THROUGH THE FORECAST AREA
TONIGHT.
HEAVY SNOW FOR THE MOUNTAINS REMAINS ON TRACK WITH IMPRESSIVE
PRECIPITATION AMOUNTS OVER THE OLYMPICS IN THE 3 TO 4 INCH RANGE AND
THE CASCADES IN THE 1 TO 3 INCH NEIGHBORHOOD THROUGH SUNDAY MORNING.
SNOW LEVELS RISE TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...
WITH ROUGHLY TO 30 TO 40 INCHES OF SNOW EXPECTED FOR THE OLYMPICS
AND 10 TO 30 INCHES FOR THE CASCADES. EVEN THE RELATIVELY DRIER
HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS.
THE TRACK OF THE SURFACE LOW REMAINS ONE OF THE FORECAST CHALANGES
FOR THE DAY. THE MOST LIKELY SCENARIO REMAINS THAT IT WILL REACH THE
CENTRAL WASHINGTON COAST AROUND MIDNIGHT TONIGHT...MOVE NORTHEAST
ACROSS THE OLYMPIC PENINSULA AND INTO THE NORTH PART OF THE PUGET
SOUND REGION TO AROUND MT BAKER AT 4 AM AND THEN HEAD INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS ACROSS THE
AREA. STONGEST WINDS WILL LIKELY BE WITH THE SOUTHERLIES AHEAD OF
THE LOW TONIGHT ESPECIALLY ALONG THE COAST AND NORTHWEST
INTERIOR...AND AGAIN WITH THE WESTERLIES SUNDAY MORNING THROUGH THE
EAST STRAIT INTO WHIDBEY ISLAND. FOR NOW HAVE ISSUED A HIGH WIND
WATCH FOR THE CENTRAL WASHINGTON COAST THROUGH THE CHEHALIS GAP AND
INTO THE SOUTHWEST INTERIOR FOR THE STRONG WESTERLIES WITH THE LOW
SUNDAY MORNING. IN ADDITION HAVE ISSUED A WIND ADVISORY FOR THE
NORTH INTERIOR...ADMIRALTY INLET...SAN JUANS AND EAST STRAIT FOR THE
SOUTHERLIES THIS AFTERNOON AND TONGITH FOLLOWED BY THE WESTERLIES
WITH AND BEHIND THE LOW. WILL BE WATCHING EVOLUTION AND TRACK OF THE
LOW AS IT APPROACHES THE COAST THIS AFTERNOON. WINDS SHOULD BEGIN TO
COME DOWN BY LATE SUNDAY MORNING ALL AREAS.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON EVENING AS AN
UPPER RIDGE WILL MOVE OVERHEAD SUNDAY EVENING. THE RIDGE KICKS EAST
QUICKLY MONDAY AHEAD OF ANOTHER FRONTAL SYSTEM. THIS SYSTEM COULD
STILL BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT WEAKENS AS IT MOVES INLAND MONDAY
NIGHT. COMPARED TO LAST SEVERAL SYSTEMS THIS WILL BE AN UNEVENTFUL
SYSTEM...MARKING THE BEGINNING OF A PERIOD OF QUIETER WEATHER. COOK
.LONG TERM...FROM PREVIOUS DISCUSSION...A WEAK UPPER RIDGE WILL
FOLLOW THE FRONT THAT MOVES THROUGH MONDAY AND MONDAY NIGHT. THERE
IS JUST A CHANCE OF RAIN IN THE FORECAST FOR TUESDAY AND
WEDNESDAY...WITH A FAIRLY GOOD CHANCE FOR SOME DRY WEATHER OVER
THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY MOVE ACROSS WESTERN
WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER FRONTAL WAVE WILL
PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND FRIDAY...THOUGH
DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY BY LATE IN THE
WEEK. MCDONNAL
&&
.HYDROLOGY...TODAYS SYSTEM WILL BRING IMPRESSIVE AMOUNTS OF
PRECIPITATION TO THE CASCADES AND OLYMPICS...BUT RELATIVELY LOW SNOW
LEVELS WILL MITIGATE THE IMPACT ON RIVERS EXCEPT THE TWO RIVERS THAT
ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND THE
LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. THE SNOW LEVEL
WILL ONLY RISING TO AROUND 3000 FT...MAKING THIS MOSTLY A MOUNTAIN
SNOW EVENT AND NOT A RAIN EVENT.
THE SKOKOMISH RIVER HAS FALLEN TO NEAR OR JUST BELOW FLOOD STAGE AT
THIS TIME...NEW FORECAST GUIDANCE SHOWS THE RIVER RISING AGAIN TO
JUST BELOW 17 FEET BY EARLY SUNDAY MORNING. IN ADDITION...THERE WILL
BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM #2 INTO THE NORTH
FORK SKOKOMISH RIVER THIS AFTERNOON. ACCORDINGLY WILL EXTEND THE
WARNING FOR THE SKOKOMISH INTO MONDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT REMAINS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY LOOKS TO BE PROGRESSIVE ENOUGH AND WEAK
ENOUGH TO BE OF LITTLE CONCERN WITH RESPECT TO FLOODING. THE AIR
MASS OVER THE NORTHWEST FOR THE REMAINDER OF THE WEEK WILL BE WARMER
WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE EXPECTED TO
AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED TO CAUSE
ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. COOK
&&
.AVIATION...A WARM FRONT WILL SPREAD RAIN INTO WRN WA THIS AFTERNOON
THROUGH TONIGHT. SW FLOW ALOFT WILL INCREASE THROUGH THE DAY AND
BECOME STRONG SLY FLOW BY THIS EVENING. THE ATMOSPHERE WILL REMAIN
MOIST AND STABLE.
A STRONG SURFACE LOW WILL DEVELOP OFFSHORE TODAY AND
TONIGHT...REACHING THE S OR CENTRAL WA COAST BY 12Z SUN MORNING AS A
POTENTIAL 985 MB LOW. THIS WILL BRING STRONG SLY FLOW ALOFT AND AT
THE SURFACE...SHIFTING WLY AFTER 12Z AS THE LOW TRACKS INLAND NEAR
KHQM...PROBABLY TRACKING JUST SOUTH OF KOLM. HOWEVER...THE TRACK IS
UNCERTAIN AT THIS TIME WITH SOME MODELS SHOWING A MORE NORTHERN
SOLUTION.
