Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 261010
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT SUN APR 26 2015

.SYNOPSIS...A WEAK WARM FRONT WILL CLIP WESTERN WASHINGTON TODAY AND
TONIGHT WITH RAIN MAINLY ALONG THE COAST. HIGH PRESSURE WILL BRING
WARMER AND DRIER WEATHER ON MONDAY. A PAIR OF FRONTS WILL CROSS THE
REGION TUESDAY AND WEDNESDAY FOR COOLER AND WETTER WEATHER. AN UPPER
LEVEL TROUGH WILL MAINTAIN A CHANCE OF SHOWERS THROUGH THE END OF
THE WEEK.

&&

.SHORT TERM...TEMPS DROPPED TO THE 30S TO LOWER 40S EARLY THIS
MORNING WITH THE SKIES CLEARING OUT. THERE IS SOME PATCHY FOG IN THE
SOUTHWEST INTERIOR AS WELL. BUT CLOUDS WILL INCREASE ACROSS WESTERN
WA TODAY AS A WARM FRONT MOVES IN. THIS IS A WEAK FRONT WITH LIGHT
PRECIP MAINLY AFFECTING THE OLYMPIC PENINSULA. THE WARM FRONT WILL
SHIFT NORTH INTO SOUTHERN B.C. TONIGHT AS AN UPPER LEVEL RIDGE
BUILDS OVER THE PAC NW. THERE IS A CHANCE OF RAIN IN THE INTERIOR
BUT PRECIP AMOUNTS WILL BE PATCHY AND LIGHT. IT WILL BE WARMER
OVERNIGHT WITH LOWS IN THE MID 40S TO LOWER 50S.

MONDAY WILL BE WARMER AND DRIER AS THE UPPER LEVEL RIDGE CONTINUES
TO BUILD OVER THE REGION. EXPECT MOSTLY SUNNY SKIES WITH HIGHS IN
THE 70S ACROSS THE INTERIOR...WITH 60S ALONG THE COAST. THE RIDGE
WILL EXIT EAST MONDAY NIGHT AS A TROUGH DIGS OFFSHORE.

LOOK FOR COOLER AND WETTER WEATHER TUESDAY AND WEDNESDAY. SHOWERS
WILL RETURN ON TUESDAY AS A COLD FRONT MOVES INLAND. ONSHORE FLOW
WILL INCREASE BEHIND THE FRONT TUESDAY AFTERNOON FOR BREEZY S/SW
WINDS. MODELS SHOW A PUGET SOUND CONVERGENCE FORMING OVER THE
CENTRAL SOUND...AND SHOWERS FROM THE PSCZ MAY LINGER THROUGH TUESDAY
NIGHT. ANOTHER COLD FRONT WILL CROSS THE AREA ON WEDNESDAY FOR
ANOTHER ROUND OF SHOWERS AND BREEZY WEATHER. EXPECT HIGHS IN THE MID
50S TO LOWER 60S EACH DAY. 33

.LONG TERM...OVERALL CONFIDENCE IN THE LONG RANGE FORECAST REMAINS
LOW. MODELS SHOW ZONAL FLOW THURSDAY AND FRIDAY. A TROUGH OVER B.C.
MAY CLIP WESTERN WA FOR A CHANCE OF SHOWERS EACH DAY. AFTER THAT THE
MODELS DISAGREE ON THE PATTERN THROUGH THE WEEKEND. THEREFORE WILL
MAINTAIN A FORECAST CLOSE TO SEASONAL NORMS. 33

&&

.AVIATION...TEMPORARY UPPER LEVEL RIDGE MOVING THROUGH WESTERN
WASHINGTON THIS MORNING. WEAKENING FRONT REACHING THE COAST LATE IN
THE DAY WITH THE FRONT DISSIPATING AS IT MOVES INLAND TONIGHT INTO
EARLY MONDAY MORNING. AIR MASS STABLE.

SATELLITE IMAGERY SHOWS HIGH CLOUDS OUT AHEAD OF THE FRONT HAVE
REACHED THE COAST AND WILL SPREAD INLAND OVER THE NEXT COUPLE OF
HOURS. PATCHY FOG OVER THE SOUTHWEST INTERIOR WILL ONLY LAST UNTIL
AROUND SUNRISE. INCREASING MID LEVEL CLOUDS LATER THIS MORNING WITH
THE CEILINGS LOWERING DOWN TO BETWEEN 5000-8000 FEET THIS
AFTERNOON. RAIN BEGINNING ALONG THE COAST IN THE MID TO LATE
AFTERNOON HOURS WITH THE RAIN HOLDING OFF OVER THE INTERIOR UNTIL
THE EVENING HOURS. CEILINGS LOWERING DOWN TO NEAR 4000 FEET WITH THE
ONSET OF THE PRECIPITATION. SOME MVFR CIGS ARE POSSIBLE ALONG THE
COAST THIS EVENING.

KSEA...INCREASING CLOUDS AOA 15000 FEET THIS MORNING. CEILINGS
LOWERING THIS AFTERNOON DOWN TO NEAR 7000 FEET BY 00Z MONDAY. CHANCE
OF RAIN IN THE EVENING HOURS WILL CEILINGS CONTINUING TO LOWER INTO
THE 4000-5000 FOOT RANGE. SOUTHERLY WINDS 4 TO 8 KNOTS. FELTON

&&

.MARINE...FLAT SURFACE GRADIENTS THIS MORNING WITH WEAK HIGH
PRESSURE ACROSS THE AREA. A WEAK FRONT WILL MOVE INTO THE COASTAL
WATERS LATER THIS AFTERNOON. THE FRONT WILL DISSIPATE LATER TONIGHT
AS IT MOVES INLAND. SOUTHERLY WINDS WILL PICK UP OVER THE COASTAL
WATERS IN ADVANCE OF THE FRONT WITH MID TO HIGH END SMALL CRAFT
ADVISORY WINDS ARE EXPECTED TODAY INTO TONIGHT. SOUTHERLY WINDS ARE
FORECASTED TO REMAIN BELOW 20 KNOTS OVER THE INLAND WATERS.

AFTER A BREAK ON MONDAY ANOTHER FRONT WILL MOVE THROUGH THE AREA
TUESDAY. THIS SYSTEM ALSO LOOKS WEAK WITH THE BEST CHANCES FOR SMALL
CRAFT ADVISORY WINDS IN THE CENTRAL AND EASTERN STRAIT BEHIND THE
FRONT.

FORECAST CONFIDENCE IS LOW BEYOND TUESDAY WITH MODEL SOLUTIONS
VARYING FROM RUN TO RUN. PREVIOUS RUNS HAD A SURFACE RIDGE BUILDING
INTO THE AREA BUT THE 00Z GFS IS INDICATING ANOTHER WEAK FRONT
MOVING THROUGH THE WATERS. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS.

&&

$$

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





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