Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 201618
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PDT MON APR 20 2015

.SYNOPSIS...A WARM SUNNY DAY TODAY WILL BE FOLLOWED BY COOL MARINE
AIR PUSHING INTO WESTERN WASHINGTON TONIGHT AND TUESDAY. AN UPPER
TROUGH WILL BRING INCREASING SHOWERS TO THE AREA TUESDAY AND
WEDNESDAY. A FRONT WILL ARRIVE LATER THURSDAY. STRONGER FRONTS ARE
LIKELY TO ARRIVE NEXT WEEKEND.

&&

.SHORT TERM...THE RIDGE IS WEAKENING AND WILL MOVE SLOWLY INLAND
THROUGH TUESDAY. A STRETCHED OUT UPPER TROUGH CROSSES 130W TODAY...
SPLITS APART SOME MORE...AND THEN THE NORTHERN PORTION OF THE TROUGH
MOVES OVER WESTERN WA TUESDAY NIGHT. THE TROUGH EVOLVES INTO MORE OF
A CLOSED UPPER LOW WEDNESDAY...MOVING TO EASTERN WA BY WEDNESDAY
EVENING. MEANWHILE...ANOTHER UPPER TROUGH MOVES INTO THE NE PACIFIC
AND AN ASSOCIATED COLD FRONT REACHES WRN WA AROUND THU AFTERNOON.

.LONG TERM...AFTER THE COLD FRONT AND ITS ASSOCIATED UPPER TROUGH
MOVE INLAND THU NITE THERE WILL BE A BRIEF PERIOD OF WEAK RIDGING
THROUGH FRI NITE. SEVERAL FRONTAL WAVES ARE LIKELY FROM NEXT WEEKEND
INTO THE LAST FEW DAYS OF APRIL WHILE A LARGE UPPER TROUGH TAKES
UP RESIDENCE IN THE NE PACIFIC.

&&

.AVIATION...AN UPPER LEVEL RIDGE OVER THE PACIFIC NORTHWEST WILL
LEAD TO DRY AND STABLE WEATHER ACROSS WESTERN WASHINGTON TODAY. THE
FLOW ALOFT IS WESTERLY. VFR CONDITIONS ARE EXPECTED. SKIES WILL
REMAIN MOSTLY CLEAR WITH JUST FEW-SCT CIRRUS ALOFT. A MARINE PUSH
WILL BRING LOW CLOUDS TO THE COAST THIS EVENING WITH STRATUS MOVING
INTO THE INTERIOR EARLY TUESDAY...WITH MVFR TO IFR CEILINGS LIKELY.

KSEA...NORTH WIND TO 10 KT. LOW LEVEL MARINE CLOUDS WILL PUSH INLAND
LATE TONIGHT OR EARLY TUESDAY MORNING WITH MVFR TO IFR CEILINGS
LIKELY.   MCDONNAL

&&

.MARINE...ONSHORE FLOW WILL STRENGTHEN TODAY AND TONIGHT AS LOW
PRESSURE ALONG THE COAST SHIFTS INLAND. SMALL CRAFT ADVISORY
WESTERLIES ARE LIKELY IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE
FUCA...ADMIRALTY INLET...AND NORTHERN INLAND WATERS.

ONSHORE FLOW WILL INCREASE FURTHER ON TUESDAY AS A COLD FRONT MOVES
INLAND...THEN CONTINUE THROUGH WEDNESDAY. WESTERLIES GALES ARE VERY
LIKELY IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA TUESDAY
NIGHT...AND LIKELY IN THE NORTHWEST PART OF THE COASTAL WATERS AS
WELL. A GALE WATCH HAS BEEN ISSUED FOR THESE ZONES.

ANOTHER COLD FRONT WILL CROSS THE AREA LATE WEDNESDAY NIGHT OR
THURSDAY.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE
       FUCA...ADMIRALTY INLET...NORTHERN INLAND WATERS.
    .GALE WATCH COASTAL WATERS ZONES 150 170 173...CENTRAL AND
       EASTERN STRAIT.

&&

$$

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





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