000
FXUS66 KSEW 092300
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST TUE FEB 9 2010
.SYNOPSIS...AN APPROACHING FRONT WILL BRING INCREASING CLOUDS
TONIGHT AND RAIN BY LATE WEDNESDAY AFTERNOON. A STRONGER AND WETTER
FRONTAL SYSTEM WILL AFFECT THE AREA LATE WEDNESDAY NIGHT AND
THURSDAY. STRONGER SOUTHWEST FLOW ALOFT OVER THE REGION WILL SEND
MORE WEATHER SYSTEMS ACROSS THE AREA FRIDAY THROUGH THE WEEKEND.
&&
.SHORT TERM...WESTERN WASHINGTON CLEARED OUT THIS AFTERNOON EXCEPT
FOR A PATCH AROUND SOUTH PUGET SOUND. THIS WILL CONTINUE TO ERODE
BUT THE SUN MAY SET BEFORE IT IS COMPLETELY GONE. OTHERWISE SHOULD
BE A CLEAR EVENING. APPROACHING FRONT WILL SPREAD HIGH THEN MID
CLOUDS OVER THE AREA TONIGHT. THIS WILL LIMIT FOG BUT PATCHY FOG IS
STILL LIKELY IN SUSCEPTIBLE LOCATIONS. OVERNIGHT LOWS SHOULD BE A
BIT HIGHER THAN LAST NIGHT...BUT STILL IN THE 30S AND LOWER 40S.
MODELS HAVE CONVERGED ON A WEDNESDAY SOLUTION THAT HAS RAIN
DEVELOPING ON THE COAST IN THE MORNING AND SPREADING INLAND DURING
THE AFTERNOON. HAVE MOSTLY FOLLOWED THE CATEGORICAL MOS POPS BUT
HAVE SLIGHTLY LOWER POPS FOR THE SEATTLE AREA...JUST LIKELIES.
WESTERLY FLOW ALOFT COULD PUT SEATTLE IN A RAIN SHADOW FOR AWHILE.
AFTER THIS FIRST SYSTEM PASSES WEDNESDAY EVENING...A WARM FRONT
MOVES UP FROM THE SOUTH LATE WEDNESDAY NIGHT. THIS WILL SPREAD RAIN
OVER THE AREA AGAIN AND ALSO BRING BREEZY CONDITIONS TO THE COAST ON
THURSDAY. A COLD FRONT REACHES THE COAST THURSDAY AFTERNOON AND
SWEEPS INLAND THURSDAY NIGHT. HIGH POPS FOR BOTH THESE FRONTS.
FRIDAY MORNING COULD BE MOSTLY DRY WITH JUST SCATTERED SHOWERS BUT
YET ANOTHER SYSTEM ARRIVES FRIDAY AFTERNOON...AND HAVE KEPT LIKELY
POPS FOR THIS SYSTEM. TEMPERATURES WILL REMAIN SEASONAL WITH HIGHS
AROUND 50 AND LOWS AROUND 40. ONE EXCEPTION COULD BE THURSDAY WHEN
THE AREA WILL BE IN THE WARM SECTOR AFTER THE PASSAGE OF THE WARM
FRONT. ON THURSDAY SOME TEMPERATURES WILL REACH THE MID 50S. BURKE
.LONG TERM...AFTER ANOTHER LULL FRIDAY NIGHT AND SATURDAY MORNING...
MODELS BRING ANOTHER SYSTEM INTO THE PACIFIC NORTHWEST. THE EURO
SENDS MOST MOISTURE INTO BRITISH COLUMBIA AND THEN BRINGS A FRONT
THROUGH WASHINGTON ON SUNDAY. THE GFS BRINGS A MORE CONSOLIDATED
FRONT DIRECTLY THROUGH WASHINGTON SATURDAY NIGHT. NEITHER ONE
IS ALL THAT IMPRESSIVE WITH RAINFALL AMOUNTS...EVEN IN THE OLYMPIC
MOUNTAINS. THUS WILL OPT FOR NO STATEMENT ABOUT POTENTIAL FLOODING.
BOTH THE EURO AND GFS HAVE DRY SUNDAY NIGHTS AND MONDAYS AND WET
TUESDAYS. HAVE NOT COMPLETELY BOUGHT THESE SOLUTIONS AND KEPT THE
BROAD BRUSH LIKELY POPS FOR NOW. BURKE
&&
.HYDROLOGY...NOTHING TOO SIGNIFICANT IN THE MODELS THROUGH FRIDAY.
ANY RAIN WILL BE LIGHT TO MODERATE AND RIVERS WILL RISE ONLY
MODERATELY. THE MAIN EFFECT OF THE REPEATED RAIN STORMS WILL BE TO
MOISTEN THE SOIL AND GET THE HYDROLOGICAL SYSTEMS PRIMED AGAIN. BOTH
THE GFS AND EURO HAVE BACKED OFF SOMEWHAT ON RAINFALL AMOUNTS OVER
THE WEEKEND. MOST OF THE MOISTURE IS SHOVED NORTH INTO BRITISH
COLUMBIA. THERE IS STILL A CHANCE OF HEAVY RAIN OVER THE OLYMPIC
MOUNTAINS...ESPECIALLY ON SUNDAY. THE CASCADES DO NOT APPEAR TO BE
UNDER ANY THREAT AND THE PROBABILITY OF FLOODING ON THE GREEN RIVER
IS LOW.
POSSIBLY THE ONLY SIGNIFICANT EFFECT OF ALL THESE STORMS WILL BE TO
INCREASE THE THREAT OF LANDSLIDES IN SATURATED SOIL SLIGHTLY BY NEXT
WEEK. BURKE
&&
.AVIATION...HIGH PRES ALOFT WILL PERSIST THROUGH TONIGHT. MODERATE
SW FLOW ALOFT TONIGHT WILL BECOME STRONG ON WED. THE ATMOSPHERE WILL
BE DRY AND STABLE...BECOMING MOIST DURING THE DAY WED. RAIN WILL
DEVELOP LATE WED MORNING ALONG THE COAST...SPREADING INLAND BY WED
AFTERNOON AS A FRONT MOVE INTO WRN WA. THE COMBINATION OF BREEZY
WINDS AND CLOUDS SHOULD INHIBIT FOG DEVELOPMENT...EXCEPT THIS
EVENING AROUND THE SW INTERIOR AND STRAIT. THESE SPOTS SHOULD
IMPROVE LATER TONIGHT AS SOME MIXING DEVELOPS.
KSEA...VARIABLE WIND 4 KT OR LESS....BECOMING S 5-9 KT AFTER 08Z.
FOG IS UNLIKELY DUE TO SLY BREEZE AND INCREASING HIGH CLOUDS
TONIGHT. LIGHT RAIN AND CIGS 3-4K FT WILL DEVELOP AFTER 18Z THU.
&&
.MARINE...WIND GENERALLY LIGHT TONIGHT...EXCEPT E WIND UP TO 20 KT
AT THE W ENTRANCE TO THE STRAIT. A FRONT WILL BRING SOLID SMALL
CRAFT WINDS TO THE COASTAL WATERS AND W ENTRANCE WED MORNING THROUGH
THE AFTERNOON. WINDS WILL ALSO INCREASE FROM AROUND ADMIRALTY INLET
NWD LATER ON WED. A SMALL CRAFT MAY BE NEEDED FOR THESE AREAS. A
STRONGER FRONT BRINGS MORE WIDESPREAD SMALL CRAFT WINDS AND POSSIBLY
GALES TO THE COASTAL WATERS THU AND THU NIGHT.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
PZ...SMALL CRAFT ADVISORY COAST AND WEST ENTRANCE WEDNESDAY MORNING
THROUGH WEDNESDAY AFTERNOON.
WA...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 091701
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST TUE FEB 9 2010
.SYNOPSIS...AN UPPER LEVEL RIDGE WILL SUNSHINE THIS AFTERNOON AFTER
AREAS OF MORNING FOG CLEAR. AN APPROACHING COLD FRONT WILL BRING
RAIN TO THE AREA BY LATE WEDNESDAY AFTERNOON. A STRONGER AND WETTER
FRONTAL SYSTEM WILL AFFECT THE AREA LATE WEDNESDAY NIGHT AND
THURSDAY. STRONGER SOUTHWEST FLOW ALOFT OVER THE REGION WILL SEND
MORE WEATHER SYSTEMS ACROSS THE AREA FRIDAY THROUGH THE WEEKEND.
&&
.SHORT TERM...FOG BLANKETS THE PUGET SOUND AREA THIS MORNING. ABOVE
THE FOG SKIES ARE CLEAR SO ONCE THE FOG BURNS OFF THERE WILL BE
MOSTLY SUNNY CONDITIONS. EXPECTING THE FOG TO BE MOSTLY GONE BY NOON
OR SO. OVERNIGHT LOWS WERE IN THE 30S SO HIGHS THIS AFTERNOON WILL
BE LUCKY TO REACH 50.
MODELS HAVE SPED UP THE NEXT SYSTEM WHICH IS NOW DUE WEDNESDAY
AFTERNOON. MOS POPS ARE QUITE HIGH FOR THE PERIOD 18Z-00Z WEDNESDAY.
CURRENT FORECAST SAYS LIKELY OR BETTER WHICH MAY BE ENOUGH. RAIN
TURNS TO SHOWERS WEDNESDAY NIGHT. ON THURSDAY MORNING A WARM FRONT
MOVES FROM SOUTH TO NORTH OVER THE AREA...SPREADING RAIN. A COLD
FRONT FOLLOWS THURSDAY NIGHT. ALL THREE MODELS...GFS NAM AND EURO...
ARE IN GOOD AGREEMENT ABOUT THE TIMING OF THESE SYSTEMS.
SOME MINOR DISAGREEMENT EXISTS ABOUT FRIDAY. THE NAM IS PRETTY DRY
UNTIL THE AFTERNOON...THE EURO AND GFS BRING RAIN FROM THE NEXT
SYSTEM A BIT FASTER. NOT SURE WHICH WAY TO JUMP. THE SCREAMING
MESSAGE IS THAT TODAY WILL BE THE LAST DRY DAY FOR AWHILE. BURKE
.LONG TERM...PREVIOUS DISCUSSION...THE HEMISPHERIC PATTERN SHOWS
MINOR CHANGES BETWEEN EARLY THIS WEEK AND LATE THIS WEEK...BUT THIS
WILL IMPACT THE PACIFIC NORTHWEST. 5-WAVE CHARTS SHOW THE MEAN
LONGWAVE UPPER LEVEL RIDGE CURRENTLY OVER THE PACIFIC NORTHWEST
SHIFTING EAST OVER THE ROCKIES BY THURSDAY. SIMULTANEOUSLY THE UPPER
LEVEL TROUGH OVER THE NE PACIFIC DEEPENS SLIGHTLY AND SHIFTS A
LITTLE FURTHER EAST...TO AROUND 150W OR 145W. THIS IS ENOUGH TO SET
UP A MORE ACTIVE SW FLOW ALOFT OVER THE PAC NW THAT WILL PROBABLY
PERSIST INTO EARLY NEXT WEEK. GFS/ECMWF SHOW A FAST-MOVING COLD
FRONT ARRIVING FRIDAY...FOLLOWED BY A STRONGER WARM FRONT/COLD FRONT
COMBO SATURDAY THROUGH EARLY SUNDAY MORNING. LIKELY POPS FOR RAIN AT
TIMES SEEMS REASONABLE FOR THE EXTENDED PERIOD. KAM
&&
.HYDROLOGY...NOTHING TOO SIGNIFICANT IN THE MODELS THROUGH FRIDAY.
ANY RAIN WILL BE LIGHT AND RIVERS WILL RISE ONLY MODERATELY. THE
MAIN EFFECT OF THE REPEATED RAIN STORMS WILL BE TO MOISTEN THE SOIL
AND GET THE HYDROLOGICAL SYSTEMS PRIMED AGAIN. BOTH THE GFS AND EURO
HAVE BACKED OFF SOMEWHAT ON RAINFALL AMOUNTS OVER THE WEEKEND. MOST
OF THE MOISTURE IS SHOVED NORTH INTO BRITISH COLUMBIA. THERE IS
STILL A CHANCE OF HEAVY RAIN OVER THE OLYMPIC MOUNTAINS...ESPECIALLY
ON SUNDAY. THE CASCADES DO NOT APPEAR TO BE UNDER ANY THREAT AND THE
PROBABILITY OF FLOODING ON THE GREEN RIVER IS LOW.
POSSIBLY THE ONLY SIGNIFICANT EFFECT OF ALL THESE STORMS WILL BE TO
INCREASE THE THREAT OF LANDSLIDES IN SATURATED SOIL SLIGHTLY BY NEXT
WEEK. BURKE
&&
.AVIATION...HIGH PRES OVER WA THROUGH TONIGHT WITH LIGHT SW FLOW
ALOFT. STABLE CONDITIONS WITH MOISTURE CONFINED BELOW 1K FT. AREAS
OF FOG WITH VISIBILITY BELOW 1SM IN SPOTS WILL BEGIN TO DISSIPATE
AFTER 18-19Z. FOG MAY LINGER AN HOUR LONGER OVER THE SW INTERIOR.
FOG SHOULD CLEAR ALL AREAS BY 20Z.