KSEA...SLY WINDS 8-15 KT TODAY...BECOMING MORE ELY TONIGHT. THERE
WILL BE A POTENTIAL FOR LLWS BETWEEN 03Z AND 12Z SUN DUE TO ELY
WINDS AT THE SFC AND STRONG SLY WINDS NEAR 2K FT. CONFIDENCE IS
STILL LOW BUT MAY WILL MONITOR AND IF NEEDED UPDATE THE TAF PRIOR TO
THE 00Z ISSUANCE. LATEST 12Z MODEL SOLUTIONS CONTINUE TO VARY
CONSIDERABLE REGARDING THE TRACK AND DEPTH OF A SURFACE LOW NOW
EXPECTED TO AFFECT THE AREA. WINDS WILL INCREASE DRAMATICALLY FROM
THE SW SOMETIME BETWEEN 12Z AND 15Z. CONCERNING CIGS...ANTICIPATE
CIGS TO GRADUALLY LOWER DURING THE DAY...ALTHOUGH THERE WILL BE
OCCASIONAL CIGS NEAR 2500 FT THIS MORNING. BY LATE THIS
EVENING...CIGS SHOULD BE NEAR 2K FT...WITH RAIN AND FOG REDUCING
VSBYS INTO THE 3-5SM RANGE. DTM
&&
.MARINE...WINDS WILL PICK UP ALONG THE COAST BY MIDDAY AND ACROSS
THE INLAND WATERS DURING THE AFTERNOON AS A WARM FRONT REACHES
WESTERN WASHINGTON. LATEST MODELS SHOW GALES TO DEVELOP WITH THIS
INITIAL FRONT FROM AROUND THE E ENTRANCE/ADMIRALTY INLET NWD AND
ALSO THE COASTAL WATERS. WIND ADVISORY FOR THE SOUND STILL LOOKS
GOOD.
A POTENTIALLY STRONG 985 MB SURFACE LOW WILL ENTER THE COASTAL
WATERS AFTER 09Z TONIGHT AND TRACK INTO THE CENTRAL/S WA COAST
AROUND 12Z. WINDS BEHIND THE FRONT WILL RISE DRASTICALLY SO I UPPED
THE WINDS TO HIGH END GALE AND EXTENDED THE WARNING THROUGH SUN
MORNING. DEPENDING ON THE EXACT TRACK...STORM FORCE WINDS COULD BE
POSSIBLE ACROSS THE CENTRAL/S WA COASTAL WATERS. WILL EVALUATE THIS
POSSIBILITY BEFORE THE AFTERNOON COASTAL FORECAST ISSUANCE. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR
A PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
WIND ADVISORY IN EFFECT FOR THE NORTH INTERIOR...EAST
STRAIT...AND ADMIRALTY INLET THROUGH SUNDAY MORNING.
HIGH WIND WATCH IN EFFECT FOR THE CENTRAL COAST...LOWER
CHEHALIS...AND SOUTHWEST INTERIOR FROM LATE TONIGHT THROUGH
SUNDAY MORNING...
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS...AND
FROM ADMIRALTY INLET NORTHWARD THROUGH EARLY SUN MORNING.
.A GALE WATCH IS IN EFFECT FOR THE CENTRAL AND
EAST STRAIT...AND ADMIRALTY INLET FROM EARLY
SUN MORNING THROUGH SUNDAY AFTERNOON.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR PUGET SOUND FROM
NOON THROUGH SUNDAY MORNING.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 211233 AAA
AFDSEW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
433 AM PST SAT NOV 21 2009
UPDATED THE AVIATION AND MARINE SEGMENTS.
.SYNOPSIS...A WEAK RIDGE WILL MOVE THROUGH WESTERN WASHINGTON THIS
MORNING...FOLLOWED QUICKLY BY A VIGOROUS FRONTAL SYSTEM. THIS SYSTEM
WILL BRING RAIN AND WINDY CONDITIONS TONIGHT AND SUNDAY. HEAVY SNOW
WILL FALL IN THE MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW
3000 FEET. A WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND
MONDAY NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATE IN THE WEEK.
&&
.SHORT TERM...WE HAVE NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON
BETWEEN AN UPPER TROUGH THAT MOVED THROUGH THE AREA OVERNIGHT AND A
WEAK UPPER RIDGE OFFSHORE ALONG 130W. THERE ARE STILL SCATTERED
SHOWERS ACROSS THE FORECAST AREA THIS MORNING...AND A PUGET SOUND
CONVERGENCE ZONE EXTENDING ACROSS ISLAND AND SNOHOMISH COUNTIES. IT
IS STILL BREEZY IN SOME AREAS...BUT THE WIND SHOULD EASE OVER THE
NEXT FEW HOURS AS THE SURFACE HIGH PRESSURE THAT HAS BEEN BUILDING
INTO THE AREA SHIFTS EAST OF THE CASCADES AHEAD OF THE NEXT FRONT.
THE FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT AND TEMPERATURES
ACROSS THE WESTERN WASHINGTON LOWLANDS WERE IN THE UPPER 30S TO MID
40S AT 3 AM.
THE WEAK RIDGE OFFSHORE WILL MOVE QUICKLY ACROSS WESTERN WASHINGTON
THIS MORNING...AND THE CONVERGENCE ZONE WILL LIKELY WEAKEN AND
DISSIPATE. THE SOUTH END OF AN OCCLUDED FRONT SWINGING INTO BRITISH
COLUMBIA WILL QUICKLY FOLLOW THE RIDGE...WITH SIGNIFICANT
PRECIPITATION REACHING THE COAST AND OLYMPICS THIS AFTERNOON. A
FRONTAL WAVE BEGINNING TO DEVELOP NEAR 45N/145W WILL DEEPEN AS IT
MOVES RAPIDLY EASTWARD WITH THE HELP OF A 140 KT JET. IT WILL MOVE
THROUGH THE FORECAST AREA TONIGHT.
HEAVY SNOW IN THE MOUNTAINS LOOKS LIKE A SURE BET. THE SNOW LEVEL
WILL RISE ONLY TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...AND
PRECIPITATION AMOUNTS WILL BE IMPRESSIVE. LIQUID AMOUNTS OF 3 TO 4
INCHES IN THE OLYMPICS ARE POSSIBLE THROUGH SUNDAY MORNING --
TRANSLATING ROUGHLY TO 30 TO 40 INCHES OF SNOW. EVEN THE RELATIVELY
DRIER HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS. WATER
EQUIVALENTS IN THE CASCADES WILL LIKELY BE IN THE 1 TO 3 INCH
RANGE...FOR SNOWFALL TOTALS OF 10 INCHES TO 2.5 FT. THE WINTER STORM
WATCH WILL BE UPGRADED TO A WARNING WITH THE EARLY MORNING FORECAST
PACKAGE.
ONE MATTER THAT IS SOMEWHAT UNCERTAIN IS THE TRACK OF THE SURFACE
LOW. THE MOST LIKELY SCENARIO IS THAT IT WILL REACH THE CENTRAL
WASHINGTON COAST AROUND MIDNIGHT TONIGHT...TRACK NORTHEAST ACROSS
THE OLYMPIC PENINSULA AND THE NORTH PART OF THE PUGET SOUND REGION
TO AROUND MT BAKER AT 4 AM...THEN HEAD RAPIDLY INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS...BUT THERE
APPEARS TO BE LITTLE THREAT OF A WIND STORM.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON AND EVENING...
