Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 251740
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
940 AM PST TUE NOV 25 2014

.SYNOPSIS...A WARM FRONT WILL BRING RAINY BREEZY WEATHER TO WESTERN
WASHINGTON TODAY...WITH HEAVY RAIN IN THE MOUNTAINS. AFTER A
RELATIVE LULL TONIGHT AND WEDNESDAY...ANOTHER FRONT WILL BRING MORE
RAINY WINDY WEATHER WEDNESDAY NIGHT AND THANKSGIVING. RAIN WILL
DECREASE ON FRIDAY AS A COLD FRONT MOVES SOUTHEAST ACROSS THE AREA.
COOLER DRIER WEATHER IS EXPECTED FOR THIS WEEKEND.

&&

.SHORT TERM...A WARM FRONT IS DRAPED OVER W WA THIS MORNING. LIGHT
RAIN AT TIMES IS EXPECTED OVER THE LOWLANDS WITH LOCALIZED HEAVY
RAIN OVER THE CASCADES. SO FAR A STRONG LOW LEVEL WESTERLY JET
PASSING S OF THE OLYMPICS HAS BEEN SLAMMING INTO THE CASCADES S OF
SNOQUALMIE PASS...PRODUCING HEAVY RAIN. 24 HOUR PRECIP OVER THE
CASCADES FROM STEVENS PASS SOUTHWARD HAS RANGED FROM 2-5 INCHES WITH
THE 5 INCH BULLSEYES AROUND MT RAINIER.

THE WARM FRONT EXTENDS E FROM A LARGE UPPER LEVEL LOW OFFSHORE NEAR
40N/150W...ACROSS A BROAD FLAT UPPER LEVEL RIDGE CENTERED JUST
OFFSHORE ALONG ROUGHLY 130W. MODELS STILL AGREE ON SHIFTING THE WARM
FRONT NORTH TODAY...EVENTUALLY STALLING IT ALONG THE CANADIAN BORDER
THIS EVENING. HRRR MODEL SHOWS THE HEAVY RAIN OVER THE CENTRAL
DIMINISHING EARLY THIS AFTERNOON AROUND 21Z AS THE WARM FRONT SHIFTS
N. MODELS SEEM TO MOVE THE FRONT QUICK ENOUGH SO THAT MOST OF THE
REST OF THE CASCADES DO NOT GET AS MUCH HEAVY RAIN AS PREVIOUSLY
EXPECTED. HOWEVER THE FRONT IS CLOSE ENOUGH TO THE BORDER SO THAT
HEAVY RAIN COULD CONTINUE OVER FAR N CASCADES TONIGHT.

OVER THE LOWLANDS...RAIN WILL DIMINISH FROM S TO N THIS AFTERNOON AS
THE WARM FRONT MOVES N. RAIN WILL PROBABLY CONTINUE UP AROUND
BELLINGHAM WITH THE WARM FRONT STILL IN THE VICINITY.

A COLD FRONT ORIGINATING FROM THE OFFSHORE LOW IS STILL FORECAST TO
MOVE ACROSS W WA WEDNESDAY NIGHT. SW FLOW ALOFT WILL INCREASE AHEAD
OF THE FRONT AND CONTINUE BEHIND IT INTO THURSDAY NIGHT...UNTIL THE
LAST COLD FRONT MOVING S DOWN THE B.C. COAST FINALLY CROSSES THE
AREA FRIDAY MORNING. THE STRONG SW FLOW ALOFT WILL PRODUCE MORE
HEAVY RAIN OVER THE N CASCADES AND OVER THE OLYMPICS. THE LOWLANDS
WILL GET RAIN...BUT PARTS OF THE PUGET SOUND REGION WILL BE SHADOWED
BY THE OLYMPICS AT TIMES.

ALL THE WARM ADVECTION THE NEXT COUPLE OF DAYS WILL KEEP
TEMPERATURES MILD WITH LOWS NEAR 50 AND HIGHS IN THE MID 50S. WINDS
WILL BE BREEZY AT TIMES...PARTICULARLY ALONG THE COAST AND OVER THE
N INTERIOR. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 3 AM AFD...PRECIPITATION
OVER WESTERN WASHINGTON SHOULD DECREASE ON FRIDAY...IN THE WAKE OF
THE FRONT THAT DIGS THROUGH THE AREA THURSDAY NIGHT. MODELS HAVE
COME INTO FAIRLY STRONG AGREEMENT THAT AN UPPER TROUGH WILL DIG INTO
THE AREA FROM THE NORTHWEST FRIDAY NIGHT AND SATURDAY...WHILE
SURFACE HIGH PRESSURE OVER SOUTHERN BRITISH COLUMBIA PRODUCES
NORTHEAST PRESSURE GRADIENTS. THE WEEKEND WILL BE QUITE COOL WITH
LOWS IN THE MID 20S TO LOWER 30S AND HIGHS IN THE MID 30S TO MID
40S. THE DAYS SHOULD BE AT LEAST PARTLY SUNNY. WE WILL KEEP A
LOW-END CHANCE OF A SHOWER IN THE FORECAST FOR NOW...BUT ANY
PRECIPITATION WOULD BE VERY LIGHT. IT LOOKS LIKE THE COOL DRY SPELL
WILL BE SHORT LIVED...WITH ANOTHER FRONTAL SYSTEM LIFTING INTO
WESTERN WASHINGTON FROM THE SOUTHWEST SUNDAY NIGHT OR MONDAY.
MCDONNAL