KSEA...IFR FOG IS EXPECTED THROUGH 18Z...POSSIBLY LINGERING UNTIL
19Z BUT SHOULD RAPIDLY DISSIPATE THEREAFTER. VFR CONDITIONS THE REST
OF THE DAY. LIGHT WIND. DTM
&&
.MARINE...SEAS BELOW 10 FT THROUGH TONIGHT AND WINDS GENERALLY LESS
THAN 15 KT WITH LIGHT SURFACE GRADIENTS. A FRONT WILL REACH THE
COASTAL WATERS ON WEDNESDAY WITH SOLID SMALL CRAFT WINDS...POSSIBLY
APPROACHING GALE FORCE IN THE OUTER COASTAL WATERS BY MIDDAY. THE
ENTRANCES TO THE STRAIT ARE ALSO AT RISK FOR LOWER END SMALL CRAFT
WINDS BY WEDNESDAY AFTERNOON. ANOTHER SYSTEM WILL CONTINUE THE
STRONGER WINDS OVER THE COASTAL WATERS THROUGH THURSDAY. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 091104 CCA
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
238 AM PST TUE FEB 9 2010
.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BRING AREAS OF MORNING FOG AND
AFTERNOON SUNSHINE TO WESTERN WASHINGTON TODAY. AN APPROACHING COLD
FRONT WILL BRING RAIN TO THE AREA BY LATE WEDNESDAY AFTERNOON. A
STRONGER AND WETTER FRONTAL SYSTEM WILL AFFECT THE AREA LATE
WEDNESDAY NIGHT AND THURSDAY. STRONGER SOUTHWEST FLOW ALOFT OVER THE
REGION WILL SENT ADDITIONAL WEATHER SYSTEMS ACROSS THE AREA FRIDAY
THROUGH THE WEEKEND.
&&
.SHORT TERM...THE LONGWAVE RIDGE OVER THE ROCKIES WILL BE THE
DOMINANT FEATURE TODAY. SUPPORTING THE LONGWAVE RIDGE IS THE
OFFSHORE SHORTWAVE RIDGE APPROACHING 135W. THE UPPER LEVEL SHORTWAVE
TROUGH NEAR 130W IS ALL THAT IS LEFT OF THE SPLITTING SYSTEM THAT
FELL APART JUST OFFSHORE LAST EVENING. CLOUDS FROM THE ASSOCIATED
FRONTAL BAND JUST OFFSHORE DISSIPATED RAPIDLY AFTER 03Z MONDAY
EVENING SO THAT AREAS OF IFR CIGS AND/OR VIS HAVE DEVELOPED AT THE
MAJORITY OF OB SITES. OTHERWISE MOST OTHER SPOTS ARE CLEAR. GFS/NAM
HAVE THIS REMNANT UPPER LEVEL SHORTWAVE TROUGH MOVING OVER THE COAST
AROUND 00Z WITH LITTLE EFFECT.
NAM TIME-HEIGHT SECTIONS SEEM TO HAVE A LOT OF MOISTURE AROUND
3000-5000 FEET OVERNIGHT AND THIS MORNING THAT DOES NOT SHOW UP IN
THE GFS TIME-HEIGHT SECTIONS. NAM DOES NOT SEEM TO HAVE CAUGHT UP TO
THE DRYING SHOWN ON IR IMAGERY SO WILL FOLLOW THE GFS SOLUTION FOR
SKY CONDITION TODAY.
ALL MODELS ARE IN GOOD AGREEMENT SHOWING THE UPSTREAM FRONTAL SYSTEM
CURRENTLY ALONG 140W CHARGING EAST AND REACHING THE AREA WEDNESDAY.
SHOULD SEE CIRRUS INCREASING AT LEAST LATE TONIGHT. 00Z MODEL
GUIDANCE APPEARS TO HAVE SHIFTED TO A FASTER SOLUTION...SO ALL MODEL
AND MOS GUIDANCE NOW SUPPORT AT LEAST LIKELY POPS FOR THE INTERIOR
WEDNESDAY AFTERNOON. WILL RAISE POPS FOR THE COAST TO AT LEAST
LIKELY WEDNESDAY MORNING. SNOW LEVELS WILL BE LOW ENOUGH FOR SNOW TO
REACH THE PASSES...THOUGH IT MAY BE CLOSE AT SNOQUALMIE. NAM 12 HOUR
PRECIP AMOUNTS ARE BELOW SNOW ADVISORY CRITERIA FOR THE MOUNTAINS.
THE PRECIP SHOULD EASE SHORTLY AFTER 00Z AS THE SHORTWAVE TROUGH
MOVES THROUGH. THE SURFACE FRONT MAY END UP DISSIPATING OVER THE
AREA.
ECMWF/GFS ARE IN GOOD AGREEMENT WITH THE NEXT STRONGER SYSTEM LATE
WEDNESDAY NIGHT AND THURSDAY. A WARM FRONT WILL AFFECT THE AREA LATE
WEDNESDAY NIGHT AND THURSDAY MORNING FOLLOWED BY THE COLD FRONT
THURSDAY AFTERNOON/EVENING. SNOW LEVELS WILL BE HIGHER...ESPECIALLY
OVER THE OLYMPICS...AND PRECIP HEAVIER. WINDS ARE BELOW ADVISORY
CRITERIA EXCEPT FOR THE MARINE AREAS. KAM
.LONG TERM...THE HEMISPHERIC PATTERN SHOWS MINOR CHANGES BETWEEN
EARLY THIS WEEK AND LATE THIS WEEK...BUT THIS WILL IMPACT THE
PACIFIC NORTHWEST. 5-WAVE CHARTS SHOW THE MEAN LONGWAVE UPPER LEVEL
RIDGE CURRENTLY OVER THE PACIFIC NORTHWEST SHIFTING EAST OVER THE
ROCKIES BY THURSDAY. SIMULTANEOUSLY THE UPPER LEVEL TROUGH OVER THE
NE PACIFIC DEEPENS SLIGHTLY AND SHIFTS A LITTLE FURTHER EAST...TO
AROUND 150W OR 145W. THIS IS ENOUGH TO SET UP A MORE ACTIVE SW FLOW
ALOFT OVER THE PAC NW THAT WILL PROBABLY PERSIST INTO EARLY NEXT
WEEK. GFS/ECMWF SHOW A FAST-MOVING COLD FRONT ARRIVING
FRIDAY...FOLLOWED BY A STRONGER WARM FRONT/COLD FRONT COMBO SATURDAY
THROUGH EARLY SUNDAY MORNING. LIKELY POPS FOR RAIN AT TIMES SEEMS
REASONABLE FOR THE EXTENDED PERIOD. KAM
&&
.HYDROLOGY...A SLIGHT SHIFT IN THE HEMISPHERIC PATTERN WILL ALLOW
STRONGER SW FLOW ALOFT TO DEVELOP OVER W WA FROM MID-WEEK ONWARD. A
COLD FRONT ON WEDNESDAY WILL BE THE FIRST SYSTEM TO REACH THE AREA.
A STRONGER WARM FRONT/COLD FRONT COMBO MAY BRING SOME HEAVIER RAIN
TO THE AREA LATE WEDNESDAY NIGHT/THURSDAY...WITH A SHORT PERIOD OF
45-50KT SW WINDS ALOFT OVER THE OLYMPICS. 06Z NAM 24 HOUR PRECIP
SHOWS OVER 2.5 INCHES OVER THE OLYMPICS ENDING THURSDAY EVENING.
THIS PROBABLY WON`T CAUSE ANY FLOODING BUT WILL CAUSE RISES ON
OLYMPIC RIVERS.
A FAST MOVING COLD FRONT ON FRIDAY PROBABLY WON`T ADD SIGNIFICANT
PRECIP TO THE AREA. HOWEVER A STRONGER SYSTEM ARRIVING THIS WEEKEND
HAS MORE POTENTIAL FOR HEAVY RAIN. EXPECT ANOTHER ROUND OF 50-60KT
SW FLOW ALOFT. THIS SYSTEM LOOKS STRONGER AND WETTER THAN THE
THURSDAY SYSTEM...WITH A LONGER DURATION OVER W WA. ECMWF IS A
LITTLE QUICKER.
LIKE PREVIOUS WET SYSTEMS THIS SEASON...THE STRONG SW FLOW ALOFT
WITH THE TWO SYSTEMS MENTIONED ABOVE WILL AFFECT MAINLY THE
OLYMPICS...AND TO A LESSER EXTENT THE N CASCADES. THE PROBABILITY OF
FLOODING ON THE GREEN RIVER...IN THE CENTRAL CASCADES IS LOW. KAM
&&
.AVIATION...AREAS OF FOG OR LOW STRATUS ARE OVER WESTERN WA...THEY
WILL LIKELY DISPERSE AND MIX OUT MIDDAY...WITH A FEW OF THE MORE
STUBBORN LOCATIONS LIKE OLYMPIA POSSIBLY IN THE AFTERNOON. THE FLOW
SFC AND ALOFT IS LIGHT AND NOT UNTIL AROUND DAYBREAK WED DOES THE
FLOW ALF PICK UP. THE MODELS SHOW RATHER A LOT OF MOISTURE SPREADING
INTO WRN WA WED MORNING...SO THERE IS A GOOD CHANCE THAT AFTER
PATCHY FOG TONIGHT SKIES TURN CLOUDY RATHER RAPIDLY WED MORNING. 19
KSEA...CURRENT TAF IS THE BEST GUESS FOR THE MORNING FOG...IN SOME
PLACES THE FOG HAS LIFTED TO A LOW STRATUS DECK BUT THAT WONT HELP
KSEA UP ON THE HILL. SKIES SHOULD CLEAR MIDDAY AS THE FOG DISPERSES
AND MIXES OUT. AS SLY FLOW DEVELOPS WED MORNING CLOUDS WILL QUICKLY
INCREASE AND SO I DO NOT EXPECT A REPEAT OF THE FOG WED MORNING.
&&
.MARINE...A SERIES OF PROGRESSIVELY STRONGER FRONTAL SYSTEMS WILL
AFFECT THE AREA STARTING WED...COASTAL SLY GALES ARE FAIRLY CERTAIN
BY LATE IN THE WEEK. TODAY WILL BE A QUIET DAY WITH LIGHT OFFSHORE
FLOW...MORNING FOG...AND THEN LIGHT SLY FLOW INCREASING ON WED WITH
THE FIRST FRONT.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 091037
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
238 AM PST TUE FEB 9 2010
.SYNOPSIS...AN UPPER LEVEL RIDGE WILL BRING AREAS OF MORNING FOG AND
AFTERNOON SUNSHINE TO WESTERN WASHINGTON TODAY. AN APPROACHING COLD
FRONT WILL BRING RAIN TO THE AREA BY LATE WEDNESDAY AFTERNOON. A
STRONGER AND WETTER FRONTAL SYSTEM WILL AFFECT THE AREA LATE
WEDNESDAY NIGHT AND THURSDAY. STRONGER SOUTHWEST FLOW ALOFT OVER THE
REGION WILL SENT ADDITIONAL WEATHER SYSTEMS ACROSS THE AREA FRIDAY
THROUGH THE WEEKEND.
&&
.SHORT TERM...THE LONGWAVE RIDGE OVER THE ROCKIES WILL BE THE
DOMINANT FEATURE TODAY. SUPPORTING THE LONGWAVE RIDGE IS THE
OFFSHORE SHORTWAVE RIDGE APPROACHING 135W. THE UPPER LEVEL SHORTWAVE
TROUGH NEAR 130W IS ALL THAT IS LEFT OF THE SPLITTING SYSTEM THAT
FELL APART JUST OFFSHORE LAST EVENING. CLOUDS FROM THE ASSOCIATED
FRONTAL BAND JUST OFFSHORE DISSIPATED RAPIDLY AFTER 03Z MONDAY
EVENING SO THAT AREAS OF IFR CIGS AND/OR VIS HAVE DEVELOPED AT THE
MAJORITY OF OB SITES. OTHERWISE MOST OTHER SPOTS ARE CLEAR. GFS/NAM
HAVE THIS REMNANT UPPER LEVEL SHORTWAVE TROUGH MOVING OVER THE COAST
AROUND 00Z WITH LITTLE EFFECT.
NAM TIME-HEIGHT SECTIONS SEEM TO HAVE A LOT OF MOISTURE AROUND
3000-5000 FEET OVERNIGHT AND THIS MORNING THAT DOES NOT SHOW UP IN
THE GFS TIME-HEIGHT SECTIONS. NAM DOES NOT SEEM TO HAVE CAUGHT UP TO
THE DRYING SHOWN ON IR IMAGERY SO WILL FOLLOW THE GFS SOLUTION FOR
SKY CONDITION TODAY.
ALL MODELS ARE IN GOOD AGREEMENT SHOWING THE UPSTREAM FRONTAL SYSTEM
CURRENTLY ALONG 140W CHARGING EAST AND REACHING THE AREA WEDNESDAY.
SHOULD SEE CIRRUS INCREASING AT LEAST LATE TONIGHT. 00Z MODEL
GUIDANCE APPEARS TO HAVE SHIFTED TO A FASTER SOLUTION...SO ALL MODEL
AND MOS GUIDANCE NOW SUPPORT AT LEAST LIKELY POPS FOR THE INTERIOR
WEDNESDAY AFTERNOON. WILL RAISE POPS FOR THE COAST TO AT LEAST
LIKELY WEDNESDAY MORNING. SNOW LEVELS WILL BE LOW ENOUGH FOR SNOW TO
REACH THE PASSES...THOUGH IT MAY BE CLOSE AT SNOQUALMIE. NAM 12 HOUR
PRECIP AMOUNTS ARE BELOW SNOW ADVISORY CRITERIA FOR THE MOUNTAINS.
THE PRECIP SHOULD EASE SHORTLY AFTER 00Z AS THE SHORTWAVE TROUGH
MOVES THROUGH. THE SURFACE FRONT MAY END UP DISSIPATING OVER THE
AREA.