AND AN UPPER RIDGE WILL MOVE INLAND SUNDAY NIGHT. THE RIDGE WILL
QUICKLY HEAD EAST OF THE CASCADES MONDAY AND ANOTHER FRONTAL SYSTEM
JUST UPSTREAM OF THE RIDGE WILL ARRIVE. THIS SYSTEM COULD INITIALLY
BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT IT WILL WEAKEN AS IT MOVES INLAND
MONDAY NIGHT. BY RECENT STANDARDS THIS WILL BE AN UNEVENTFUL SYSTEM
AND IT WILL MARK THE BEGINNING OF A PERIOD OF QUIETER...THOUGH NOT
NECESSARILY DRY...WEATHER. MCDONNAL
.LONG TERM...A WEAK UPPER RIDGE WILL FOLLOW THE FRONT THAT MOVES
THROUGH MONDAY AND MONDAY NIGHT. THERE IS JUST A CHANCE OF RAIN IN
THE FORECAST FOR TUESDAY AND WEDNESDAY...WITH A FAIRLY GOOD CHANCE
FOR SOME DRY WEATHER OVER THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY
MOVE ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER
FRONTAL WAVE WILL PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND
FRIDAY...THOUGH DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY
BY LATE IN THE WEEK. MCDONNAL
&&
.HYDROLOGY...THE SYSTEM COMING IN TODAY THROUGH MIDDAY SUNDAY ...
WHILE IT WILL PRODUCE IMPRESSIVE AMOUNTS OF PRECIPITATION...WILL
HAVE MINIMAL EFFECT ON RIVERS EXCEPT POSSIBLY FOR THE TWO RIVERS
THAT ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND
THE LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. WITH THE
SNOW LEVEL ONLY RISING TO AROUND 3000 FT...IT WILL BE A MOUNTAIN
SNOW PRODUCER NOT A FLOODING RAIN PRODUCER.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
TODAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM
#2 INTO THE NORTH FORK SKOKOMISH RIVER TODAY. THIS RELEASE WILL KEEP
THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR THE RIVER
TO REMAIN JUST BELOW FLOOD STAGE TONIGHT AND SUNDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT IS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. MCDONNAL
&&
.AVIATION...A WEAK...UPPER RIDGE OVER THE REGION WILL MOVE E
TONIGHT...ALLOWING A STRONG...UPPER TROF TO MOVE OVER THE AREA.
INCREASING WLY FLOW ALOFT...SUBSIDING AND BECOMING NW LATE TONIGHT.
AT THE SFC...A FRONTAL SYSTEM OVER THE ERN PAC WILL RAPIDLY APPROACH
WRN WA DURING THE DAY TODAY...RESULTING IN INCREASED SLY WINDS. THE
OCCLUDED FRONT WILL MOVE ACROSS THE AREA THIS EVENING. A SECONDARY
SFC LOW IS ANTICIPATED TO DEVELOP OFF THE FAR SW WA OR FAR NW OREGON
COAST THIS EVENING...AND TRACK NEWD ACROSS THE AREA LATER TONIGHT.
THUS EXPECT THE WINDS TO BACK BEHIND THE OCCLUDED FRONT THIS
EVENING...AND THIS SHOULD RAISE THE POTENTIAL FOR LLWS SINCE WINDS
ABOVE THE SFC WILL REMAIN SLY. WINDS WILL PICK UP DRAMATICALLY FROM
THE W OR SW LATE TONIGHT OR EARLY SUNDAY ONCE THE SFC LOW MOVES E OF
THE AREA.
MEANWHILE...A PUGET SOUND CONVERGENCE ZONE /PSCZ/ WAS ROUGHLY
LOCATED BETWEEN KPAE AND KAWO AT THIS TIME. THIS FEATURE SHOULD
DRIFT N AND DISSIPATE BY MIDMORNING AS ITS SUPPORT WANES.
KSEA...WINDS WILL REMAIN SLY TODAY...BECOMING MORE ELY TONIGHT.
THERE WILL BE A POTENTIAL FOR LLWS BETWEEN 0000 AND 1200 UTC SUNDAY
DUE TO ELY WINDS AT THE SFC AND STRONG SLY WINDS NEAR 2K FT. HAVE
HELD OFF ON MENTIONING THIS IN THE TAF TIL WE SEE ANOTHER MODEL RUN.
THE CURRENT MODEL SOLUTIONS WERE QUITE DIFFERENT THAN THE PREVIOUS
RUN DUE TO A MORE VIGOROUS SYSTEM NOW EXPECTED TO AFFECT THE AREA.
WINDS WILL INCREASE DRAMATICALLY FROM THE SW SOMETIME BETWEEN 1000
UTC AND 1200 UTC SUNDAY. CONCERNING CIGS...ANTICIPATE CIGS TO
GRADUALLY LOWER DURING THE DAY...ALTHOUGH THERE WILL BE OCCASIONAL
CIGS NEAR 2500 FT THIS MORNING. BY LATE THIS EVENING...CIGS SHOULD
BE NEAR 2K FT...WITH RAIN AND FOG REDUCING VSBYS INTO THE 3-5SM
RANGE.
&&
.MARINE...THERE WAS A SIGNIFICANT CHANGE IN THE FORECAST FROM THE
PREVIOUS ONE DUE TO A MORE VIGOROUS SYSTEM EXPECTED TO AFFECT THE
AREA TODAY. SLY WINDS ARE STILL ANTICIPATED TO INCREASE DURING THE
DAY...AHEAD OF A FAST-MOVING FRONTAL SYSTEM STILL WELL OFFSHORE...
FOR GALE OR SMALL CRAFT ADVISORY WIND SPEEDS. THE OCCLUDED FRONT
WILL SWEEP ACROSS THE AREA THIS EVENING. DUE TO SOMEWHAT LOW
CONFIDENCE HAVE WENT WITH A SMALL CRAFT ADVISORY FOR THE NORTHERN
INLAND WATERS AND EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA TODAY
INSTEAD OF UPGRADING THE PREVIOUS GALE WATCH TO A WARNING.
ANOTHER SURFACE WAVE OR LOW IS EXPECTED TO DEVELOP OFF THE FAR SW
WASHINGTON OR FAR NW OREGON COAST TONIGHT...AND THIS WILL CAUSE THE
WINDS TO BACK AND DROP OFF...ESPECIALLY ACROSS THE INLAND WATERS.
THE LOW WILL MOVE NE ACROSS INTERIOR WESTERN WASHINGTON OVERNIGHT.
WINDS WILL KICK BACK UP LATE TONIGHT OR EARLY SUNDAY IN RESPONSE TO
STRONG ONSHORE OR WESTERLY FLOW DEVELOPING. CONFIDENCE WAS FAIRLY
HIGH THAT GALE FORCE WINDS WILL DEVELOP OVER THE STRAIT OF JUAN DE
FUCA EARLY SUNDAY...THUS HAVE ISSUED A GALE WATCH FOR THE CENTRAL
AND EASTERN STRAIT. THERE IS A POSSIBILITY THAT WINDS MAY BRIEFLY
REACH STORM FORCE...NEAR 50 KNOTS...OVER THE CENTRAL STRAIT SUNDAY
MORNING WITH THE INITIAL PUSH.
