Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 251005
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
305 AM PDT WED MAR 25 2015

.SYNOPSIS...A WARM FRONT WILL BRING PERIODS OF RAIN TO WESTERN
WASHINGTON TODAY. RAIN WILL DECREASE THIS EVENING AS THE WARM FRONT
MOVES NORTH OVER BRITISH COLUMBIA. AN UPPER LEVEL RIDGE WILL BRING
WARM AND DRY CONDITIONS THURSDAY WITH PARTLY SUNNY SKIES IN THE
AFTERNOON. A COLD FRONT WILL CROSS THE AREA FRIDAY EVENING. SOMEWHAT
MOIST WEST FLOW ALOFT WILL BRING A CHANCE OF LIGHT RAIN TO THE COAST
AND NORTH INTERIOR THIS WEEKEND WITH DRY CONDITIONS ELSEWHERE. SKIES
WILL BE PARTLY TO MOSTLY CLOUDY.

&&

.SHORT TERM...A BROAD LOW AMPLITUDE UPPER LEVEL RIDGE HAS MOVED OVER
130W THIS MORNING. SIGNIFICANT WARM ADVECTION PUSHING UNDER THE
RIDGE HAS BROUGHT RAIN TO ALL OF W WA OVERNIGHT. MODELS KEEP THE
RAIN GOING ALL DAY TODAY WITH ABOUT AN INCH OF RAIN OVER MUCH OF THE
COAST...AND 0.10 TO 0.60 OF AN INCH OVER THE LOWLANDS. SNOW LEVELS
AROUND 3500-4000 FEET THIS MORNING WILL RISE TO 6500 FEET LATE THIS
AFTERNOON AS WARMER AIR MOVES OVER THE REGION.

THE MODELS REMAIN CONSISTENT WITH THE TIMING OF THE WARM FRONT
TONIGHT...ALLOWING RAIN TO DIMINISH FROM THE S THIS EVENING AS THE
BUILDING UPPER LEVEL RIDGE PUSHES THE WARM FRONT N OVER BRITISH
COLUMBIA.

THURSDAY SHOULD BE DRY AS W WA REMAINS UNDER THE UPPER LEVEL RIDGE
AXIS...BUT CLOUDS WILL BE SLOWER TO DIMINISH FROM THE S. MOSTLY
CLOUDY SKIES ARE STILL EXPECTED THURSDAY MORNING...BUT THE LOWER AIR
MASS WILL DRY ENOUGH FROM PUGET SOUND SOUTHWARD FOR A PARTLY SUNNY
FORECAST THURSDAY AFTERNOON. THE MODELS ARE STILL KEEPING A LOT OF
HIGH LEVEL MOISTURE OVER THE AREA IN THE AFTERNOON...HENCE BACKING
OFF TO A PARTLY SUNNY FORECAST. ALL THE WARM ADVECTION COMBINED WITH
A BIT MORE SUNSHINE WILL ALLOW MAX TEMPS TO CLIMB WELL INTO THE 60S.
SOME LOWER 70S ARE POSSIBLE OVER THE SW INTERIOR.

THE MODELS ARE NOW IN GOOD AGREEMENT THAT AN UPPER LEVEL SHORTWAVE
TROUGH WILL DRIVE A FAST MOVING COLD FRONT ACROSS W WA FRIDAY
EVENING. RAIN AHEAD OF THE COLD FRONT WILL PROBABLY REACH THE N
COAST LATE FRIDAY MORNING...THEN SPREAD ACROSS AREAS W OF PUGET
SOUND IN THE AFTERNOON. THE FRONT WILL ZIP E FRIDAY EVENING AND
SHOULD BE OVER THE CASCADES BY 06Z. QPF IS EXPECTED TO RANGE FROM UP
TO A COUPLE TENTHS OVER THE INTERIOR TO A HALF INCH OVER THE N
COAST. ONSHORE FLOW WITH AND BEHIND THE FRONT SHOULD PRODUCE A PUGET
SOUND CONVERGENCE ZONE FRIDAY NIGHT. OTHER THAN THE CONVERGENCE ZONE
CONTINUING BEHIND THE FRONT...SHOWERS OVER THE LOWLANDS SHOULD BE
SPARSE. KAM

.LONG TERM...THE GFS...ECMWF AND CANADIAN ALL MAINTAIN A BROAD FLAT
UPPER LEVEL RIDGE OVER W WA THROUGH THIS WEEKEND. FLOW ALOFT WILL BE
WESTERLY. ALL MODELS SHOW A WARM FRONT MOVING NE ACROSS VANCOUVER
ISLAND SATURDAY AFTERNOON...BRUSHING THE WA COAST AND N INTERIOR IN
THE PROCESS. THE REST OF W WA SHOULD REMAIN DRY WITH EVEN PARTLY
SUNNY SKIES AT TIMES. THE WEAK WARM ADVECTION BRUSHING THE NW PART
WILL CONTINUE THROUGH SUNDAY. ANY RAIN THAT FALLS SHOULD BE
LIGHT...BUT WITH GOOD MODELS CONSENSUS...A CHANCE OF RAIN HAD TO BE
PUT BACK IN THE FORECAST. THE MODELS ARE IN LOOSER AGREEMENT FOR
MONDAY AND TUESDAY WHEN THE ASSOCIATED COLD FRONT WILL MOVE ACROSS W
WA. KAM

&&

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

&&

.AVIATION...AN UPPER RIDGE WILL MOVE OVER WESTERN WASHINGTON TODAY
AND TONIGHT WITH WESTERLY FLOW ALOFT. A WARM FRONT WILL MOVE INTO
THE AREA TODAY...LIFTING NORTH OF THE AREA TONIGHT. AIR MASS STABLE
AND MOIST AT ALL LEVELS.

KSEA...LOW CLOUDS WILL PREVAIL MOST OF TODAY WITH CEILINGS GENERALLY
2000-3000 FEET. CEILINGS SHOULD IMPROVE A BIT TONIGHT AS THE WARM
FRONT LIFTS NORTH OF THE AREA. SOUTHEAST WIND 5-10 KNOTS WILL BECOME
SOUTH 10-15 KNOTS THIS AFTERNOON...THEN DIMINISH THIS EVENING.
SCHNEIDER

&&

.MARINE...A WARM FRONT WILL MOVE THROUGH THE AREA TODAY...BRINGING
SMALL CRAFT ADVISORY SOUTHERLY WINDS TO MOST WATERS. WEAK HIGH
PRESSURE WILL MOVE OVER WESTERN WASHINGTON TONIGHT AND THURSDAY. A
WEAK COLD FRONT WILL CROSS THE AREA FRIDAY AFTERNOON OR EVENING.
HIGH PRESSURE WILL REBUILD OVER THE AREA SATURDAY AND SUNDAY.
SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL WATERS EXCEPT THE
     CENTRAL STRAIT OF JUAN DE FUCA.

&&

$$

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