ECMWF/GFS ARE IN GOOD AGREEMENT WITH THE NEXT STRONGER SYSTEM LATE
WEDNESDAY NIGHT AND THURSDAY. A WARM FRONT WILL AFFECT THE AREA LATE
WEDNESDAY NIGHT AND THURSDAY MORNING FOLLOWED BY THE COLD FRONT
THURSDAY AFTERNOON/EVENING. SNOW LEVELS WILL BE HIGHER...ESPECIALLY
OVER THE OLYMPICS...AND PRECIP HEAVIER. WINDS ARE BELOW ADVISORY
CRITERIA EXCEPT FOR THE MARINE AREAS. KAM
.LONG TERM...THE HEMISPHERIC PATTERN SHOWS MINOR CHANGES BETWEEN
EARLY THIS WEEK AND LATE THIS WEEK...BUT THIS WILL IMPACT THE
PACIFIC NORTHWEST. 5-WAVE CHARTS SHOW THE MEAN LONGWAVE UPPER LEVEL
RIDGE CURRENTLY OVER THE PACIFIC NORTHWEST SHIFTING EAST OVER THE
ROCKIES BY THURSDAY. SIMULTANEOUSLY THE UPPER LEVEL TROUGH OVER THE
NE PACIFIC DEEPENS SLIGHTLY AND SHIFTS A LITTLE FURTHER EAST...TO
AROUND 150W OR 145W. THIS IS ENOUGH TO SET UP A MORE ACTIVE SW FLOW
ALOFT OVER THE PAC NW THAT WILL PROBABLY PERSIST INTO EARLY NEXT
WEEK. GFS/ECMWF SHOW A FAST-MOVING COLD FRONT ARRIVING
FRIDAY...FOLLOWED BY A STRONGER WARM FRONT/COLD FRONT COMBO SATURDAY
THROUGH EARLY SUNDAY MORNING. LIKELY POPS FOR RAIN AT TIMES SEEMS
REASONABLE FOR THE EXTENDED PERIOD. KAM
&&
.HYDROLOGY...A SLIGHT SHIFT IN THE HEMISPHERIC PATTERN WILL ALLOW
STRONGER SW FLOW ALOFT TO DEVELOP OVER W WA FROM MID-WEEK ONWARD. A
COLD FRONT ON WEDNESDAY WILL BE THE FIRST SYSTEM TO REACH THE AREA.
A STRONGER WARM FRONT/COLD FRONT COMBO MAY BRING SOME HEAVIER RAIN
TO THE AREA LATE WEDNESDAY NIGHT/THURSDAY...WITH A SHORT PERIOD OF
45-50KT SW WINDS ALOFT OVER THE OLYMPICS. 06Z NAM 24 HOUR PRECIP
SHOWS OVER 2.5 INCHES OVER THE OLYMPICS ENDING THURSDAY EVENING.
THIS PROBABLY WON`T CAUSE ANY FLOODING BUT WILL CAUSE RISES ON
OLYMPIC RIVERS.
A FAST MOVING COLD FRONT ON FRIDAY PROBABLY WON`T ADD SIGNIFICANT
PRECIP TO THE AREA. HOWEVER A STRONGER SYSTEM ARRIVING THIS WEEKEND
HAS MORE POTENTIAL FOR HEAVY RAIN. EXPECT ANOTHER ROUND OF 50-60KT
SW FLOW ALOFT. THIS SYSTEM LOOKS STRONGER AND WETTER THAN THE
THURSDAY SYSTEM...WITH A LONGER DURATION OVER W WA. ECMWF IS A
LITTLE QUICKER.
LIKE PREVIOUS WET SYSTEMS THIS SEASON...THE STRONG SW FLOW ALOFT
WITH THE TWO SYSTEMS MENTIONED ABOVE WILL AFFECT MAINLY THE
OLYMPICS...AND TO A LESSER EXTENT THE N CASCADES. THE PROBABILITY OF
FLOODING ON THE GREEN RIVER...IN THE CENTRAL CASCADES IS LOW. KAM
&&
.AVIATION...AREAS OF FOG OR LOW STRATUS ARE OVER WESTERN WA...THEY
WILL LIKELY DISPERSE AND MIX OUT MIDDAY...WITH A FEW OF THE MORE
STUBBORN LOCATIONS LIKE OLYMPIA POSSIBLY IN THE AFTERNOON. THE FLOW
SFC AND ALOFT IS LIGHT AND NOT UNTIL AROUND DAYBREAK WED DOES THE
FLOW ALF PICK UP. THE MODELS SHOW RATHER A LOT OF MOISTURE SPREADING
INTO WRN WA WED MORNING...SO THERE IS A GOOD CHANCE THAT AFTER
PATCHY FOG TONIGHT SKIES TURN CLOUDS RATHER RAPIDLY WED MORNING. 19
KSEA...CURRENT TAF IS THE BEST GUESS FOR THE MORNING FOG...IN SOME
PLACES THE FOG HAS LIFTED TO A LOW STRATUS DECK BUT THAT WONT HELP
KSEA UP ON THE HILL. SKIES SHOULD CLEAR MIDDAY AS THE FOG DISPERSES
AND MIXES OUT. AS SLY FLOW DEVELOPS MONDAY MORNING CLOUDS WILL
QUICKLY INCREASE AND SO I DO NOT EXPECT A REPEAT OF THE FOG WED
MORNING.
&&
.MARINE...A SERIES OF PROGRESSIVELY STRONGER FRONTAL SYSTEMS WILL
AFFECT THE AREA STARTING WED...COASTAL SLY GALES ARE FAIRLY CERTAIN
BY LATE IN THE WEEK. TODAY WILL BE A QUIET DAY WITH LIGHT OFFSHORE
FLOW...MORNING FOG...AND THEN LIGHT SLY FLOW INCREASING ON WED WITH
THE FIRST FRONT.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 090533
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 PM PST MON FEB 8 2010
.SYNOPSIS...A BUBBLE OF HIGH PRESSURE WILL BUILD OVER WESTERN AND
CENTRAL WASHINGTON FOR THE REST OF TONIGHT...BRINGING DRY AND STABLE
CONDITIONS THROUGH TUESDAY NIGHT. A CHANCE OF RAIN WILL DEVELOP
WEDNESDAY AFTERNOON AND EVENING...AND RAIN WILL BE LIKELY ON
THURSDAY. A MORE ACTIVE WEATHER PATTERN WILL CONTINUE INTO THE
WEEKEND WITH RAIN LIKELY AT TIMES.
&&
.SHORT TERM...THE MID-LEVEL LOW CONTINUES TO MOVE SE AND IS NOW OFF
THE NRN CALIFORNIA COAST. IT HAS BASICALLY HAD NO EFFECT ON WRN
WA...AND IT NEVER CAUSED RAIN TO SPREAD ONTO THE COAST. THAT WINDOW
OF OPPORTUNITY IS NOW OVER...SO HAVE REMOVED MENTION OF COASTAL RAIN
FROM THE FORECAST FOR THE REST OF TONIGHT.
OTHERWISE...TODAY WAS STILL AND STABLE. WAS HARD TO MUSTER ANY
WIND...AND STABLE CONDITIONS CAUSED A BROWN HAZE TO DEVELOP ON THE
HORIZON AROUND THE METRO AREA. WITH A SMALL UPPER HIGH DEVELOPING
OVER CNTRL WA THIS EVENING AND DECREASING COVERAGE OF MID-LEVEL
CLOUDS...LOCALIZED AREAS OF FOG STARTED FORMING ALMOST AS SOON AS
THE SUN HAD SET. KOLM...KTCM...KTIW...KCLS AND KPLU ALREADY HAVE
VSBYS BELOW 1SM...AND FOG COVERAGE SHOULD ONLY INCREASE THROUGH THE
NIGHT. THEREFORE INCREASED COVERAGE OF FOG IN THE FORECAST TONIGHT
AND TUE MORNING.
SOME MID-LEVEL DRYING ON TUE SHOULD ALLOW PLENTY OF AFTERNOON
SUNSHINE ONCE MORNING FOG BURNS OFF...THOUGH THAT COULD BE SLOW IN A
FEW SPOTS GIVEN NEARLY CALM WIND AND A STABLE AIR MASS.
THE JET STREAM FLOW OVER THE ERN PAC WILL START TO STRENGTHEN AND
CONSOLIDATE AROUND THE MIDDLE OF THIS WEEK. THIS WILL BE THE FIRST
MAJOR PATTERN SHIFT FOR THE PAC NW IN A FEW WEEKS WITH WETTER AND
STRONGER STORM SYSTEMS EXPECTED TO START IMPACTING WRN WA. THE FIRST
SYSTEM WILL PUSH A WARM FRONT ONSHORE ON WED EVNG...ACCOMPANIED BY
AN INCREASE IN WIND AND SOME RAIN ON WED AND WED NIGHT. HANER
.LONG TERM...FROM PREVIOUS DISCUSSION...ONCE THE SYSTEM PASSES
THURSDAY...THE DOOR APPEARS OPEN FOR MORE SYSTEMS. THE PATTERN
BECOMES ACTIVE WITH STORMS MOVING MAINLY INTO BRITISH COLUMBIA BUT
ALSO BRUSHING WASHINGTON. THE GFS AND EURO ARE IN BROAD AGREEMENT
ABOUT THE CHANGE TO MORE VIGOROUS WEATHER. SUNDAY LOOKS PRETTY WET
IN THE GFS...ENOUGH TO MAKE RIVERS ON THE OLYMPIC PENINSULA RESPOND.
MONDAY COULD BE COOLER AND MORE SHOWERY. HAVE BROAD BRUSHED THE
FORECAST WITH LIKELY POPS FRIDAY THROUGH MONDAY. THERE WILL BE SOME
DRIER PERIODS DURING THAT TIME AND HAVE USED RAIN LIKELY AT TIMES
WORDING. THE SNOW LEVEL WILL BOUNCE AROUND BETWEEN 3000 AND 5000
FEET...FINISHING THE WEEKEND AT THE LOWER END. BURKE
&&
.HYDROLOGY...PREVIOUS DISCUSSION REMAINS VALID AND FOLLOWS...NOTHING
REALLY SIGNIFICANT HAPPENS IN THE MODELS UNTIL THE WEEKEND. THERE
WILL BE SOME RAIN ON THURSDAY AND FRIDAY BUT AMOUNTS ARE
UNIMPRESSIVE...RIVERS WILL RISE BUT NOT TOO MUCH. THESE EVENTS WILL
SERVE TO GET THE GROUND WET AGAIN HOWEVER. IF THE GFS IS RIGHT
SUNDAY COULD BRING HYDROLOGICALLY SIGNIFICANT RAINFALL TO THE
OLYMPIC PENINSULA. THE EURO IS EVEN FASTER WITH THE HEAVY RAIN
BEGINNING ON SATURDAY. NOT REALLY READY TO PUT OUT A STATEMENT BUT
THIS BEARS WATCHING.
ANY HEAVY RAIN IS CURRENTLY AIMED AT THE OLYMPIC MOUNTAINS AND
POSSIBLY THE NORTH CASCADES. THE PROBABILITY OF FLOODING ON THE
GREEN RIVER...IN THE CENTRAL CASCADES...IS LOW. BURKE
&&
.AVIATION...LIGHT OFFSHORE FLOW AND CLEARING SKIES HAVE ALLOWED
AREAS OF 1/4FG TO DEVELOP ALREADY...ESPECIALLY TACOMA TO OLYMPIA.
AREAS OF FOG WILL CONTINUE TO DEVELOP AND SPREAD OUT OVERNIGHT...BUT
BY MIDDAY TUE THE FOG AND ANY AREAS OF LOW STRATUS SHUD DISPERSE AND
MIX OUT...ALTHOUGH IT COULD BE A STRUGGLE AROUND OLYMPIA. 19
KSEA...A GOOD SHOT AT GETTING FOG OVERNIGHT...OR A MIX OF FOG AND
LOW STRATUS. WILL WATCH THE DEW POINTS AND THE OBS...THE LIGHT NLY
GRADIENT SHOULD HELP TO KEEP THE 1/4FG AROUND TACOMA TO THE
SOUTH...BUT AFTER AREAS OF FOG DEVELOP ON THE EAST SIDE AND OVER
SNOHOMISH COUNTY IT WONT TAKE LONG TO START FILLING IN OVER THE
METRO AREA AS WELL...PARTLY ADVECTING IN FROM THE NE AND PARTLY
RADIATIONAL FORMING AS WELL. 19
&&
.MARINE...WEATHER SYSTEM JUST OFFSHORE BREAKING UP AND
SPLITTING...WEAK SFC TROF. LIGHT NE GRADIENTS THRU TUE. EACH FRONT
WED THU FRI SAT IS SUCCESSIVELY STRONGER IN THE MODELS SO THE TREND
BACK UP TO COASTAL GALES BY THE WEEKEND LOOKS GOOD. 19
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
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000
FXUS66 KSEW 082239
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PST MON FEB 8 2010
.SYNOPSIS...A WEAK FRONT WILL BRING A CHANCE OF RAIN TO THE COAST
TONIGHT BUT WILL NOT AFFECT THE INTERIOR. TUESDAY AND TUESDAY NIGHT
WILL BE DRY. A CHANCE OF RAIN WILL DEVELOP WEDNESDAY AFTERNOON AND
EVENING...AND RAIN WILL BE LIKELY ON THURSDAY. A MORE ACTIVE WEATHER
PATTERN WILL CONTINUE INTO THE WEEKEND WITH RAIN LIKELY AT TIMES.