ANTICIPATE THE ONSHORE FLOW TO WEAKEN AND BECOME SOUTHERLY SUNDAY
NIGHT. THE NEXT FRONTAL SYSTEM WILL AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR A
PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THROUGH THIS
EVENING.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING
WATERS.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT TIL NOON MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 211212
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PDT SAT NOV 21 2009
.SYNOPSIS...A WEAK RIDGE WILL MOVE THROUGH WESTERN WASHINGTON THIS
MORNING...FOLLOWED QUICKLY BY A VIGOROUS FRONTAL SYSTEM. THIS SYSTEM
WILL BRING RAIN AND WINDY CONDITIONS TONIGHT AND SUNDAY. HEAVY SNOW
WILL FALL IN THE MOUNTAINS WITH THE SNOW LEVEL REMAINING AT OR BELOW
3000 FEET. A WEAKER FRONT WILL MOVE THROUGH THE AREA MONDAY AND
MONDAY NIGHT...AND ANOTHER WEAK FRONT WILL ARRIVE LATE IN THE WEEK.
&&
.SHORT TERM...WE HAVE NORTHWEST FLOW ALOFT OVER WESTERN WASHINGTON
BETWEEN AN UPPER TROUGH THAT MOVED THROUGH THE AREA OVERNIGHT AND A
WEAK UPPER RIDGE OFFSHORE ALONG 130W. THERE ARE STILL SCATTERED
SHOWERS ACROSS THE FORECAST AREA THIS MORNING...AND A PUGET SOUND
CONVERGENCE ZONE EXTENDING ACROSS ISLAND AND SNOHOMISH COUNTIES. IT
IS STILL BREEZY IN SOME AREAS...BUT THE WIND SHOULD EASE OVER THE
NEXT FEW HOURS AS THE SURFACE HIGH PRESSURE THAT HAS BEEN BUILDING
INTO THE AREA SHIFTS EAST OF THE CASCADES AHEAD OF THE NEXT FRONT.
THE FREEZING LEVEL HAS FALLEN TO AROUND 3000 FT AND TEMPERATURES
ACROSS THE WESTERN WASHINGTON LOWLANDS WERE IN THE UPPER 30S TO MID
40S AT 3 AM.
THE WEAK RIDGE OFFSHORE WILL MOVE QUICKLY ACROSS WESTERN WASHINGTON
THIS MORNING...AND THE CONVERGENCE ZONE WILL LIKELY WEAKEN AND
DISSIPATE. THE SOUTH END OF AN OCCLUDED FRONT SWINGING INTO BRITISH
COLUMBIA WILL QUICKLY FOLLOW THE RIDGE...WITH SIGNIFICANT
PRECIPITATION REACHING THE COAST AND OLYMPICS THIS AFTERNOON. A
FRONTAL WAVE BEGINNING TO DEVELOP NEAR 45N/145W WILL DEEPEN AS IT
MOVES RAPIDLY EASTWARD WITH THE HELP OF A 140 KT JET. IT WILL MOVE
THROUGH THE FORECAST AREA TONIGHT.
HEAVY SNOW IN THE MOUNTAINS LOOKS LIKE A SURE BET. THE SNOW LEVEL
WILL RISE ONLY TO AROUND 3000 FT AS THIS FEATURE MOVES THROUGH...AND
PRECIPITATION AMOUNTS WILL BE IMPRESSIVE. LIQUID AMOUNTS OF 3 TO 4
INCHES IN THE OLYMPICS ARE POSSIBLE THROUGH SUNDAY MORNING --
TRANSLATING ROUGHLY TO 30 TO 40 INCHES OF SNOW. EVEN THE RELATIVELY
DRIER HURRICANE RIDGE AREA SHOULD RECEIVE WINTER STORM WARNING
AMOUNTS...IE 12 INCHES IN 12 HOURS OR 18 INCHES IN 24 HOURS. WATER
EQUIVALENTS IN THE CASCADES WILL LIKELY BE IN THE 1 TO 3 INCH
RANGE...FOR SNOWFALL TOTALS OF 10 INCHES TO 2.5 FT. THE WINTER STORM
WATCH WILL BE UPGRADED TO A WARNING WITH THE EARLY MORNING FORECAST
PACKAGE.
ONE MATTER THAT IS SOMEWHAT UNCERTAIN IS THE TRACK OF THE SURFACE
LOW. THE MOST LIKELY SCENARIO IS THAT IT WILL REACH THE CENTRAL
WASHINGTON COAST AROUND MIDNIGHT TONIGHT...TRACK NORTHEAST ACROSS
THE OLYMPIC PENINSULA AND THE NORTH PART OF THE PUGET SOUND REGION
TO AROUND MT BAKER AT 4 AM...THEN HEAD RAPIDLY INTO BRITISH
COLUMBIA. IT WILL PRODUCE BREEZY TO WINDY CONDITIONS...BUT THERE
APPEARS TO BE LITTLE THREAT OF A WIND STORM.
POST-FRONTAL SHOWERS WILL TAPER OFF SUNDAY AFTERNOON AND EVENING...
AND AN UPPER RIDGE WILL MOVE INLAND SUNDAY NIGHT. THE RIDGE WILL
QUICKLY HEAD EAST OF THE CASCADES MONDAY AND ANOTHER FRONTAL SYSTEM
JUST UPSTREAM OF THE RIDGE WILL ARRIVE. THIS SYSTEM COULD INITIALLY
BRING DECENT PRECIPITATION AMOUNTS TO THE COAST AND OLYMPIC
PENINSULA MONDAY AFTERNOON...BUT IT WILL WEAKEN AS IT MOVES INLAND
MONDAY NIGHT. BY RECENT STANDARDS THIS WILL BE AN UNEVENTFUL SYSTEM
AND IT WILL MARK THE BEGINNING OF A PERIOD OF QUIETER...THOUGH NOT
NECESSARILY DRY...WEATHER. MCDONNAL
.LONG TERM...A WEAK UPPER RIDGE WILL FOLLOW THE FRONT THAT MOVES
THROUGH MONDAY AND MONDAY NIGHT. THERE IS JUST A CHANCE OF RAIN IN
THE FORECAST FOR TUESDAY AND WEDNESDAY...WITH A FAIRLY GOOD CHANCE
FOR SOME DRY WEATHER OVER THOSE TWO DAYS. A WEAK FRONT WILL SLOWLY
MOVE ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT AND THURSDAY. ANOTHER
FRONTAL WAVE WILL PROBABLY KEEP THE AREA WET THURSDAY NIGHT AND
FRIDAY...THOUGH DISAGREEMENT BETWEEN MODELS DROPS OFF CONSIDERABLY
BY LATE IN THE WEEK. MCDONNAL
&&
.HYDROLOGY...THE SYSTEM COMING IN TODAY THROUGH MIDDAY SUNDAY ...
WHILE IT WILL PRODUCE IMPRESSIVE AMOUNTS OF PRECIPITATION...WILL
HAVE MINIMAL EFFECT ON RIVERS EXCEPT POSSIBLY FOR THE TWO RIVERS
THAT ARE ALREADY CLOSE TO OR ABOVE FLOOD STAGE -- THE SKOKOMISH AND
THE LOWER REACH OF THE CHEHALIS IN GRAYS HARBOR COUNTY. WITH THE
SNOW LEVEL ONLY RISING TO AROUND 3000 FT...IT WILL BE A MOUNTAIN
SNOW PRODUCER NOT A FLOODING RAIN PRODUCER.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
TODAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN DAM
#2 INTO THE NORTH FORK SKOKOMISH RIVER TODAY. THIS RELEASE WILL KEEP
THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR THE RIVER
TO REMAIN JUST BELOW FLOOD STAGE TONIGHT AND SUNDAY.