&&

.HYDROLOGY...STRONG LOW LEVEL W FLOW ALOFT HAS DROPPED 2 TO 5 INCHES
OF RAIN OVER THE CENTRAL CASCADES FROM ABOUT STEVENS PASS
SOUTHWARD...WITH THE HEAVIEST AMOUNTS OVER THE MT RAINIER AREA.
SEVERAL FLOOD WARNING HAVE ALREADY BEEN ISSUED...AND A FLOOD WATCH
CONTINUES FOR THE CASCADES...INCLUDING THE COWLITZ...PUYALLUP NEAR
ORTING...SNOQUALMIE... TOLT...SKYKOMISH...SNOHOMISH...
STILLAGUAMISH...AND NOOKSACK RIVERS.


THE HEAVY RAIN WILL CONTINUE THROUGH EARLY THIS AFTERNOON
PARTICULARLY OVER THE MT RAINIER AREA. RAIN WILL DIMINISH THERE AS
THE WARM FRONT OVER THE AREA SHIFTS N...REACHING THE CANADIAN BORDER
EARLY THIS EVENING. MODELS APPEAR TO MOVE THE FRONT FAST ENOUGH SO
THAT ONLY MODERATE RAIN WILL FALL OVER THE NORTH CASCADES TODAY.

THE WARM FRONT WILL STALL ALONG THE CANADIAN BORDER TONIGHT WHICH
COULD ALLOW MODERATE RAIN TO CONTINUE OVER THE N CASCADES IN WHATCOM
AND SKAGIT COUNTY TONIGHT...WITH ANOTHER 0.75-1.50 INCHES POSSIBLE
FROM 03Z-15Z. SNOW LEVELS WILL REMAIN HIGH...FROM ROUGHLY 6000 TO
8000 FEET TONIGHT AND WEDNESDAY...LOWERING TO 5000-6000 FEET
THURSDAY AFTERNOON.

THERE WILL BE MORE OF A LULL IN RAIN ON WEDNESDAY AHEAD OF AN
APPROACHING COLD FRONT. STRONG LOW LEVEL SW FLOW ALOFT WILL DEVELOP
WEDNESDAY EVENING AHEAD OF THE COLD FRONT AND CONTINUE BEHIND THE
FRONT THROUGH THURSDAY AFTERNOON OR EVENING. THE SW DIRECTION SHOULD
PUT THE HEAVIEST RAIN OVER THE OLYMPICS AND N CASCADES WITH ANOTHER
3 TO 5 INCHES POSSIBLE IN THOSE AREAS. KAM

&&

.AVIATION...MODERATE WESTERLY FLOW ALOFT. A FRONT OVER THE AREA WILL
GIVE LOW MVFR TO IFR CEILINGS AND VISIBILITIES IN RAIN TO MOST
TERMINALS TODAY. THE FRONT WILL MOVE NORTH LATE THIS AFTERNOON AND
WILL REACH THE CANADIAN BORDER TONIGHT. LIGHT WINDS AT THE SURFACE
WILL INCREASE TONIGHT BEHIND THE FRONT. SLIGHT IMPROVEMENT TO
VISIBILITIES AND CEILINGS CAN BE EXPECTED BEHIND THE FRONT.

KSEA...CEILINGS AROUND 005 WITH VISIBILITY 3-5SM IN -RA BR. THE
FRONT WILL MOVE NORTH ABOUT 00Z THIS AFTERNOON WITH VISIBILITY
RISING TO P6SM AND CIGS RISING TO 008-012. LIGHT WINDS WILL BECOME
SOUTHERLY 10-14KT BEHIND THE FRONT ABOUT 00Z. CHB

&&

.MARINE...A FRONT OVER THE AREA THIS MORNING WILL MOVE NORTH INTO
SOUTHERN BRITISH COLUMBIA LATE THIS AFTERNOON AND EVENING. SMALL
CRAFT ADVISORY WINDS ARE LIKELY ON THE COAST LATER TODAY AND
TONIGHT. WINDS WILL BE GENERALLY LIGHTER INLAND.

WINDS WILL INCREASE WEDNESDAY AS A COLD FRONT APPROACHES THE COAST.
AT LEAST SMALL CRAFT ADVISORY LEVEL WINDS ARE LIKELY OVER MOST
WATERS WITH GALES POSSIBLE ON THE COAST AND OVER EXPOSED INLAND
AREAS WEDNESDAY NIGHT. A GALE WATCH IS IN EFFECT FOR THE COAST...THE
STRAIT ENTRANCES...AND THE NORTHERN INLAND WATERS WEDNESDAY NIGHT.

ANOTHER COLD FRONT WILL MOVE THROUGH THE WATERS ON FRIDAY. THIS
FRONT WILL BE FOLLOWED BY STRONG FRASER OUTFLOW IN THE NORTHERN
INLAND WATERS AND MODERATE NORTHERLY WINDS OVER THE OTHER WATERS
LATER FRIDAY INTO SATURDAY. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH IN EFFECT FOR PORTIONS OF THE AREA.
PZ...SMALL CRAFT ADVISORY COAST AND WEST ENTRANCE.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH COAST...ENTRANCES...AND NORTHERN INLAND WATERS
     WEDNESDAY NIGHT.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









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