&&
.SHORT TERM...PRETTY GOOD CLEARING THIS AFTERNOON IN THE STRIP
BETWEEN PUGET SOUND AND THE CASCADES AND ALSO IN THE SOUTHWEST. THE
COAST BEGAN THE DAY UNDER CLOUDS...CLEARED OUT...AND HAS CLOUDED UP
AGAIN. WEAK FRONT APPARENT IN SATELLITE IMAGERY WILL KEEP CLOUDS ON
THE COAST TONIGHT AND EVEN BRING A CHANCE OF RAIN THERE. THIS FRONT
IS FORECAST TO DISSIPATE OFFSHORE AND NOT BRING ANY RAIN INLAND.
HOWEVER HIGH AND MID LEVEL CLOUDS WILL INCREASE THIS EVENING AND
MOST OF THE NIGHT WILL BE OVERCAST...PROBABLY OVER THE WHOLE CWA.
AFTER SOME PATCHY MORNING FOG THERE SHOULD BE GOOD BREAKOUT MOST
AREAS ON TUESDAY. DRY CONDITIONS WILL PREVAIL THROUGH TUESDAY NIGHT
AND INTO WEDNESDAY. THE NEXT SYSTEM WILL BRING A CHANCE OF RAIN TO
THE COAST WEDNESDAY MORNING AND SPREAD THAT CHANCE INLAND DURING THE
DAY. CLOUDS WILL INCREASE WEDNESDAY AND OVERCAST CONDITIONS WILL
CONTINUE INTO THURSDAY. A STRONGER SYSTEM...WHICH LOOKS A LITTLE
LIKE A WARM FRONT/COLD FRONT PAIR...ARRIVES THURSDAY AND THURSDAY
NIGHT. HAVE LIKELY POPS FOR THIS SYSTEM. AMOUNTS ARE NOT TOO
IMPRESSIVE BUT EVERYWHERE IS LIKELY TO SEE A LITTLE RAIN. HIGH
TEMPERATURES WILL BE IN THE UPPER 40S TO LOW 50S ALL THREE DAYS
THROUGH THURSDAY. BURKE
.LONG TERM...ONCE THE SYSTEM PASSES THURSDAY...THE DOOR APPEARS OPEN
FOR MORE SYSTEMS. THE PATTERN BECOMES ACTIVE WITH STORMS MOVING
MAINLY INTO BRITISH COLUMBIA BUT ALSO BRUSHING WASHINGTON. THE GFS
AND EURO ARE IN BROAD AGREEMENT ABOUT THE CHANGE TO MORE VIGOROUS
WEATHER. SUNDAY LOOKS PRETTY WET IN THE GFS...ENOUGH TO MAKE RIVERS
ON THE OLYMPIC PENINSULA RESPOND. MONDAY COULD BE COOLER AND MORE
SHOWERY. HAVE BROAD BRUSHED THE FORECAST WITH LIKELY POPS FRIDAY
THROUGH MONDAY. THERE WILL BE SOME DRIER PERIODS DURING THAT TIME
AND HAVE USED RAIN LIKELY AT TIMES WORDING. THE SNOW LEVEL WILL
BOUNCE AROUND BETWEEN 3000 AND 5000 FEET...FINISHING THE WEEKEND AT
THE LOWER END. BURKE
&&
.HYDROLOGY...NOTHING REALLY SIGNIFICANT HAPPENS IN THE MODELS UNTIL
THE WEEKEND. THERE WILL BE SOME RAIN ON THURSDAY AND FRIDAY BUT
AMOUNTS ARE UNIMPRESSIVE...RIVERS WILL RISE BUT NOT TOO MUCH. THESE
EVENTS WILL SERVE TO GET THE GROUND WET AGAIN HOWEVER. IF THE GFS IS
RIGHT SUNDAY COULD BRING HYDROLOGICALLY SIGNIFICANT RAINFALL TO THE
OLYMPIC PENINSULA. THE EURO IS EVEN FASTER WITH THE HEAVY RAIN
BEGINNING ON SATURDAY. NOT REALLY READY TO PUT OUT A STATEMENT BUT
THIS BEARS WATCHING.
ANY HEAVY RAIN IS CURRENTLY AIMED AT THE OLYMPIC MOUNTAINS AND
POSSIBLY THE NORTH CASCADES. THE PROBABILITY OF FLOODING ON THE
GREEN RIVER...IN THE CENTRAL CASCADES...IS LOW. BURKE
&&
.AVIATION...LOW LEVEL STRATUS WAS SLOW TO CLEAR OUT THIS AFTERNOON
WITH LIGHT SFC FLOW AND WEAK MIXING. STILL SEEING LOCAL CIGS AROUND
005-010 IN THE INTERIOR WHICH MAY ONLY BRIEFLY MIX OUT THIS EVENING.
OTHERWISE...WILL SEE SOME CLEARING TONIGHT WITH AREAS OF FOG
EXPECTED BY MORNING. A WEAKENING FRONT OVER THE COASTAL WATERS MAY
BRING LIGHT RAIN TO THE COAST TONIGHT...WITH DRY CONDITIONS EXPECTED
FOR THE INTERIOR. 33
KSEA...WINDS WILL REMAIN LIGHT AND VARIABLE TONIGHT WITH WEAK
PRESSURE GRADIENTS ACROSS THE INTERIOR. LOW LEVEL CLOUDS WILL MIX
OUT THIS EVENING WITH CLEARING TONIGHT...THEN FOG DEVELOPING IN THE
VICINITY LATE. LITTLE CHANGE EXPECTED IN THE FORECAST. 33
&&
.MARINE...A WEAKENING FRONT WILL DISSIPATE OVER THE COASTAL WATERS
TONIGHT...WITH LIGHT SURFACE FLOW ACROSS THE REGION. LIGHT WINDS ARE
ANTICIPATED THROUGH TUE NIGHT. A SERIES OF STRONGER SYSTEMS WILL
IMPACT WESTERN WA WED THROUGH FRI...LEADING TO STRONGER S/SE WINDS
OVER THE WATERS WITH SWELLS BUILDING OVER 15 FT. 33
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
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000
FXUS66 KSEW 081633
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 AM PST MON FEB 8 2010
.SYNOPSIS...DEVELOPING HIGH PRESSURE AT THE SURFACE AND ALOFT OVER
THE INLAND NORTHWEST WILL GIVE MAINLY DRY CONDITIONS TODAY. ANOTHER
SPLITTING FRONT WILL AFFECT COASTAL AREAS THIS AFTERNOON THROUGH
TONIGHT. THIS FRONT WILL DRIVE SOUTHEAST TOWARD CALIFORNIA AND NOT
MAKE IT INTO THE INTERIOR OF WESTERN WASHINGTON. AFTER ANOTHER DRY
PERIOD ON TUESDAY AND TUESDAY NIGHT...STRONGER SYSTEMS WILL AFFECT
THE REGION STARTING LATE WEDNESDAY. A MORE ACTIVE PATTERN WILL
CONTINUE INTO NEXT WEEKEND.
&&
.SHORT TERM...SATELLITE IMAGERY AND SURFACE OBS SHOW THE CASCADES
AND AREAS JUST WEST ARE MAINLY IN THE CLEAR...AS ARE A FEW OTHER
AREAS AROUND THE OLYMPICS. HOWEVER THE WHOLE PUGET SOUND AREA IS
COVERED BY CLOUDS IN SEVERAL LAYERS. THE LOWEST LAYER IS STRATUS AND
FOG AND HAVE ISSUED A NOWCAST FOR PATCHY FOG LASTING A FEW MORE
HOURS. ABOVE THIS LOWEST LAYER ARE MORE CLOUDS. UPSHOT IS IT WILL
PROBABLY TAKE AWHILE TO GET ANY CLEARING GOING. PARTLY SUNNY IS
PROBABLY THE BEST PUGETOPOLIS CAN MANAGE THIS AFTERNOON. A WEAK
SYSTEM WILL DIE OFF THE COAST TONIGHT...SO THOUGH THERE MAY BE
CLEARING ON THE COAST THIS AFTERNOON...IT LIKELY WILL BE BRIEF AS
CLOUDS ASSOCIATED WITH THE SYSTEM MOVE IN.
SHOULD BE SOMEWHAT SUNNIER TUESDAY AFTERNOON. CLOUDS ARE LIKELY TO
REFORM OVERNIGHT TONIGHT BUT BOTH THE GFS AND NAM SHOW LESS MOISTURE
IN THE AREA AND BOTH MOS SKY COVERS SHOW LOTS OF SCATTERED CLOUD
AREAS BY TUESDAY AFTERNOON. BOTH MODELS AS WELL AS THE EURO SHOW A
WEAK SYSTEM BRINGING SOME MOISTURE ASHORE ON WEDNESDAY. TEMPERATURES
WILL PEAK AROUND 50 TODAY AND TOMORROW...AND COULD BE A FEW DEGREES
LOWER ON WEDNESDAY IF CLOUDS AND A LITTLE RAIN ARRIVE. BURKE
.LONG TERM...PREVIOUS DISCUSSION...WHILE THE MODELS CONTINUE TO HAVE
CONSISTENCY ISSUES FROM RUN TO RUN THERE IS A GENERAL TREND THAT THE
FLOW ALOFT OFFSHORE WILL CONSOLIDATE SOMEWHAT DURING THE LATTER PART
OF THE EXTENDED PERIOD. SYSTEMS ON BOTH THURSDAY AND FRIDAY SHOWING
VARYING DEGREES OF SPLITTING IN THE MODELS. OVER THE WEEKEND THE
FLOW ALOFT OFF THE COAST DOES CONSOLIDATE OUT OF THE SOUTHWEST. THE
QUESTION WILL BE WHERE DOES THE JET SET UP. RIGHT NOW THE MODELS ARE
INDICATING THE JET WILL BE AIMED AT VANCOUVER ISLAND WITH WESTERN
WASHINGTON GETTING THE TAIL END OF THE FRONTS. WITH THE CONSOLIDATED
FLOW ALOFT THE SYSTEMS OVER THE WEEKEND WILL BE STRONGER AND WETTER.
A SLIGHT SHIFT SOUTH IN THE JET COULD PUT WESTERN WASHINGTON IN A
VERY WET PATTERN FOR THE WEEKEND. THE END RESULT OF ALL OF THIS WILL
GO WITH A BROADBRUSH OF LIKELY POPS FOR NOW THROUGH THE EXTENDED
PERIOD WITH TEMPERATURES NEAR NORMAL. FELTON
&&
.HYDROLOGY...PREVIOUS DISCUSSION...CONDITIONS WILL GENERALLY BE DRY
THROUGH WEDNESDAY ACROSS WESTERN WASHINGTON INTERIOR. BEYOND
WEDNESDAY WEATHER SYSTEMS ARRIVING IN THE AREA LOOK TO BE A LITTLE
STRONGER VERSUS THE SYSTEMS MOVING THROUGH IN THE PAST FEW DAYS.
EVEN WITH THE STRONGER SYSTEMS...A SPLIT IN THE UPPER LEVEL FLOW OFF
THE COAST WILL REMAIN AT LEAST FOR THURSDAY AND FRIDAY WHICH WILL
KEEP PRECIPITATION AMOUNTS BELOW HYDROLOGICALLY SIGNIFICANT LEVELS.
MODEL RUNS THIS MORNING FOR THE FIRST TIME HAVE A MORE CONSOLIDATED
FLOW ALOFT DEVELOPING OVER THE WEEKEND WITH A VERY WET PATTERN
SETTING UP. RIGHT NOW THE JET IS AIMED AT VANCOUVER ISLAND WITH
WESTERN WASHINGTON GETTING THE TAIL END OF THE FRONTS. IF THE JET
ENDS UP BEING A LITTLE FURTHER SOUTH...A SMALL ERROR IN THE MODELS
THIS FAR OUT...WESTERN WASHINGTON COULD BE IN FOR A SPELL OF HEAVY
PRECIPITATION ESPECIALLY IN THE OLYMPICS AND TO A LESSER EXTENT THE
NORTHERN CASCADES. RIVERS WILL BE STARTING FROM LOW LEVELS ON THE
WEEKEND SO IT WILL TAKE A GOOD SHOT OF PRECIPITATION TO GET THE
RIVERS UP CLOSE TO FLOOD STAGE. THE SYSTEM OVER THE WEEKEND HAS THE
POTENTIAL TO DO JUST THAT IF IT ENDS UP A LITTLE FURTHER SOUTH THEN
THE CURRENT MODEL SOLUTIONS. BEYOND THE WEEKEND A WEAK UPPER LEVEL
RIDGE IS FORECAST TO BUILD OVER WESTERN WASHINGTON WITH THE
PRECIPITATION COMING TO AN END.
GIVEN THE UNCERTAINTY OF THE SITUATION WILL STILL CONSIDER THE FLOOD
THREAT LOW OVER THE REGION FOR THE NEXT 10 DAYS BUT WE WILL BE
KEEPING A CLOSE EYE ON THE MODEL SOLUTIONS FOR THE WEEKEND. THE LOW
FLOOD THREAT INCLUDES THE GREEN RIVER. FELTON
&&
.AVIATION...FOG AND LOW STRATUS HAS FILLED IN OVER THE INTERIOR FROM
ABOUT EVERETT SOUTHWARD THROUGH THE INTERIOR VALLEYS. PRESSURE
GRADIENTS ARE FLAT AND MIXING IS POOR. SOME LAYERS AT 035 AND 060
WILL LIKELY INHIBIT INSOLATION THROUGH THE EARLY AFTERNOON HOURS.
WILL LIKELY NEED TO HOLD ONTO LOW STRATUS WITH BASES 007-010 UNTIL
ABOUT 20Z-21Z.