A FLOOD WATCH REMAINS IN EFFECT FOR THE LOWER REACH OF THE CHEHALIS
RIVER IN GRAYS HARBOR COUNTY...WHICH HAS BEEN WITHIN A FOOT OF FLOOD
STAGE FOR THE PAST TWO DAYS. IT IS CONCEIVABLE THAT THE
PRECIPITATION FROM THE INCOMING SYSTEM COULD HELP FINALLY NUDGE THE
LOWER CHEHALIS ABOVE FLOOD STAGE. IF FLOODING DOES OCCUR IT WILL BE
MINOR.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. MCDONNAL
&&
.AVIATION...DELAYED.
&&
.MARINE...A STRONG FRONTAL SYSTEM WILL APPROACH THE AREA TODAY...
RESULTING IN INCREASED SOUTHERLY FLOW. THE OCCLUDED FRONT WILL THEN
MOVE ACROSS THE AREA THIS EVENING. STRONG ONSHORE OR WESTERLY FLOW
WILL DEVELOP ON SUNDAY IN THE WAKE OF THIS FRONT. EXPECT THE NEXT
FRONTAL SYSTEM TO AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES REMAIN IN EFFECT FOR A
PORTION OF THE CWA.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES FROM THIS AFTERNOON THROUGH SUNDAY MORNING.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THROUGH THIS
EVENING.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING
WATERS.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT TIL NOON MON.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 210515
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PST FRI NOV 20 2009
.SYNOPSIS...A TROUGH WILL MOVE THROUGH WESTERN WASHINGTON THIS
EVENING. A DEVELOPING SURFACE LOW IN THE EAST CENTRAL PACIFIC WILL
MOVE ACROSS SOUTHERN PORTIONS OF WASHINGTON SUNDAY NIGHT. A FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA MONDAY OR MONDAY NIGHT. YET
ANOTHER FRONT WILL MOVE ACROSS THE AREA MIDWEEK.
&&
.SHORT TERM...A RATHER STRONG ZONAL FLOW CONTINUES ACROSS THE
PACIFIC THIS EVENING. BUT THE PATTERN ACROSS NORTH AMERICA IS
INCREASINGLY SPLIT. SO WHILE INCOMING SYSTEMS OVER THE NEXT SEVERAL
DAYS WILL NOT LIKELY BE AS STRONG OR AS WET AS SYSTEMS THAT IMPACTED
THE AREA DURING THE LAST WEEK...THE TIMING AND PLACEMENT OF SYSTEMS
WILL BE INCREASINGLY DIFFICULT FOR NUMERICAL MODELS TO HANDLE AS
TIME MOVES FORWARD.
THIS EVENING A COLD UPPER TROUGH IS MOVING ACROSS THE AREA WITH 500
MB TEMPERATURES AROUND -33C AND 850 MB TEMPERATURES AROUND -3C. THE
AIR MASS IS RATHER UNSTABLE...BUT WITH ABUNDANT MOISTURE ALOFT THE
CAPE IS ONLY AROUND 300J/KG AND THE CAPE PROFILE IS SKINNY. AS THE
CENTER OF THE UPPER TROUGH MOVED ACROSS THE AREA AROUND 5 PM...QUITE
A FEW THUNDERSTORMS DEVELOPED ACROSS THE NORTHERN INLAND WATERS.
THESE HAVE SINCE DIED OUT AS THEY MOVED INTO THE CANADIAN COASTAL
RANGE. EARLIER...PRES GRADIENTS WERE STRONGLY SOUTHERLY AND NEAR
GALE FORCE SLY WINDS DEVELOPED ACROSS THE INLAND WATERS. NOW THAT
STRONG INFLOW HAS DEVELOPED IN THE STRAIT OF JUAN DE FUCA...THE SW
WINDS OVER THE INLAND VALLEYS WILL GRADUALLY DIE DOWN. AN AREA OF
CONVERGENCE IS CENTERED OVER SKAGIT COUNTY THIS EVENING. AS THE
UPPER TROUGH MOVES EAST AND FLOW BECOMES MORE WESTERLY AND RELAXES
SOMEWHAT...EXPECT A PUGET SOUND CONVERGENCE ZONE TO SET UP AROUND
THE EVERETT AREA AND CONTINUE NORTH OF THE SEATTLE AREA OVERNIGHT
BEFORE DISSIPATING. SNOW LEVELS IN THE MOUNTAINS SHOULD AVERAGE
AROUND 2000 FT AND HIGH END ADVISORY AMOUNTS OF SNOW ARE POSSIBLE IN
THE NORTH CASCADES NORTH OF STEVENS PASS IN SNOHOMISH AND SKAGIT
COUNTIES.
A DEVELOPING FRONTAL SYSTEM IS SEEN AHEAD OF A LEADING EDGE OF A 140
KT JET STREAK NEAR 44N/159W. THE 00Z NAM AND GFS SOLUTIONS ARE IN
AGREEMENT WITH THEIR 18Z RUNS IN DEVELOPING THIS WAVE TO ABOUT 990
MB AND SLAMMING IT INTO THE PAC NW SOMEWHERE BETWEEN THE MOUNT OF
THE COLUMBIA RIVER...NAM12...AND THE CHEHALIS GAP BEFORE TAKING IT
NE INTO THE CENTRAL TO NORTH CASCADES SAT NIGHT. MODERATELY STRONG
WINDS WITH MARINE GALES WILL ACCOMPANY THIS LOW...BUT WIND SPEEDS
AND DIRECTIONS WILL BE QUITE DEPENDENT ON THE UNCERTAIN TRACK OF
THIS FAST MOVING LOW. IF THERE WERE ANY COOL AIR AROUND OR HIGHER
PRES N AND EAST OF THE AREA...WE WOULD NEED TO WATCH OUT FOR LOWLAND
SNOW IN ADVANCE OF AND TO THE NORTH OF THE TRACK OF THE LOW WITH WET
BULB COOLING IN THE DEFORMATION ZONE TO THE NORTH. HOWEVER...ALL
MODELS SHOW TEMPERATURES BETWEEN 2000 FT AND THE SURFACE TO BE 2-4
DEG C TOO WARM...WHICH IS CONSISTENT WITH THE MARINE AIR MASS IN
PLACE AND THE SOMEWHAT SPLIT NATURE OF THIS NEXT INCOMING SYSTEM.
1.0 TO 1.5 INCHES OF PRECIPITATION ARE SEEN TO THE NORTH OF THE
TRACK OF THE LOW SAT NIGHT. WITH SNOW LEVELS AROUND 2000 FT AND
PRECIPITATION AMOUNTS OF THIS DEGREE...WILL ISSUE A WINTER STORM
WATCH FOR ALL OF THE MOUNTAINS SAT NIGHT THROUGH MIDDAY SUN.
CONDITIONS BRIEFLY DRY LATER SUN AFTERNOON INTO SUN NIGHT BETWEEN
SUN MORNINGS DEPARTING LOW AND THE NEXT FRONTAL SYSTEM THAT MOVES IN
MON OR MON NIGHT.
