Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 251131
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST WED FEB 25 2015

.SYNOPSIS...SPOTTY LIGHT RAIN OVER PARTS OF WESTERN WASHINGTON THIS
MORNING WILL BECOME MORE WIDESPREAD THIS AFTERNOON AND EVENING AS A
WEAK SYSTEM MOVES INTO THE AREA LATER TODAY. A SHOWERY PATTERN WILL
PERSIST THROUGH FRIDAY...GIVING WAY TO DRY OFFSHORE FLOW SATURDAY
AND SUNDAY. A WETTER...AND COOLER PATTERN WILL RETURN EARLY NEXT
WEEK.

&&

.SHORT TERM...SPOTTY SHOWERS MAINLY ALONG THE COAST AND CENTRAL
INTERIOR THIS MORNING WILL FILL IN AS A RELATIVELY WEAK SYSTEM
APPROACHES THE AREA FROM THE WEST-NORTHWEST THIS AFTERNOON. MODELS
BRING LIGHT RAIN TO THE COAST WITH WARM AIR ADVECTION AROUND
MIDDAY...SPREADING IT INLAND DURING THE AFTERNOON. RAIN WILL
TRANSITION TO SHOWERS BY THURSDAY AS THE WARM FRONTAL WAVE GIVES WAY
TO THE UPPER LEVEL TROUGH. SHOWERS WILL LINGER THROUGH FRIDAY AS THE
TROUGH DIGS SE ACROSS THE AREA...BRINGING COLDER AIR ALOFT AND LOWER
SNOW LEVELS.

.LONG TERM...THE UPPER LEVEL RIDGE ALONG 140W WILL TIP INTO BRITISH
COLUMBIA SATURDAY AND SOUTH OVER WASHINGTON SATURDAY NIGHT AND
SUNDAY. LINGERING SHOWERS...MAINLY OVER THE CASCADES OF PIERCE AND
LEWIS COUNTIES SATURDAY MORNING WILL GIVE WAY TO DRY CONDITIONS AS
HIGH PRESSURE BUILDS OVER WESTERN WASHINGTON. A SECOND WEAK SYSTEM
WILL BRING RAIN MONDAY OR TUESDAY. MEDIUM RANGE MODELS DIFFER ON THE
TIMING AND STRENGTH OF THIS SYSTEM. THE ECMWF BRINGS A MORE
CONSOLIDATED SYSTEM SOUTH FROM BRITISH COLUMBIA EARLY MONDAY MORNING
AND RAIN TO MUCH OF THE AREA MONDAY. WHILE THE GFS BRINGS A MUCH
WEAKER...AND SLOWER FEATURE THROUGH LATER MONDAY EVENING PRODUCING
LITTLE MORE THAN SHOWERS OVER THE CASCADES MONDAY NIGHT. BOTH MODELS
DO AGREE ON COOLER TEMPERATURES FOR TUESDAY WITH SOME DEGREE OF
OUTFLOW VIA THE FRASER. HIGH TEMPERATURES REMAIN FORECAST TO REMAIN
MAINLY IN THE UPPER 40S THROUGH THE EARLY PART OF NEXT WEEK.

&&

.HYDROLOGY...FLOODING IS UNLIKELY THE NEXT 7 DAYS.

&&

.AVIATION...NORTHWEST FLOW ALOFT WITH LIGHT PRES GRADIENTS AT THE
SURFACE. THE AIR MASS IS STABLE WITH ABUNDANT LOW LEVEL MOISTURE
ACROSS THE AREA. A WEAK FRONTAL SYSTEM WILL MOVE ACROSS THE AREA
TONIGHT REACHING THE WASHINGTON COAST ABOUT 06Z AND MOVING THROUGH
THE INTERIOR LOWLANDS BY 12Z THU.

STRATUS BASES ARE AROUND 040 ACROSS THE INTERIOR EARLY THIS MORNING
WITH AREAS OF STRATUS WITH BASES AROUND 015-020 ALONG THE
COAST...AROUND THE STRAIT OF JUAN DE FUCA...AND IN THE SOUTHERN
PORTIONS OF THE PUGET SOUND LOWLANDS. VISIBILITIES ARE GENERALLY
P6SM...BUT ARE 2-4SM -RA BR IN LIGHT SHOWERS ALONG THE COAST AND
AROUND A WEAK PUGET SOUND CONVERGENCE ZONE AROUND KPAE. EXPECT
LITTLE CHANGE THROUGH ABOUT 20Z TODAY THEN SOME BRIEF IMPROVEMENT
THIS AFTERNOON TO P6SM SCT020 BKN040 AS A WEAK UPPER LEVEL RIDGE
TRAVERSES ACROSS THE AREA.

CONDITIONS ARE EXPECTED TO ONCE AGAIN DETERIORATE ABOUT 00Z THIS
AFTERNOON TO 3-5SM -RA BR OVC010-015 AS A WEAK FRONTAL SYSTEM MOVES
ACROSS THE AREA. ALBRECHT

KSEA...P6SM SCT-BKN015 BKN-OVC035-040 THIS MORNING. EXPECT SOME
IMPROVEMENT TO P6SM SCT020 BKN040 20Z-24Z FOLLOWED BY DETERIORATION
TO OVC010-015 WITH 3-5SM -RA BR 00Z THIS EVENING. WINDS WILL BE SLY
GENERALLY LESS THAN 6 KT. ALBRECHT

&&

.MARINE...EXPECT LIGHT ONSHORE PRES GRADIENTS TODAY. A WEAK COLD
FRONT WILL PUSH SE ACROSS THE WATERS TONIGHT INTO EARLY THU MORNING.
AT THIS TIME IT APPEARS THAT WINDS THROUGHOUT THE AREA WITH THE
INCOMING FRONT WILL REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA.

A WEAK 1012 MB LOW WILL DROP S OVER THE COASTAL WATERS LATE THU
NIGHT INTO FRI. PRES GRADIENTS ARE EXPECTED TO REMAIN LIGHT OVER THE
WATERS AS THE LOW PASSES SOUTHWARD ACROSS THE AREA.

HIGH PRES WILL DEVELOP OVER BRITISH COLUMBIA FRI INTO FRI NIGHT. THE
COMBINATION OF THE BUILDING HIGH AND THE SURFACE LOW DEPARTING TO
THE SOUTH OF THE AREA WILL RESULT IN STRONG NE FLOW OVER THE WATERS
FRI NIGHT INTO SAT WITH SMALL CRAFT ADVISORY CONDITIONS EXPECTED
EVERYWHERE EXCEPT IN ADMIRALTY INLET AND PUGET SOUND/HOOD CANAL.
GALE FORCE WINDS ARE POSSIBLE AROUND THE WEST ENTRANCE OF THE STRAIT
OF JUAN DE FUCA EARLY SATURDAY MORNING. PRES GRADIENTS WILL RELAX ON
SUN AS HIGH PRES MOVES OVER THE WATERS. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

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