A WEAKENING FRONT IN THE OFFSHORE WATERS PULLS OFF TO THE SOUTHEAST
WELL SOUTH OF WESTERN WASHINGTON TONIGHT. THIS FRONT WILL HAVE
LITTLE EFFECT ON THE AREA EXCEPT ON THE COAST WHERE MID AND HIGH
LEVEL MOISTURE AND AREAS -RA MOVES RIGHT TO THE COASTLINE AROUND 00Z
THEN DISSIPATES. WEAK HIGH PRES DEVELOPS OVER W WA...AND THIS HIGH
WILL GIVE SUBSIDENCE...SOME CLEARING...AND LIGHT PRES GRADIENTS. THE
END RESULT WILL BE THE DEVELOPMENT OF AREAS OF FOG TONIGHT THAT WILL
LIKELY PERSIST TO AFTER ABOUT NOON ON TUE.
KSEA...EXPECT SLOW IMPROVEMENT 18Z-21Z WITH SCATTERING OF THE LAYER
AROUND 010 BY 21Z. CLOUD LAYERS AT 035 AND 060 WILL GRADUALLY
SCATTER OUT LATE THIS AFTERNOON AND EVENING. EXPECT FOG TO FORM OVER
THE SOUND AND VALLEYS TO THE EAST OF THE TERMINAL AFTER ABOUT
10Z...AND THIS WILL MOVE INTO THE TERMINAL 12Z-14Z AND CONTINUE
THROUGH 18Z-20Z TUE. EXPECT VERY LIGHT WINDS THROUGH THE PERIOD.
ALBRECHT
&&
.MARINE...A WEAKENING FRONT IN THE OFFSHORE WATERS WILL DRIVE TO THE
SOUTHEAST...WELL SOUTH OF THE WATERS...LATER THIS AFTERNOON AND
TONIGHT. A BRIEF PERIOD OF SE WIND 10 TO 20 KT IN THE COASTAL WATERS
WILL OCCUR THIS AFTERNOON AND EVENING BUT WILL BECOME LIGHT E/NE
LATER TONIGHT THROUGH TUE NIGHT. VERY LIGHT WINDS ARE EXPECTED IN
THE INLAND WATERS WITH HIGH PRES AND FLAT PRES GRADIENTS.
STRONGER SE FLOW WILL DEVELOP WED AFTERNOON AND WED NIGHT AHEAD OF A
STRONGER FRONTAL SYSTEM. THERE ARE A COUPLE OF CHANCES TO REACH
SOUTHERLY GALE IN THE COASTAL WATERS THU AND FRI. ALBRECHT
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY GRAYS HARBOR BAR THROUGH 2 PM THIS
AFTERNOON.
$$
WWW.WEATHER.GOV/SEATTLE
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000
FXUS66 KSEW 081157
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
355 AM PST MON FEB 8 2010
.SYNOPSIS...DEVELOPING HIGH PRESSURE AT THE SURFACE AND ALOFT OVER
THE INLAND NORTHWEST WILL GIVE MAINLY DRY CONDITIONS TODAY. ANOTHER
SPLITTING FRONT WILL AFFECT COASTAL AREAS THIS AFTERNOON THROUGH
TONIGHT. THIS FRONT WILL DRIVE SOUTHEAST TOWARD CALIFORNIA AND NOT
MAKE IT INTO THE INTERIOR OF WESTERN WASHINGTON. AFTER ANOTHER DRY
PERIOD ON TUESDAY AND TUESDAY NIGHT...STRONGER SYSTEMS WILL AFFECT
THE REGION STARTING LATE WEDNESDAY. A MORE ACTIVE PATTERN WILL
CONTINUE INTO NEXT WEEKEND.
&&
.SHORT TERM...SATELLITE IMAGERY SHOWS CLOUD COVER OVER MOST OF
WESTERN WASHINGTON AT 11Z. NONE OF THE SURFACE OBS REPORTING ANY
SHOWER ACTIVITY BUT THE WSR-88D STILL HAS A COUPLE OF PRECIPITATION
ECHOES. THESE SHOWERS WILL COME TO AN END IN THE NEXT COUPLE OF
HOURS. SURFACE GRADIENTS LIGHT THIS MORNING WITH FOG FORMING
ANYPLACE WHERE THERE IS A LITTLE BREAK IN THE OVERCAST. WITH THE
FLAT GRADIENTS AND PLENTY OF LOW LEVEL MOISTURE THE CLOUD COVER IS
KEEPING THE FOG FROM BECOMING WIDESPREAD. NOT MUCH CHANGE IN THE
THINKING FOR THE FORECAST THIS MORNING. NEXT APPROACHING FRONT BACK
OUT NEAR 130W AT 11Z WITH THE PARENT LOW NEAR 49N/134W. THE LOW HAS
BEGUN MOVING SOUTHEAST IN THE LAST FEW HOURS. THIS TRACK WILL
CONTINUE THROUGHOUT THE DAY WITH THE LOW SOMEWHERE WEST OF THE
OREGON CALIFORNIA BORDER BY 06Z TONIGHT. AS THE LOW MOVES SOUTHEAST
THE FRONT WILL ELONGATE AND WEAKEN OFF THE COAST TODAY AND THEN MOVE
SOUTHEAST AND DISSIPATE TONIGHT. THE FRONT WILL GET CLOSE ENOUGH TO
THE COAST LATER TODAY INTO TONIGHT FOR A CHANCE OF RAIN ALONG THE
COAST. FOR THE REMAINDER OF THE AREA JUST MOSTLY CLOUDY SKIES. WEAK
UPPER LEVEL RIDGE TRYING TO BUILD OFF THE COAST TUESDAY WITH THE
RIDGE MOVING INLAND TUESDAY NIGHT AND A WEAK UPPER LEVEL TROUGH
RIDING BY TO THE NORTH. SURFACE GRADIENTS STILL FAIRLY FLAT ON
TUESDAY SO EVEN THOUGH MORE SUNSHINE IS EXPECTED ESPECIALLY IN THE
AFTERNOON MAX TEMPERATURES WILL BE NEAR TODAYS VALUES. WEDNESDAY IS
A TRANSITION DAY FROM THE STRONG SPLIT FLOW ALOFT OFF THE COAST TO A
WEAKER SOMEWHAT MORE CONSOLIDATED FLOW ALOFT ALONG THE PACIFIC
NORTHWEST COAST. BOTH THE GFS AND ECMWF BRING PRECIPITATION INTO THE
AREA BY 00Z THU. THE CANADIAN IS A LITTLE SLOWER WITH THE ARRIVAL OF
THE PRECIPITATION. THE CANADIAN MODEL HAS BEEN THE MOST CONSISTENT
RUN TO RUN FOR THE LAST FEW DAYS AND WILL GO WITH THE SLOWER TIMING
FOR NOW.
.LONG TERM...WHILE THE MODELS CONTINUE TO HAVE CONSISTENCY ISSUES
FROM RUN TO RUN THERE IS A GENERAL TREND THAT THE FLOW ALOFT
OFFSHORE WILL CONSOLIDATE SOMEWHAT DURING THE LATTER PART OF THE
EXTENDED PERIOD. SYSTEMS ON BOTH THURSDAY AND FRIDAY SHOWING VARYING
DEGREES OF SPLITTING IN THE MODELS. OVER THE WEEKEND THE FLOW ALOFT
OFF THE COAST DOES CONSOLIDATE OUT OF THE SOUTHWEST. THE QUESTION
WILL BE WHERE DOES THE JET SET UP. RIGHT NOW THE MODELS ARE
INDICATING THE JET WILL BE AIMED AT VANCOUVER ISLAND WITH WESTERN
WASHINGTON GETTING THE TAIL END OF THE FRONTS. WITH THE CONSOLIDATED
FLOW ALOFT THE SYSTEMS OVER THE WEEKEND WILL BE STRONGER AND WETTER.
A SLIGHT SHIFT SOUTH IN THE JET COULD PUT WESTERN WASHINGTON IN A
VERY WET PATTERN FOR THE WEEKEND. THE END RESULT OF ALL OF THIS
WILL GO WITH A BROADBRUSH OF LIKELY POPS FOR NOW THROUGH THE
EXTENDED PERIOD WITH TEMPERATURES NEAR NORMAL. FELTON
&&
.HYDROLOGY...CONDITIONS WILL GENERALLY BE DRY THROUGH WEDNESDAY
ACROSS WESTERN WASHINGTON INTERIOR. BEYOND WEDNESDAY WEATHER SYSTEMS
ARRIVING IN THE AREA LOOK TO BE A LITTLE STRONGER VERSUS THE SYSTEMS
MOVING THROUGH IN THE PAST FEW DAYS. EVEN WITH THE STRONGER
SYSTEMS...A SPLIT IN THE UPPER LEVEL FLOW OFF THE COAST WILL REMAIN
AT LEAST FOR THURSDAY AND FRIDAY WHICH WILL KEEP PRECIPITATION
AMOUNTS BELOW HYDROLOGICALLY SIGNIFICANT LEVELS. MODEL RUNS THIS
MORNING FOR THE FIRST TIME HAVE A MORE CONSOLIDATED FLOW ALOFT
DEVELOPING OVER THE WEEKEND WITH A VERY WET PATTERN SETTING UP.
RIGHT NOW THE JET IS AIMED AT VANCOUVER ISLAND WITH WESTERN
WASHINGTON GETTING THE TAIL END OF THE FRONTS. IF THE JET ENDS UP
BEING A LITTLE FURTHER SOUTH...A SMALL ERROR IN THE MODELS THIS FAR
OUT...WESTERN WASHINGTON COULD BE IN FOR A SPELL OF HEAVY
PRECIPITATION ESPECIALLY IN THE OLYMPICS AND TO A LESSER EXTENT THE
NORTHERN CASCADES. RIVERS WILL BE STARTING FROM LOW LEVELS ON THE
WEEKEND SO IT WILL TAKE A GOOD SHOT OF PRECIPITATION TO GET THE
RIVERS UP CLOSE TO FLOOD STAGE. THE SYSTEM OVER THE WEEKEND HAS THE
POTENTIAL TO DO JUST THAT IF IT ENDS UP A LITTLE FURTHER SOUTH THEN
THE CURRENT MODEL SOLUTIONS. BEYOND THE WEEKEND A WEAK UPPER LEVEL
RIDGE IS FORECAST TO BUILD OVER WESTERN WASHINGTON WITH THE
PRECIPITATION COMING TO AN END.
GIVEN THE UNCERTAINTY OF THE SITUATION WILL STILL CONSIDER THE FLOOD
THREAT LOW OVER THE REGION FOR THE NEXT 10 DAYS BUT WE WILL BE
KEEPING A CLOSE EYE ON THE MODEL SOLUTIONS FOR THE WEEKEND. THE LOW
FLOOD THREAT INCLUDES THE GREEN RIVER. FELTON
&&
.AVIATION...IT IS A HODGE PODGE OF CONDITIONS EARLY THIS MORNING
WHERE SOME AREAS HAVE FOGGED IN AS THE MAIN CLOUD LAYER HAS BROKEN
UP...OTHER AREAS HAVE LOW STRATUS...AND SOME AREAS REMAIN OVC050
WITH NO LOW STRATUS OR FOG. PRES GRADIENTS ARE QUITE LIGHT OVER WRN
WA...AND THERE IS ONLY LIGHT FLOW ALF. A WEAK FRONT WILL BREAK UP
JUST OFFSHORE LATER TODAY...AND THE LOW LEVEL MOIST AIR MASS WILL
GIVE WAY TO MID AND HIGH CLOUDS FROM THAT SYSTEM THIS AFTERNOON.
KSEA...CONDITIONS DID NOT DETERIORATE OVERNIGHT AS I EXPECTED SO
CONFIDENCE IN THE TAF THIS MORNING IS LOW...AND CONDITIONS ARE
RATHER VARIABLE ACROSS WRN WA THIS MORNING...IT WILL BE TRICKY TIL
18Z.
&&
.MARINE...LIGHT FLOW. A WEAKENING FRONT WILL DISSIPATE OVER THE
COASTAL WATERS THIS AFTERNOON AND EVENING. STRONGER SE FLOW WILL
DVLP WED AHEAD OF A STRONGER FRONTAL SYSTEM WITH A COUPLE OF CHANCES
TO REACH SLY GALES COASTAL WATERS THU AND FRI. 19
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY GRAYS HARBOR BAR.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 080529
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
928 PM PST SUN FEB 7 2010
.SYNOPSIS...A WEAK UPPER LEVEL TROUGH WILL MOVE EAST OF THE CASCADES
AND WEAKEN OVERNIGHT. DEVELOPING HIGH PRESSURE AT THE SURFACE AND
ALOFT OVER THE INLAND NORTHWEST WILL GIVE MAINLY DRY CONDITIONS AND
LIGHT OFFSHORE FLOW MONDAY. ANOTHER SPLITTING FRONT WILL AFFECT
COASTAL AREAS MONDAY AFTERNOON AND NIGHT. THIS FRONT WILL DRIVE
SOUTHEAST TOWARD CALIFORNIA AND NOT MAKE IT INTO THE INTERIOR OF
WESTERN WASHINGTON. AFTER ANOTHER DRY PERIOD ON TUESDAY AND TUESDAY
NIGHT...STRONGER SYSTEMS WILL AFFECT THE REGION STARTING LATE
WEDNESDAY. A MORE ACTIVE PATTERN WILL CONTINUE THROUGH NEXT WEEKEND.