WILL UPDATE THE ZONES TO REFINE THE SHORT TERM AND TO ADD THE WINTER
STORM WATCH FOR THE MOUNTAINS SAT NIGHT THROUGH MIDDAY SUN. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...A WARM FRONT
MOVES THRU WRN WA MONDAY...AT 700MB THE TEMP WARMS FROM -14C LATE
SUN TO ARND -5C MON AFTERNOON. THE SURFACE PRES PATTERN IS RATHER
LACKLUSTER WITH THIS FRONT ON MONDAY...THE NAM SHOWS A FAIRLY DECENT
SE GRADIENT MONDAY MORNING BUT THEN BY MONDAY EVENING THE FRONT IS
DISSIPATING AND PRES IS RISING WITH LIGHT GRADIENTS AS 500MB HEIGHTS
RISE INTO THE LOWER 560S. THERE IS A GOOD CHANCE OF SOME DRY WEATHER
TUE AS THAT RIDGE BUILDS IN...THEN A FNTL BAND MOVES THRU WED OR
THU...OR BOTH. THE LATEST GFS SUGGESTS THE REMNANTS OF A WEAKENING
FNTL BAND FOR WED AND THEN A STRONGER SYS THU. THERE IS PRETTY GOOD
AGREEMENT THAT THE FIRST HALF OF THE WEEK WILL SEE A FAIRLY HIGH
FREEZING LEVEL BUT NOT MUCH PRECIP...AND THEN A LOWERING SNOW LEVEL
LATE IN THE WEEK WITH THE BEST GUESS FOR A DECENT COLD FROPA THU
NIGHT...SO FRIDAY COULD BE POSTFRONTAL AND COOL SHOWERY BUT I
HAVEN`T GONE FOR THAT MUCH DETAIL FOR A DAY SEVEN FCST THO I DID
SHOW THE SNOW LEVEL BACK BELOW THE PASSES BY FRIDAY FOR BETTER
SKIING LIKELY TOWARD THE END OF NEXT WEEK. 19
&&
.HYDROLOGY...PRECIPITATION HAS BECOME SHOWERY. WHILE 0.5-1.0 INCHES
OF PRECIPITATION ARE LIKELY IN THE NORTH CASCADES TONIGHT AND EARLY
SATURDAY...SNOW LEVELS WILL BE AROUND 2000 FT AND AFFECTS ON THE
RIVERS SHOULD BE MINIMAL.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
SATURDAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN
DAM #2 INTO THE NORTH FORK SKOKOMISH RIVER ON SATURDAY. THIS RELEASE
WILL KEEP THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR
THE RIVER TO REMAIN JUST BELOW FLOOD STAGE SATURDAY NIGHT AND SUNDAY.
THE SATSOP RIVER AT SATSOP HAS JUST FALLEN BELOW FLOOD STAGE AROUND
730 PM THIS EVENING. WILL LIKELY TAKE THE FLOOD WARNING FOR THE
SATSOP DOWN BY 10 PM.
THE LOWEST REACH OF THE CHEHALIS WILL BOUNCE AROUND AT A FOOT OR
LESS BELOW FLOOD STAGE THROUGH SATURDAY. MORE RAIN SATURDAY NIGHT
COULD KEEP THE THE LOWER CHEHALIS NEAR FLOOD STAGE. WILL MAINTAIN
THE FLOOD WATCH FOR THE CHEHALIS THROUGH SUNDAY FOR NOW. IF FLOODING
DOES OCCUR IT SHOULD BE MINOR.
ANOTHER SYSTEM WILL ARRIVE SATURDAY NIGHT INTO SUNDAY MORNING WITH
SIGNIFICANT PRECIPITATION IN THE MOUNTAINS. SNOW LEVELS WILL REMAIN
LOW THROUGH SUNDAY...AROUND 2000 FT...SO RENEWED FLOODING IS NOT
EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER.
ALBRECHT/BURKE
&&
.AVIATION...AN UPPER TROF OVER WRN WA WILL CONTINUE MOVING E. BY
EARLY SATURDAY...THIS SYSTEM WILL BE OVER THE GREAT BASIN. A
WEAK...UPPER RIDGE WILL FOLLOW ON THE HEELS OF THE UPPER TROF.
CONTINUED WLY FLOW ALOFT. THE AIR MASS WILL REMAIN MOIST. SLIGHTLY
UNSTABLE ATMOSPHERE OVER THE AREA WILL BECOME STABLE OVERNIGHT.
AT THE SFC...STRONG ONSHORE FLOW WILL WEAKEN OVERNIGHT. ANOTHER
FRONTAL SYSTEM WILL APPROACH THE REGION DURING THE DAY SATURDAY FOR
INCREASED SLY FLOW. CIGS WILL GENERALLY BE IN THE 4-8K FT RANGE...
ALTHOUGH EXPECT AREAS OF CIGS NEAR 2K FT. THERE MAY BE SOME PATCHY
FOG...REDUCING VSBYS DOWN TO 3SM...LATER TONIGHT OR EARLY SATURDAY
MORNING OVER THE SW INTERIOR IF THERE IS SUFFICIENT CLEARING.
CONCERNING THE PUGET SOUND CONVERGENCE ZONE /PSCZ/...IT APPEARED
THAT THE PSCZ WAS DEVELOPING OVER ITS FAVORED POSITION...JUST N OF
THE KING/SNOHOMISH COUNTY BORDER WHERE IT WILL REMAIN STATIONARY.
WOULD NOT RULE OUT AN ISOLATED LIGHTNING STRIKE WITHIN THE PSCZ TIL
MIDNIGHT. THE PSCZ WILL DISSIPATE LATE TONIGHT AS THE FLOW BECOMES
UNFAVORABLE FOR MAINTAINING IT.
KSEA...CIGS WILL GENERALLY BE IN THE 5-8K FT RANGE OVERNIGHT BUT
EXPECT OCCASIONAL CIGS NEAR 2500 FT. SLY WINDS WILL DIMINISH
OVERNIGHT.
&&
.MARINE...STRONG WESTERLY FLOW WILL WEAKEN AND BECOME SOUTHERLY
OVERNIGHT. A FRONTAL SYSTEM WILL APPROACH THE AREA DURING THE DAY
SATURDAY... RESULTING IN INCREASED SOUTHERLY FLOW. THE COLD OR
OCCLUDED FRONT IS EXPECTED TO MOVE ACROSS THE AREA SATURDAY NIGHT.
ONSHORE FLOW WILL CONTINUE ON SUNDAY BETWEEN SYSTEMS. THE NEXT
FRONTAL SYSTEM WILL AFFECT THE WATERS ON MON.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR
A PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES
TONIGHT.
.A WINTER STORM WATCH IS IN EFFECT FOR SATURDAY NIGHT THROUGH
MIDDAY SUNDAY IN THE OLYMPICS AND NORTH AND CENTRAL CASCADES
AND PASSES.
PZ...A GALE WARNING REMAINS IN EFFECT FOR THE CENTRAL AND
EASTERN STRAIT OF JUAN DE FUCA TIL MIDNIGHT.
.GALE WARNINGS ARE IN EFFECT FOR THE COASTAL WATERS AND
WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA SATURDAY
THROUGH SATURDAY EVENING.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE PUGET SOUND
AND HOOD CANAL TIL 4 AM SATURDAY.