&&
.SHORT TERM...PRESSURE GRADIENTS ACROSS WRN WA ARE ABOUT AS FLAT AS
THEY GET. HAS BEEN HARD TO FIND ANYWHERE TODAY WITH EVEN A PUFF OF
WIND. STILL HAVE LOTS OF MOISTURE BELOW 700 MB...AND SOME SHALLOW
INSTABILITY BETWEEN 925 AND 850 MB CONTINUES TO SUPPORT ISOLATED
SHOWERS. THE ATMOSPHERE SHOULD STABILIZE SLOWLY OVERNIGHT...AND A
LITTLE DRYING WILL TAKE PLACE ON MONDAY...SO EXPECTING ISOLATED
SHOWER COVERAGE TO ONLY WANE OVERNIGHT AND EARLY MONDAY MORNING.
THE NEXT WEATHER FEATURE OF CONSEQUENCE WILL BE THE MID-LEVEL LOW
CENTER CURRENTLY NEAR 49N 138W. THIS LOW WILL SOON START TO MOVE
SOUTHEAST...CROSSING 130W WEST OF THE MOUTH OF THE COLUMBIA AND
EVENTUALLY REACHING THE COAST WAY DOWN NEAR THE SFO BAY AREA. AS THE
LOW CENTER MAKES IT CLOSEST PASS TO WRN WA ON MON AFTN...SOME RAIN
SHOULD SPREAD ONTO THE COAST. AS THE LOW SINKS SOUTH OF OUR LATITUDE
AND FURTHER AWAY...LARGE-SCALE LIFT WILL MOVE AWAY AS WELL...
PREVENTING RAIN FROM EVER REACHING THE INTERIOR. THE LARGE-SCALE
UPPER HIGH OVER THE CANADIAN ROCKIES WILL ULTIMATELY BE TOO MUCH FOR
THIS SYSTEM TO OVERCOME...SO SOME RAIN ON THE COAST ON MON AFTN AND
EVNG IS ALL TO EXPECT.
AS THE MID-LEVEL LOW SINKS S-SE TO THE NRN CAL COAST ON TUE...A
DIFFUSE UPPER HIGH WILL BUILD OVER THE PAC NW...SUPPORTING A DRY DAY
FOR ALL OF WRN WA ON TUE WITH A LOT MORE SUNSHINE.
BY WED...THE UPPER HIGH THAT HAS PREVAILED RECENTLY OVER SW CANADA
SHOULD MIGRATE N-NW TOWARD THE YUKON. THIS WILL ALLOW SOME OF THE
SOUTHERN STREAM ENERGY WHICH HAS FOCUSED LATELY ON CALIFORNIA TO
SHIFT FURTHER NORTH ALONG THE U.S. WEST COAST. THE LEADING SYSTEM IN
THIS MORE ACTIVE SETUP SHOULD PUSH A WARM FRONT ACROSS WRN WA LATE
WED AND WED NIGHT. THIS SHOULD BE THE NEXT WIDESPREAD PRECIP
PRODUCER FOR WRN WA. HANER
.LONG TERM...FROM PREVIOUS DISCUSSION...WHILE MODELS CONTINUE TO
HAVE CONSISTENCY AND CONTINUITY PROBLEMS THU ONWARD...THEY ALL
GENERALLY AGREE THAT WE WILL BE MOVING INTO A MORE ACTIVE WEATHER
PATTERN BEGINNING. NONE OF THE SYSTEMS APPEAR VERY STRONG AS SPLIT
FLOW DOMINATES IN THE MEAN...BUT IT APPEARS THAT WE SHOULD BE SEEING
SLIGHTLY HIGHER RAINFALL AMOUNTS WITH THE SYSTEMS AND SOME MOUNTAIN
SNOWFALL. GIVEN THE TIMING ISSUES AND THE TENDENCY FOR MODELS TO
MOVE TOWARD STRETCHING OUT OF SYSTEMS AS THE TIME APPROACHES...WILL
BROADBRUSH THE LONG TERM WITH LIKELY POPS...HIGHS AROUND 50...AND
LOWS IN THE LOWER 40S. ALBRECHT
&&
.HYDROLOGY...CONDITIONS WILL GENERALLY BE DRY THROUGH WED OR WED
NIGHT. BEYOND WEDNESDAY NIGHT... WEATHER SYSTEMS ARRIVING IN THE
AREA LOOK TO BE A LITTLE STRONGER VERSUS THE SYSTEMS MOVING THROUGH
IN THE PAST FEW DAYS. EVEN WITH THE STRONGER SYSTEMS...A SPLIT IN
THE UPPER LEVEL FLOW OFF THE COAST WILL REMAIN. HEAVIER
PRECIPITATION AMOUNTS BEGINNING THU BUT ESPECIALLY NEXT
WEEKEND...WILL LIKELY RESULT IN SOME RISES IN AREA RIVERS. HOWEVER
RAINFALL IS NOT EXPECTED TO BE HIGH ENOUGH TO RESULT IN AND RIVERS
APPROACHING OR EXCEEDING FLOOD STAGE.
THE FLOOD THREAT WILL REMAIN RATHER LOW OVER THE REGION FOR THE NEXT
10 DAYS...INCLUDING THE GREEN RIVER. ALBRECHT
&&
.AVIATION...WEAK HIGH PRES OVER THE AREA...ONLY VERY MINOR 500MB
HEIGHT RISES TONIGHT...AND AT THE SFC LIGHT OFFSHORE GRADIENTS WITH
SFC HIGH PRES CENTERED WELL INLAND NEAR THE BC/ALTA BORDER. THE
GRADIENTS OVER WRN WA ARE ALL LESS THAN -1MB...AND THE CROSS CASCADE
GRADIENT IS ACTUALLY POSITIVE DESPITE THE BROAD SYNOPTIC SCALE
GRADIENT BEING OFFSHORE. WITH PLENTY OF MOISTURE BELOW ABOUT 800MB
LOOK FOR AREAS OF MIST OR DRIZZLE...SOME LOCAL FOG DEVELOPING...AND
CIGS THAT ARE LIKELY TO FALL THRU THE NIGHT...PLUS LOWER LAYERS THAT
DEVELOP THRU THE NIGHT WITH AREAS IFR CIGS AND VSBY DVLPG AND THE
MTNS PROBABLY OBSCURED THRU MON MORNING. 19
KSEA...CONDITIONS WILL LIKELY DETERIORATE THRU THE NIGHT AND THE
3/4SM BR ALREADY AROUND TACOMA AT 7PM THIS EVENING SUGGESTS IT IS
GOING TO BE A MURKY NIGHT. 19
&&
.MARINE...LIGHT FLOW. A WEAKENING FRONT WILL DISSIPATE OVER THE
COASTAL WATERS MON AFTERNOON AND EVENING. STRONGER SE FLOW WILL
DVLP WED AHEAD OF A STRONGER FRONTAL SYSTEM. A MORE SIGNIFICANT SYS
IS POSSIBLE LATER IN THE WEEK FOR POTENTIAL GALES AND 20 FT SEAS THU
OR FRI. 19
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS REMAINS IN EFFECT FOR
THE COASTAL WATERS THRU TONIGHT.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
REMAINS IN EFFECT THRU TONIGHT.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 072303
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST SUN FEB 7 2010
.SYNOPSIS...A WEAK UPPER LEVEL TROUGH OVER THE AREA WILL MOVE EAST
AND WEAKEN THIS EVENING. DEVELOPING HIGH PRESSURE AT THE SURFACE AND
ALOFT OVER THE INLAND NORTHWEST WILL GIVE MAINLY DRY CONDITIONS AND
LIGHT OFFSHORE FLOW LATER TONIGHT INTO MONDAY. ANOTHER SPLITTING
FRONT WILL AFFECT MAINLY THE COASTAL AREAS MONDAY NIGHT. THIS FRONT
WILL DRIVE SOUTHEAST TOWARD CALIFORNIA AND NOT MAKE IT INTO THE
INTERIOR OF WASHINGTON. AFTER ANOTHER DRY DAY OR TWO TUESDAY AND
WEDNESDAY... STRONGER SYSTEMS WILL AFFECT THE REGION LATE IN THE
WEEK THROUGH NEXT WEEKEND.
&&
.SHORT TERM...WHILE THE FLOW ACROSS THE PACIFIC AND NORTH AMERICA
WILL REMAIN SPLIT FOR THE NEXT WEEK OR MORE...IN LINE WITH THE
CURRENT EL NINO...IT APPEARS THAT HEIGHTS OVER THE PACIFIC NORTHWEST
ARE FALLING SOMEWHAT. THIS WOULD INDICATE THAT TEMPERATURES WOULD
FALL TO A BIT CLOSER TO NORMAL OVER THE SHORT TERM ...THOUGH STILL
ABOVE NORMAL... AND THAT STRONGER SYSTEMS WOULD START AFFECTING THE
AREA LATER IN THE WEEK THROUGH NEXT WEEKEND FOR SOME NEEDED RAIN AND
MOUNTAIN SNOW.
A WEAK UPPER LEVEL TROUGH ASSOCIATED WITH A DYING FRONTAL SYSTEM IS
MOVING NE INTO BRITISH COLUMBIA. SHOWER ACTIVITY WITH THIS SYSTEM
HAS ALL BUT DIED OUT. WITH MORE LOW LEVEL MOISTURE IN PLACE AND ONLY
VERY LIGHT OFFSHORE FLOW...TONIGHT`S FORECAST OF CLOUDS AND LOW
TEMPERATURES IS TRICKY. ANY CLEARING WILL ALLOW NORMALLY COLDER
OUTLYING VALLEYS TO FALL INTO THE 30S. AREAS OF FOG CAN BE EXPECTED
IN VALLEYS THAT GET SOME RADIATIONAL COOLING. THE OFFSHORE FLOW WILL
NOT BE STRONG ENOUGH AT ANY TIME OVER THE NEXT FEW DAYS TO TOTALLY
SCOUR OUT THE LOW LEVEL MOISTURE.
MONDAY WILL GENERALLY BE DRY AS THE NEXT IN A SERIES OF SPLITTING
FRONTAL SYSTEMS APPROACHES FROM THE WEST. PRECIPITATION WITH THIS
FRONT WILL POSSIBLY MOVE ONTO THE COAST...BUT THE MAIN THRUST OF
THIS FRONT IS TOWARD THE SOUTHEAST AS WEAK HIGH PRES ALOFT DEVELOPS
FROM SE BRITISH COLUMBIA INTO SW IDAHO. THIS WILL RESULT IN THE
FRONT QUICKLY STRETCHING APART AS IT MOVES ONSHORE ...AND A MAJORITY
OF THE MODELS SHOW NO PRECIPITATION MAKING IT INTO THE
INTERIOR MONDAY NIGHT.
MORE VERY WEAK RIDGING INLAND AND WEAK OFFSHORE FLOW RESULTS IN
MAINLY DRY CONDITIONS TUESDAY INTO AT LEAST THE FIRST HALF OF
WEDNESDAY.
500 MB HEIGHTS AND 1000-500 MB THICKNESSES INDICATE THAT THE AIR
MASS OVER THE NORTHWEST WILL BE SLIGHTLY COOLER THAN WHAT HAS
OCCURRED OVER THE PAST WEEK OR TWO. WHILE STILL A BIT ABOVE NORMAL
FOR EARLY TO MID FEB...TEMPERATURES ARE STILL EXPECTED TO RUN A FEW
DEG COOLER THAN THE MID AND UPPER 50S OF LATE. ALBRECHT
.LONG TERM...WHILE MODELS CONTINUE TO HAVE CONSISTENCY AND
CONTINUITY PROBLEMS THU ONWARD...THEY ALL GENERALLY AGREE THAT WE
WILL BE MOVING INTO A MORE ACTIVE WEATHER PATTERN BEGINNING. NONE OF
THE SYSTEMS APPEAR VERY STRONG AS SPLIT FLOW DOMINATES IN THE
MEAN...BUT IT APPEARS THAT WE SHOULD BE SEEING SLIGHTLY HIGHER
RAINFALL AMOUNTS WITH THE SYSTEMS AND SOME MOUNTAIN SNOWFALL. GIVEN
THE TIMING ISSUES AND THE TENDENCY FOR MODELS TO MOVE TOWARD
STRETCHING OUT OF SYSTEMS AS THE TIME APPROACHES...WILL BROADBRUSH
THE LONG TERM WITH LIKELY POPS...HIGHS AROUND 50...AND LOWS IN THE
LOWER 40S. ALBRECHT
&&
.HYDROLOGY...CONDITIONS WILL GENERALLY BE DRY THROUGH WED OR WED
NIGHT. BEYOND WEDNESDAY NIGHT... WEATHER SYSTEMS ARRIVING IN THE
AREA LOOK TO BE A LITTLE STRONGER VERSUS THE SYSTEMS MOVING THROUGH
IN THE PAST FEW DAYS. EVEN WITH THE STRONGER SYSTEMS...A SPLIT IN
THE UPPER LEVEL FLOW OFF THE COAST WILL REMAIN. HEAVIER
PRECIPITATION AMOUNTS BEGINNING THU BUT ESPECIALLY NEXT
WEEKEND...WILL LIKELY RESULT IN SOME RISES IN AREA RIVERS. HOWEVER
RAINFALL IS NOT EXPECTED TO BE HIGH ENOUGH TO RESULT IN AND RIVERS
APPROACHING OR EXCEEDING FLOOD STAGE.