.A GALE WATCH IS IN EFFECT FOR THE NORTHERN INLAND WATERS
FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING.
.A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR
CONDITIONS IS IN EFFECT TIL 10 AM SUNDAY.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
000
FXUS66 KSEW 202323
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PST FRI NOV 20 2009
.SYNOPSIS...A TROUGH WILL MOVE THROUGH WESTERN WASHINGTON THIS
EVENING. A FRONTAL SYSTEM WILL MOVE THROUGH WESTERN WASHINGTON
SATURDAY AFTERNOON AND NIGHT. A WARM FRONT WILL REACH THE AREA
MONDAY. A RIDGE WILL BUILD OVER THE REGION TUESDAY. A FRONTAL SYSTEM
WILL MOVE SLOWLY THROUGH THE AREA LATER WEDNESDAY AND THURSDAY.
&&
.SHORT TERM...SFC AND UPPER TROF WILL MOVE THRU WRN WA THIS
EVENING...BLUSTERY ON THE COAST AS THE SFC TROF MOVED THRU THIS
AFTERNOON. BREEZY THIS EVENING IN THE INTERIOR AS WELL AS SFC PRES
GRADIENTS INCREASE AS THE TROF MOVES INLAND AND FILLS...AT 3PM
OLM-BLI GRADIENT HAD JUMPED TO +3.3MB AND THAT GRADIENT SHUD PEAK AT
+4.5 LATE THIS AFTERNOON...WINDY FOR A FEW HOURS TIL THE PSCZ SETS
UP AND WINDS WILL DECREASE...ESPECIALLY NORTH OF SEATTLE IN THE
PSCZ. WLY WINDS DVLPG AND INCREASING IN THE STRAIT W/ A WLY GALE IN
THE FCST TO AID THAT PSCZ. COOLER AIR ALOFT WILL DESTABILIZE THE AIR
MASS AND SHOWERS WILL MOVE THRU WRN WA...BECMG INCREASINGLY
OROGRAPHIC OVERNIGHT WITH A GOOD CHANCE OF A PSCZ SETTING UP. WINTER
WEATHER ADVISORY IN THE CASCADES...IF THE PSCZ SETS UP MIGHT SEE A
FOOT OF NEW SNOW FROM PILCHUCK TO INDEX AND UP TOWARD STEVENS PASS
OVERNIGHT. SNOW LEVEL DROPS FM 2500 TO 1500FT...XCP MIGHT BE ARND
1000FT BY MIDNIGHT IN THE PSCZ OVR THE CASCADES AS 700MB TEMP COOLS
TO -15C. A BIT OF A BREAK SATURDAY MORNING ALTHOUGH THE NAM KEEPS IT
PRETTY DRIPPY SO HAVE HIGHER POPS THAN I WOULD NORMALLY SHOW AHEAD
OF THE NEXT FRONT. THAT NEXT FRONTAL SYS AND SFC LOW PRES CENTERS IN
THE 18Z NAM ARE A MUCH BETTER MATCH TO THE GLOBAL MODELS. A FIRST
LOW CENTER WITH THE OCFNT REACHES NRN VANCOUVER ISLAND SATURDAY
EVENING...THE FRONT EXTENDS SOUTH ALONG THE WA AND ORE COAST...AND
THEN THE NAM SPINS UP A SECONDARY LOW TO 988MB WHICH REACHES THE NRN
OREGON COAST AFTER MIDNIGHT...WITH A TRACK THRU NW ORE BY DAYBREAK
SUN. THIS SYSTEM WILL BE COOLER THAN PREVIOUS SYSTEMS BUT LOW LEVEL
THICKNESS VALUES DO NOT SUPPORT TAKING THE SNOW LEVEL FCST MUCH BLO
1500FT. THE 18Z GFS IS A NOTCH FURTHER NORTH WITH THE SFC LOW PRES
TRACK WITH A 995MB CENTER REACHING LONG BEACH OR GRAYS HARBOR BY
10PM SAT...IT WILL BE WORTH TAKING A CLOSE LOOK AT THE 00Z MESOSCALE
MODELS...THE GFS TRACK COULD BE WINDY IF IT IS SIMILAR TO THE 18Z
RUN...AND THE MESO MODELS ARE OFTEN A NOTCH DEEPER. IN ANY EVENT
WITH BREEZY SOLUTIONS THERE WILL BE ENUF ONSHORE FLOW TO ENSURE THE
SNOW LEVEL DOESN`T DROP BLO MUCH 1500FT LATE SAT NITE. 19
.LONG TERM...A WARM FRONT MOVES THRU WRN WA MONDAY...AT 700MB THE
TEMP WARMS FROM -14C LATE SUN TO ARND -5C MON AFTERNOON. THE SURFACE
PRES PATTERN IS RATHER LACKLUSTER WITH THIS FRONT ON MONDAY...THE
NAM SHOWS A FAIRLY DECENT SE GRADIENT MONDAY MORNING BUT THEN BY
MONDAY EVENING THE FRONT IS DISSIPATING AND PRES IS RISING WITH
LIGHT GRADIENTS AS 500MB HEIGHTS RISE INTO THE LOWER 560S. THERE IS
A GOOD CHANCE OF SOME DRY WEATHER TUE AS THAT RIDGE BUILDS IN...THEN
A FNTL BAND MOVES THRU WED OR THU...OR BOTH. THE LATEST GFS SUGGESTS
THE REMNANTS OF A WEAKENING FNTL BAND FOR WED AND THEN A STRONGER
SYS THU. THERE IS PRETTY GOOD AGREEMENT THAT THE FIRST HALF OF THE
WEEK WILL SEE A FAIRLY HIGH FREEZING LEVEL BUT NOT MUCH PRECIP...AND
THEN A LOWERING SNOW LEVEL LATE IN THE WEEK WITH THE BEST GUESS FOR
A DECENT COLD FROPA THU NIGHT...SO FRIDAY COULD BE POSTFRONTAL AND
COOL SHOWERY BUT I HAVEN`T GONE FOR THAT MUCH DETAIL FOR A DAY SEVEN
FCST THO I DID SHOW THE SNOW LEVEL BACK BELOW THE PASSES BY FRIDAY
FOR BETTER SKIING LIKELY TOWARD THE END OF NEXT WEEK. 19
&&
.HYDROLOGY...IN THE OLYMPICS ALL THAT REMAINS IS FOR THE HEAVY RAIN
FROM LAST NIGHT TO DRAIN TO THE OCEAN. ALL RIVERS ARE FALLING AND
ONLY TWO ARE ABOVE FLOOD STAGE...THE SATSOP AND SKOKOMISH. ALLOWED
THE AREAL FLOOD WARNING FOR JEFFERSON AND CLALLAM COUNTIES TO EXPIRE
AT 230 PM.
THE SKOKOMISH RIVER IS FORECAST TO FALL BELOW FLOOD STAGE ABOUT NOON
SATURDAY. THERE WILL BE A PLANNED RELEASE OF 3000 CFS FROM CUSHMAN
DAM #2 INTO THE NORTH FORK SKOKOMISH RIVER ON SATURDAY. THIS RELEASE
WILL KEEP THE SKOKOMISH RIVER RUNNING HIGH. THE FORECAST CALLS FOR
THE RIVER TO REMAIN JUST BELOW FLOOD STAGE SATURDAY NIGHT AND SUNDAY.