THE FLOOD THREAT WILL REMAIN RATHER LOW OVER THE REGION FOR THE NEXT
10 DAYS...INCLUDING THE GREEN RIVER. ALBRECHT
&&
.AVIATION...THE WEAK...UPPER TROF OVER WRN WA THIS AFTERNOON WILL
MOVE E OF THE AREA LATE TODAY OR EARLY THIS EVENING. EXPECT HIGH
PRES ALOFT TO FOLLOW IN ITS WAKE. GENERALLY WLY FLOW ALOFT WILL
BECOME LIGHT SLY ON MON AS ANOTHER UPPER TROF APPROACHES. THE LOW
LEVEL FLOW WILL REMAIN LIGHT OFFSHORE.
MEANWHILE...CLOUDS STUBBORNLY LINGERED OVER THE AREA THIS AFTERNOON.
IN FACT...DO NOT SEE MUCH CLEARING TONIGHT DUE TO LINGERING MOISTURE
AND WEAK FLOW IN THE BOUNDARY LAYER. WILL ALSO SEE MID AND HIGH
CLOUDS INCREASING OVERNIGHT AHEAD OF THE UPPER TROF OFFSHORE. WILL
LEAN TOWARD THE NAM MODEL IN REGARDS TO CIGS IN THE UPCOMING TAF
PACKAGE. SUSPECT THAT THE GFS SOLUTION WAS TOO OPTIMISTIC. ALL IN
ALL...THE FORECAST FOR TONIGHT WILL BE A CHALLENGE AS FAR AS CIGS
ARE CONCERNED. FOG SHOULD BE PATCHY TONIGHT.
KSEA...AS STATED IN THE PREVIOUS PARAGRAPH...WILL FOLLOW THE NAM
GUIDANCE OF LOWER CIGS OVERNIGHT. THUS ANTICIPATE CIGS TO BE
GENERALLY IN THE 2-4K FT RANGE TONIGHT. FOG IS NO LONGER EXPECTED AT
THE TERMINAL.
&&
.MARINE...LIGHT OFFSHORE FLOW WILL PERSIST OVER THE AREA THROUGH MON
DUE TO CONTINUED LOW PRES OVER THE ERN PAC...AND HIGHER PRES INLAND.
EXPECT A WEAKENING OCCLUDED FRONT TO DISSIPATE AS IT APPROACHES THE
COASTAL WATERS MON EVENING. THE FLOW WILL BECOME LIGHT ONSHORE ON
TUE AS HIGH PRES BRIEFLY BUILDS OVER THE ERN PAC. OFFSHORE FLOW WILL
RETURN ON WED AHEAD OF A STRONGER FRONTAL SYSTEM.
A MORE SIGNIFICANT PAC STORM MAY AFFECT THE AREA LATE THIS WEEK FOR
THE POTENTIAL FOR GALE FORCE WINDS AND SEAS APPROACHING 20 FEET ON
THE COASTAL WATERS.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS REMAINS IN EFFECT FOR
THE WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA TIL 6 PM THIS
EVENING.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS REMAINS IN EFFECT FOR
THE COASTAL WATERS THRU TONIGHT.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
REMAINS IN EFFECT THRU TONIGHT.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE).
000
FXUS66 KSEW 071714
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PST SUN FEB 7 2010
.SYNOPSIS...AN AREA OF VERY LIGHT SHOWERS ASSOCIATED WITH A
DISSIPATING FRONTAL SYSTEM IN THE INTERIOR OF WESTERN WASHINGTON
WILL DIMINISH MIDDAY. HIGH PRESSURE AT THE SURFACE AND ALOFT OVER
THE INLAND NORTHWEST WILL GIVE DRY CONDITIONS AND LIGHT OFFSHORE
FLOW TONIGHT INTO MONDAY. ANOTHER SPLITTING FRONT WILL AFFECT
MAINLY THE COASTAL AREAS MONDAY NIGHT. SLIGHTLY STRONGER SYSTEMS
WILL AFFECT THE REGION LATER IN THE WEEK TO COME...GIVING LIGHT RAIN
AT TIMES AND BREEZY CONDITIONS. TEMPERATURES WILL REMAIN ABOVE
NORMAL THROUGH THE WEEK.
&&
.SHORT TERM...A WEAK UPPER LEVEL TROUGH ASSOCIATED WITH A DYING
FRONTAL SYSTEM IS SITTING OVER WESTERN WASHINGTON THIS MORNING. THIS
FEATURE WAS JUST STRONG ENOUGH TO GIVE SOME LIGHT RAIN WITH AREAS OF
DRIZZLE AND FOG TO MUCH OF THE INTERIOR. WHAT IS LEFT OF THE
PRECIPITATION NOW SITS GENERALLY NORTH OF A LINE FROM SEATAC AIRPORT
NW TO VICTORIA B.C. AND IS LIFTING ONLY SLOWLY NORTHWARD. WILL
UPDATE THE ZONES THIS MORNING TO SLOW THE CLEARING OUT THIS
AFTERNOON AND TO HOLD ONTO SOME POPS OVER THE NORTHERN HALF OF THE
INTERIOR THROUGH THE EARLY AFTERNOON HOURS. AFTERNOON HIGHS WILL BE
A COUPLE DEG LOWER THAN PREVIOUSLY EXPECTED AND WILL TEND TO OCCUR
LATER IN THE AFTERNOON.
WITH MORE LOW LEVEL MOISTURE IN PLACE AND ONLY VERY LIGHT OFFSHORE
FLOW...CLOUDS AND LOW TEMPERATURES TONIGHT WILL BE TRICKY. ANY
CLEARING WILL ALLOW NORMALLY COLDER OUTLYING VALLEYS TO FALL INTO
THE 30S. AREAS OF FOG CAN BE EXPECTED IN VALLEYS THAT GET SOME
RADIATIONAL COOLING.
MONDAY WILL GENERALLY BE DRY AS THE NEXT IN A SERIES OF SPLITTING
FRONTAL SYSTEMS APPROACHES FROM THE WEST. HOWEVER MAXIMUM
TEMPERATURES ON MONDAY MAY NOT BE QUITE AS HIGH AS PREVIOUSLY
EXPECTED AS FLOW ALOFT WILL BE LIGHT AND A WEAK PRE FRONTAL RIDGE
ALONG THE COASTAL AREAS KEEPS PRES GRADIENTS FROM GOING OFFSHORE.
THE LIGHTER OFFSHORE PRES GRADIENTS ALSO APPEAR TO BE DUE TO THE
WEAKER AND EVEN SPLITTIER NATURE OF THE INCOMING FRONT WHOSE ENERGY
IS DIRECTED SE INTO CALIFORNIA. NEW GUIDANCE NEVER BRINGS THE FRONT
INLAND AS HEIGHTS RISE OVER THE INLAND NW AND SE BRITISH COLUMBIA.
WITH THE STRONGER RIDGE TUESDAY LOOKS MUCH LIKE MONDAY...AND WED
LOOKS INCREASINGLY DRY.
DAYTIME TEMPERATURES WILL REMAIN 2-4 DEG ABOVE NORMAL THROUGH WED.
WILL UPDATE THE FORECAST TO REFINE SHORT PERIOD POPS...SKY
CONDITIONS AND TEMPERATURES. ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...GFS AND ECMWF
STILL NOT SHOWING MUCH CONSISTENCY ON THE 00Z RUN. THE CANADIAN
MODEL HAS BEEN CONSISTENT FOR THE LAST FOUR NIGHT WITH ITS SOLUTION
AND THE FORECASTS WILL TREND TOWARD THAT MODEL THIS MORNING. UPPER
LEVEL PATTERN REMAINING SPLIT OFF THE COAST THROUGH LATE THURSDAY.
FLOW ALOFT BECOMING MORE CONSOLIDATED BEGINNING FRIDAY WHICH WILL
ALLOW SOME STRONGER WEATHER SYSTEMS TO REACH THE AREA. CONFIDENCE
STILL NOT RUNNING VERY HIGH WITH THE VARIABILITY IN THE EXTENDED
SOLUTIONS. FOR NOW WILL STAY WITH THE CHANCE POPS FOR WEDNESDAY
THROUGH THURSDAY NIGHT WHICH IS IN LINE WITH THE CANADIAN SOLUTION.
THE ECMWF AND THE GFS BOTH BRING A SPLITTING BUT STILL INTACT SYSTEM
INTO WESTERN WASHINGTON ON THURSDAY. WILL UP THE POPS TO LIKELY FOR
FRIDAY AND SATURDAY WITH LESS SPLIT IN THE UPPER LEVEL FLOW
OFFSHORE. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH THE PERIOD.
FELTON
&&
.HYDROLOGY...ONLY VERY LIGHT PRECIPITATION OCCURRED WITH THE
DISSIPATING FRONT LAST NIGHT AND THIS MORNING. CONDITIONS WILL
GENERALLY BE DRY THROUGH WED OR WED NIGHT. BEYOND WEDNESDAY NIGHT...
WEATHER SYSTEMS ARRIVING IN THE AREA LOOK TO BE A LITTLE STRONGER
VERSUS THE SYSTEMS MOVING THROUGH IN THE PAST FEW DAYS. EVEN WITH
THE STRONGER SYSTEMS...A SPLIT IN THE UPPER LEVEL FLOW OFF THE COAST
WILL REMAIN...AT LEAST THROUGH THURSDAY. THE ECMWF BRINGS A COUPLE
OF STRONGER AND WETTER SYSTEMS INTO WESTERN WASHINGTON LATER
THURSDAY AND FRIDAY. THE OTHER EXTENDED MODELS ARE WEAKER AND HAVE
LESS PRECIPITATION. FROM SATURDAY ONWARD THE FLOW ALOFT BECOMES
SPLIT ONCE AGAIN LEAVING ONLY WEAKENING SYSTEMS WITHOUT
HYDROLOGICALLY SIGNIFICANT RAINFALL TO PASS THROUGH THE AREA. THE
FLOOD THREAT WILL REMAIN LOW OVER THE REGION FOR THE NEXT 10
DAYS...INCLUDING THE GREEN RIVER. ALBRECHT/FELTON
&&
.AVIATION...A WEAK...UPPER TROF PRESENTLY OVER WRN WA WILL MOVE INTO
ERN WA LATE TODAY OR THIS EVENING. LIGHT AND VARIABLE FLOW ALOFT
WILL BECOME LIGHT WLY. CONTINUED WEAK...LOW LEVEL OFFSHORE FLOW.
MEANWHILE...CLOUDS BLANKETED MUCH OF THE AREA THIS MORNING. THE
EXCEPTION WAS THE COAST WHERE CLEARING HAD TAKEN PLACE. EXPECT CIGS
TO GRADUALLY LIFT OVER THE CLOUDY REGION THRU THIS AFTERNOON. THE
AREAS OF LIGHT PRECIP AND FOG SHOULD DISSIPATE BY EARLY THIS
AFTERNOON.
KSEA...CIGS SHOULD GENERALLY BE IN THE 4-6K FT RANGE TODAY. THERE
MAY BE A BRIEF PERIOD OF CIGS NEAR 1K FT THIS MORNING. OTHERWISE...
THE RISK OF -RA WILL CONTINUE TO DIMINISH THIS MORNING...WITH DRY
CONDITIONS LIKELY THIS AFTERNOON. THE LOWER CLOUD DECK WILL BECOME
SCATTERED BY 0300 UTC MON...WITH HIGH CLOUDS...CIGS AT OR ABOVE 15K
FT ANTICIPATED OVERNIGHT. HOWEVER...WITH LINGERING LOW LEVEL
MOISTURE AND WEAK SFC PRES GRADIENTS...THERE WILL BE THE POTENTIAL
FOR STRATUS AND/OR FOG DEVELOPMENT LATER TONIGHT.
&&
.MARINE...WEAK OFFSHORE FLOW WILL CONTINUE THROUGH MON DUE TO LOWER
PRES OVER THE ERN PAC AND HIGHER PRES INLAND. EXPECT A WEAKENING
OCCLUDED FRONT TO DISSIPATE AS IT APPROACHES THE COASTAL WATERS LATE
MON. THE FLOW MAY BECOME LIGHT ONSHORE ON TUE AS HIGHER PRES BUILDS
OVER THE ERN PAC.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IS IN EFFECT FOR
THE WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA AND THE COASTAL
WATERS.
.SMALL CRAFT ADVISORY GRAYS HARBOR FOR ROUGH BAR CONDITIONS.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE)
000
FXUS66 KSEW 071152
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
350 AM PST SUN FEB 7 2010
.SYNOPSIS...A DISSIPATING FRONTAL SYSTEM WILL CONTINUE TO BRING
LIGHT SHOWERS TO THE AREA ESPECIALLY OVER THE NORTH INTERIOR THIS
MORNING. HIGH PRESSURE AT THE SURFACE AND ALOFT OVER THE INLAND
NORTHWEST WILL GIVE DRY CONDITIONS AND LIGHT OFFSHORE FLOW LATER
SUNDAY INTO MONDAY. ANOTHER SPLITTING FRONT WILL AFFECT MAINLY THE
COASTAL AREAS MONDAY NIGHT. SLIGHTLY STRONGER SYSTEMS WILL AFFECT
THE REGION LATER IN THE WEEK TO COME...GIVING LIGHT RAIN AT TIMES
AND BREEZY CONDITIONS. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH
THE WEEK.
&&
.SHORT TERM...UPPER LEVEL TROUGH REMAINING OVER WESTERN WASHINGTON
THIS MORNING BEFORE DISSIPATING THIS AFTERNOON. RAIN ENDED OVER THE
SOUTHWEST INTERIOR AROUND 07Z BUT HAS CONTINUED BETWEEN THE SOUTHERN
PUGET SOUND TO AROUND WHIDBEY ISLAND THOUGH THE EARLY MORNING HOURS.