THE LOWEST REACH OF THE CHEHALIS WILL BOUNCE AROUND AT A FOOT OR
LESS BELOW FLOOD STAGE THROUGH SATURDAY. MORE RAIN SATURDAY NIGHT
COULD KEEP THE THE LOWER CHEHALIS NEAR FLOOD STAGE...SO HAVE
EXTENDED THE WATCH THROUGH SUNDAY. EVEN LOCAL INFLOW FROM THE WEAK
SYSTEM ON SATURDAY NIGHT COULD CAUSE THE LOWER CHEHALIS TO APPROACH
FLOOD STAGE...BUT ANY FLOODING WILL BE MINOR.
THE CASCADES RECEIVED A BURST OF RAIN AS THE FRONT PASSED THIS
MORNING. THE NOOKSACK DRAINAGE RECEIVED THE MOST RAIN AND THE
NOOKSACK RIVER ROSE SLIGHTLY...BUT IT APPEARS TO HAVE CRESTED AT ALL
GAUGES AND IS HEADING BACK DOWN...WELL BELOW FLOOD STAGE. OTHER
RIVERS COMING OUT OF THE NORTH AND CENTRAL CASCADES SHOWED SMALL
RISES AND ARE NOW RECEDING. ONE EXCEPTION IS THE UPPER SNOQUALMIE
AND TOLT RIVERS WHICH ARE STILL RISING. HOWEVER RAINFALL AMOUNTS
WERE NOT ENOUGH TO CAUSE ANY PROBLEMS AND THE RIVERS SHOULD HEAD
BACK DOWN SOON.
ANOTHER SYSTEM WILL ARRIVE SATURDAY WITH SIGNIFICANT PRECIPITATION
LATE SATURDAY INTO SATURDAY NIGHT. HOWEVER...THIS SYSTEM IS COLDER
WITH THE MAJORITY OF THE PRECIPITATION BEING SNOW OVER THE
MOUNTAINS. NEW FLOODING IS NOT EXPECTED.
THE NEXT SYSTEM ON MONDAY SHOULD MOVE THROUGH QUICKLY AND BE TOO
WEAK TO CAUSE ANY FLOODING...EVEN WITH RISING SNOW LEVELS. FOR THE
REMAINDER OF THE WEEK...THE AIR MASS OVER THE NORTHWEST WILL BE
WARMER WITH HIGHER SNOW LEVELS...HOWEVER THE SYSTEMS THAT ARE
EXPECTED TO AFFECT THE AREA WILL BE FAIRLY WEAK AND ARE NOT EXPECTED
TO CAUSE ANY ADDITIONAL FLOODING CONCERNS.
NO FLOODING IS EXPECTED AT ANY TIME ON THE GREEN RIVER. BURKE
&&
.AVIATION...AN UPPER TROUGH AXIS WILL MOVE ACROSS WRN WA EARLY THIS
EVENING. THE ATMOSPHERE WILL BE SLIGHTLY UNSTABLE TONIGHT WITH
SHOWERS...AND SLIGHT CHANCE OF ISOLATED THUNDERSTORMS UNTIL AROUND 5
PM. LOW LEVEL MIXING OVERNIGHT SHOULD LIMIT LOWER STRATUS FORMATION
WITH FOG NOT EXPECTED. CIGS WILL GENERALLY RUN VFR THROUGH SAT
MORNING. MODERATE TO STRONG WLY FLOW TONIGHT WILL BECOME STRONG SLY
FLOW ALOFT ON SAT AHEAD OF AN APPROACHING SURFACE LOW AND FRONT.
A PUGET SOUND CONVERGENCE ZONE IS EXPECTED TO FORM EARLY THIS
EVENING NORTH OF EVERETT...THEN SAG SWD TO NEAR THE KING/SNOHOMISH
LINE BY LATE THIS EVENING. THE CONVERGENCE ZONE SHOULD DISSIPATE
EARLY SAT MORNING AS THE FLOW DAMPENS AHEAD OF THE NEXT SYSTEM.
.KSEA...SW WIND 10-14 KT WITH GUSTS UP TO 25 KT OVERNIGHT. THE
CONVERGENCE ZONE MAY REACH AS FAR SOUTH AS NORTH SEATTLE BUT IS NOT
LIKELY TO REACH THE TERMINAL. DTM
.MARINE...STRONG ONSHORE FLOW WITH SW GRADIENTS WARRANT KEEPING
SMALL CRAFT ADVISORIES FOR THE WATERS THROUGH TONIGHT. WILL KEEP
STRONG GALES IN THE CENTRAL AND E STRAIT WITH A STRONG POST FRONTAL
WLY SURGE EXPECTED DOWN THE STRAIT THIS EVENING. WINDS SHOULD EASE A
BIT LATER TONIGHT...POSSIBLY BACK TO SMALL CRAFT BY EARLY SAT
MORNING.
THE NEXT SYSTEM TO AFFECT THE AREA ARRIVES MIDDAY SAT IN THE FORM OF
WARM FRONT TO LIFT ACROSS WRN WA. MODELS DIFFER CONSIDERABLY ON THE
TRAILING SURFACE LOW. ON MODEL SHOWS TWO STRONG SUB 990 MB LOWS
TRACKING INTO VANCOUVER ISLAND AND THE OTHER INTO N OREGON. ANOTHER
MODEL SHOWS ONE SUB 990 MB LOW GOING INTO KHQM ON THE S WA COAST.
THE EXACT TRACK HAS A HIGH IMPACT ON THE WIND SPEEDS SAT AFTERNOON
THROUGH SAT NIGHT. THERE DOES APPEAR TO BE A FAIRLY STRONG FRONT TO
STILL DRAG ACROSS...SO I WILL GO WITH A GALE WATCH FOR NOW AND LET
THE NEXT SHIFT TRY TO FIGURE OUT IF THE SURFACE LOW IS HEADING N OR
S OF WA OR RIGHT ACROSS.
SEAS WILL REMAIN HIGH THROUGH TONIGHT...AROUND 15 FT. ON SAT...SEAS
WILL SUBSIDE SLIGHTLY TO AROUND 12 FT BUT HAZARDOUS SEAS WILL
CONTINUE WITH ROUGH TO SEVERE BAR CONDITIONS. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WA...FLOOD WARNINGS AND/OR FLOOD WATCHES ARE IN EFFECT FOR A
PORTION OF THE CWA.
.A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE CASCADES TNGT.
PZ...A GALE WARNING IS IN EFFECT FOR THE CENTRAL AND EAST STRAIT TIL
MIDNIGHT TONIGHT.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL REMAINING WATERS
THROUGH SAT MORNING.
.A SMALL CRAFT ADVISORY FOR SEVERE BAR CONDITIONS IS IN EFFECT
FOR THE GRAYS HARBOR BAR.
.A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS...EAST
STRAIT...AND NORTH INTERIOR FROM MIDDAY SAT THROUGH SAT
EVENING.
$$
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FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
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