THE SYSTEM IS WEAKENING WITH CLOUD TOPS BEGINNING TO WARM IN THE
LAST COUPLE OF HOURS. EXPECT THE RAIN TO SPREAD NORTH IN THE NEXT
COUPLE OF HOURS AND HAVE UPPED THE POPS TO LIKELY FOR THE NORTHWEST
INTERIOR. UPPER LEVEL TROUGH SLOWLY MOVING EAST THIS AFTERNOON WITH
SHOWER ACTIVITY ENDING OVER THE AREA BY LATE MORNING. WEAK UPPER
LEVEL RIDGE BUILDING OVER WESTERN WASHINGTON TONIGHT. LOW LEVEL LOW
GOING WEAKLY OFFSHORE AS THE NEXT SPLITTING SYSTEM APPROACHES THE
COAST. THIS SHOULD HELP DRY OUT THE LOWER LEVELS OVERNIGHT INTO
MONDAY MORNING. FRONT HAS A HARD TIME MOVING EASTWARD ON MONDAY AS
THE UPPER LEVEL LOW ASSOCIATED WITH THE FRONT STARTS TO DIVE
SOUTHEAST TO THE WEST OF 130W. LOW LEVEL FLOW REMAINING OFFSHORE ON
MONDAY RESULTING IN ANOTHER DAY OF ABOVE NORMAL HIGH TEMPERATURES
FOR WESTERN WASHINGTON. THE LOW WILL CONTINUE TO DROP SOUTHEAST AND
BY 12Z TUE WILL BE SOMEWHERE JUST OFF THE SOUTHERN OREGON COAST.
THERE STILL IS A CHANCE THE FRONT COULD GET FAR ENOUGH EAST TO BRING
SOME VERY LIGHT RAIN PRECIPITATION TO THE WESTERN WASHINGTON
INTERIOR MONDAY NIGHT BEFORE THE PRECIPITATION MOVES SOUTH WITH THE
LOW. WILL STAY WITH THE CHANCE POPS AT THAT TIME. UPPER LEVEL LOW
CONTINUING TO MOVE SOUTHEAST ON TUESDAY LEAVING WESTERN WASHINGTON
DRY. SURFACE GRADIENTS FLAT ON TUESDAY SO EVEN THOUGH THERE WILL BE
LESS CLOUD COVER WILL GO FOR SLIGHTLY LOWER MAX TEMPS TUESDAY.
.LONG TERM...GFS AND ECMWF STILL NOT SHOWING MUCH CONSISTENCY ON THE
00Z RUN. THE CANADIAN MODEL HAS BEEN CONSISTENT FOR THE LAST FOUR
NIGHT WITH ITS SOLUTION AND THE FORECASTS WILL TREND TOWARD THAT
MODEL THIS MORNING. UPPER LEVEL PATTERN REMAINING SPLIT OFF THE
COAST THROUGH LATE THURSDAY. FLOW ALOFT BECOMING MORE CONSOLIDATED
BEGINNING FRIDAY WHICH WILL ALLOW SOME STRONGER WEATHER SYSTEMS TO
REACH THE AREA. CONFIDENCE STILL NOT RUNNING VERY HIGH WITH THE
VARIABILITY IN THE EXTENDED SOLUTIONS. FOR NOW WILL STAY WITH THE
CHANCE POPS FOR WEDNESDAY THROUGH THURSDAY NIGHT WHICH IS IN LINE
WITH THE CANADIAN SOLUTION. THE ECMWF AND THE GFS BOTH BRING A
SPLITTING BUT STILL INTACT SYSTEM INTO WESTERN WASHINGTON ON
THURSDAY. WILL UP THE POPS TO LIKELY FOR FRIDAY AND SATURDAY WITH
LESS SPLIT IN THE UPPER LEVEL FLOW OFFSHORE. TEMPERATURES WILL
REMAIN ABOVE NORMAL THROUGH THE PERIOD. FELTON
&&
.HYDROLOGY...JUST LIGHT PRECIPITATION EXPECTED OVER WESTERN EARLY
TODAY. THE PERIOD FROM SUNDAY AFTERNOON THROUGH WEDNESDAY SHOULD BE
PREDOMINANTLY DRY. BEYOND WEDNESDAY WEATHER SYSTEMS ARRIVING IN THE
AREA LOOK TO BE A LITTLE STRONGER VERSUS THE SYSTEMS MOVING THROUGH
IN THE PAST FEW DAYS. EVEN WITH THE STRONGER SYSTEMS...A SPLIT IN
THE UPPER LEVEL FLOW OFF THE COAST WILL REMAIN...AT LEAST THROUGH
THURSDAY. THE ECMWF BRINGS A COUPLE OF STRONGER AND WETTER SYSTEMS
INTO WESTERN WASHINGTON LATER THURSDAY AND FRIDAY. THE OTHER
EXTENDED MODELS ARE WEAKER AND HAVE LESS PRECIPITATION. FROM
SATURDAY ONWARD THE FLOW ALOFT BECOMES SPLIT ONCE AGAIN LEAVING ONLY
WEAKENING SYSTEMS WITHOUT HYDROLOGICALLY SIGNIFICANT RAINFALL TO
PASS THROUGH THE AREA. THE FLOOD THREAT WILL REMAIN LOW OVER THE
REGION FOR THE NEXT 10 DAYS...INCLUDING THE GREEN RIVER. FELTON
&&
.AVIATION...THE WEAK UPPER TROF AND PERSISTENT WEATHER SYSTEM GIVING
AREAS OF LIGHT RAIN EARLY THIS MORNING HAS MOISTENED UP THE LOW
LEVEL AIR MASS. PRESSURE GRADIENTS ARE VERY LIGHT AND AIR MASS IS
STABLE. LIGHT WINDS ALOFT. TIME HEIGHT RH CROSS SECTION KEEPS THE
AIR MASS MOIST ENUF SO THAT IF CIGS BREAK UP LATER THIS AFTERNOON
AND EVENING LOW STRATUS AND FOG ARE LIKELY TONITE AND MON
MORNING...AFTER WHICH MID AND HIGH CLOUDS INCREASE MONDAY AS THE LOW
LEVELS DRY OUT. 19
KSEA...THE AREAS OF LIGHT RAIN SHOULD DRY UP AROUND DAYBREAK...WITH
ONLY VERY SLOW IMPROVEMENT THRU THE DAY. WITH A MOIST LOW LEVEL AIR
MASS AND LIGHT WINDS LOW STRATUS SHOULD DEVELOP AGAIN TNGT. VRB04KT
WIND.
&&
.MARINE...LIGHT GRADIENTS...A WEAK FRONT BREAKS UP JUST OFFSHORE MON
AFTERNOON. STRONGER SYSTEMS AFTER THE MIDDLE OF NEXT WEEK. SWELL IS
ARND 10 FEET TODAY AND SHOULD STAY ARND THERE THRU TNGT FOR SMALL
CRAFT ADVISORY FOR HAZARDOUS SEAS AND ROUGH BAR CONDITIONS.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IN EFFECT FOR THE
COASTAL WATERS THRU SUNDAY NIGHT.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT THRU SUNDAY NIGHT.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE)
000
FXUS66 KSEW 070519
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
918 PM PST SAT FEB 6 2010
.SYNOPSIS...A DISSIPATING FRONTAL SYSTEM WAS BRINGING SPRINKLES AND
LIGHT RAIN TO MUCH OF WESTERN WASHINGTON ON SATURDAY EVENING. HIGH
PRESSURE AT THE SURFACE AND ALOFT OVER THE INLAND NORTHWEST WILL
GIVE DRY CONDITIONS AND LIGHT OFFSHORE FLOW LATER SUNDAY INTO
MONDAY. ANOTHER SPLITTING FRONT WILL AFFECT MAINLY THE COASTAL AREAS
MONDAY NIGHT. SLIGHTLY STRONGER SYSTEMS WILL AFFECT THE REGION LATER
IN THE WEEK TO COME...GIVING LIGHT RAIN AT TIMES AND BREEZY
CONDITIONS. IN ADDITION...TEMPERATURES WILL REMAIN ABOVE NORMAL.
&&
.SHORT TERM...A WEAKENING MID-LEVEL TROUGH AXIS WAS JUST OFFSHORE
THIS EVENING. A ZONE OF SOUTHERLY MID-LEVEL FLOW IN ADVANCE OF THE
TROUGH WAS ADVECTING A BAND OF MOISTURE NORTHWARD...BRINGING A
HEALTHY COVERAGE OF SPRINKLES AND LIGHT RAIN TO ALL BUT THE NERN
1/3RD OF THE FCST AREA. ALREADY UPDATED THE FORECASTS AROUND 7 PM TO
BOOST POPS FOR TONIGHT HIGHER UP IN THE CHANCE CATEGORY. EVEN THAT
MAY BE UNDER-DONE IN THE TRUE SENSE OF A POP REPRESENTING ANY
MEASURABLE PRECIP...BUT RAINFALL AMOUNTS ARE LIGHT...GENERALLY
1/10TH OF AN INCH OR LESS.
ANY LIFT WITH THE DISSIPATING TROUGH WILL BE GONE BY LATE SUNDAY
MORNING. SUNDAY AFTERNOON WILL BE DRY FOR THE VAST MAJORITY OF
LOCATIONS. NOT NECESSARILY EXPECTING A LOT OF SUNSHINE...BUT
REMAINING CLOUD LAYERS SHOULD BE PRETTY THIN AND LET AT LEAST
FILTERED SUNSHINE THROUGH.
A PIECE OF THE LARGE-SCALE UPPER TROUGH CURRENTLY OUT AROUND 155W
WILL BREAK OFF AND HEAD SOUTHEAST ON MONDAY. THIS BREAKOFF SYSTEM
WILL CROSS 130W WHILE WEST OF OREGON AND EVENTUALLY REACH THE COAST
OF NRN CALIFORNIA. THIS WILL SIMPLY INCREASE OFFSHORE FLOW OVER WRN
WA A LITTLE BIT AND INCREASE OUR HIGH CLOUD COVERAGE. OTHERWISE...
EXPECTING MON AND TUE TO BE DRY DAYS. HANER
.LONG TERM...FROM PREVIOUS DISCUSSION...THE PATTERN REMAINS SPLIT
THROUGH THE LONG TERM. BUT GLOBAL MODELS ARE ALL INSISTING THAT THE
RIDGE OVER THE INLAND NW WILL WEAKEN SOMEWHAT AND THAT INCOMING
SYSTEMS WILL BE STRONGER THAN THEY HAVE BEEN OF LATE. TIMING OF
INDIVIDUAL FEATURES IS UNCERTAIN...SO WILL CONTINUE WITH A BROAD
BRUSH FORECAST- BUT WITH HIGHER POPS AND SLIGHTLY LOWER DIURNAL
SPREAD TO THE TEMPERATURES. ALBRECHT
&&
.HYDROLOGY...JUST LIGHT PRECIPITATION EXPECTED OVER WESTERN
WASHINGTON TONIGHT AND EARLY SUNDAY. THE PERIOD FROM SUNDAY
AFTERNOON THROUGH WEDNESDAY SHOULD BE PREDOMINANTLY DRY. BEYOND
WEDNESDAY WEATHER SYSTEMS ARRIVING IN THE AREA LOOK TO BE A LITTLE
STRONGER VERSUS THE SYSTEMS MOVING THROUGH IN THE PAST FEW DAYS.
EVEN WITH THE STRONGER SYSTEMS...A SPLIT IN THE UPPER LEVEL FLOW OFF
THE COAST WILL REMAIN...WHICH WILL WEAKEN THE SYSTEMS AS THEY MOVE
INTO WESTERN WASHINGTON. THE FLOOD THREAT WILL REMAIN LOW OVER THE
REGION FOR THE NEXT 10 DAYS...INCLUDING THE GREEN RIVER. HANER
&&
.AVIATION...A RATHER WEAK UPPER TROF OVER WRN WA...BUT AREAS OF
LIGHT RAIN HAVE DEVELOPED FROM THIS SYSTEM. THIS IS GOING TO MOISTEN
THE LOWER LEVEL AIR MASS...AND WITH VERY LIGHT GRADIENTS AND NO
DOWNSLOPE DRYING OFF THE CASCADES CONDITIONS SHUD GRADUALLY
DETERIORATE. RH CROSS SECTION MAKES IT LOOK LIKE IT WILL BE A MURKY
MORNING SUNDAY. LIGHT SLY WIND ALF. UPPER TROF DSIPTS OVER WA SUN. 19
KSEA...CURRENT TAF IS NOT FCSTG CIGS TO DROP BLO 040...AND THEN
IMPROVEMENT AFTER DAYBREAK AS THE SYSTEM BREAKS UP. BUT THE CROSS
SECTION OF RH THRU SUN MORNING LOOKS AWFULLY MOIST AND WITH ONLY
VERY LIGHT WINDS I AM NOT OPTIMISTIC THAT THE TAF WILL HOLD UP...SO
THE 06Z TAF WILL BE A FCST FOR A MURKIER SITN THRU SUN MORNING. 19
&&
.MARINE...LIGHT GRADIENTS...A WEAK FRONT BREAKS UP JUST OFFSHORE MON
AFTERNOON. STRONGER SYSTEMS AFTER THE MIDDLE OF NEXT WEEK. SWELL IS
ARND 10 FEET TONIGHT AND SHOULD NOT SUBSIDE SUNDAY SO SMALL CRAFT
FOR HAZ SEAS.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IN EFFECT FOR THE
COASTAL WATERS THRU SUNDAY NIGHT.
A SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
IS IN EFFECT THRU SUNDAY NIGHT.
$$
WWW.WEATHER.GOV/SEATTLE
FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE)
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