Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241609
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 AM PDT SUN APR 24 2016

.SYNOPSIS...AN UPPER TROUGH WILL MOVE OVER WESTERN WASHINGTON
THROUGH TONIGHT WITH SHOWERS AND COOL WEATHER. THE REST OF THE
WEEK WILL BE MAINLY DRY WITH WEAK HIGH PRESSURE ALOFT IN CONTROL.

&&

.SHORT TERM...THE UPPER LEVEL TROUGH JUST OFFSHORE DIGS INTO NRN
CALIF THROUGH THIS EVENING. A RESIDUAL TROUGH AXIS SHIFTS OVER
WRN WA THROUGH TONIGHT AND THAT SHOULD KEEP SOME SHOWERS GOING.
THERE IS RAIN IN THE PSCZ THIS MORNING...THE CONVERGENCE ZONE MAY
SAG SOUTH AND DRY UP SOMEWHAT THROUGH THE EVENING. AREAS OUTSIDE
THE PSCZ WILL JUST HAVE A FEWSCATTERED SHOWERS AND SUNBREAKS. BY
MONDAY MORNING THE UPPER TROUGH WILL BE OVER THE GREAT BASIN
AND THE RESIDUAL TROUGH AXIS UP THROUGH WRN WA MAY STILL BE GIVING
SCATTERED SHOWERS. THE TROUGH AXIS FINALLY MOVES INLAND IN THE
AFTERNOON AND NW FLOW ALOFT DRIES UP THE AIR BY EVENING WITH
THE AIR MASS STABILIZING. MONDAY NIGHT SHOULD BE MOSTLY CLEAR
AND MOST OF TUESDAY LOOKS LIKE A NICE DAY TIL MOISTURE AHEAD OF
THE NEXT FRONT ARRIVES FOR INCREASING CLOUDS IN THE AFTERNOON.
THE MODELS HAVE MOSTLY BEEN SHOWING THAT FRONT SPLITS AND ONLY
THE COAST AND OLYMPICS HAVE A CHANCE OF LIGHT RAIN TUE EVENING.

.LONG TERM...NO ORGANIZED WEATHER SYSTEMS ARE EXPECTED WEDNESDAY
THROUGH SATURDAY. THE REMNANTS OF A FRONT MIGHT BRING A FEW
SHOWERS WEDNESDAY. MODELS GENERALLY AGREE WEAK HIGH PRESSURE ALOFT
WILL BE OVER THE REGION ON THURSDAY. A WEAK UPPER SHORT WAVE
COULD BRING A FEW SHOWERS AGAIN FRIDAY.

THE WEATHER SATURDAY IS MORE UNCERTAIN. THE GFS BRINGS A WET
FRONTAL SYSTEM ONSHORE BUT THIS IS A NEW WRINKLE. THE ECMWF IS
DRY WITH AN UPPER RIDGE. THE GEM SHOWS A FRONT REACHING THE COAST
LATE IN THE DAY. NO CHANGES WERE MADE TO THE EXISTING DRY FORECAST
FOR SATURDAY GIVEN ALL THE CURRENT UNCERTAINTY IN THE MODELS.
SCHNEIDER

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL MAINTAIN A COOL AND UNSTABLE
AIR MASS TODAY FOR SHOWERS AND A CHANCE OF THUNDERSTORMS. THE AIR
MASS IS MOIST WITH SOUTHERLY FLOW ALOFT. MVFR CIGS ARE POSSIBLE IN
SHOWERS...ESPECIALLY BETWEEN KPAE AND KSEA WHERE THERE IS A PUGET
SOUND CONVERGENCE ZONE. THE PSCZ WILL SHIFT SOUTH THROUGH KING
COUNTY THIS EVENING THEN DISSIPATE AS ONSHORE FLOW WEAKENS. 33

KSEA...SHOWERS FROM THE CONVERGENCE ZONE TODAY WITH MVFR CIGS. WINDS
BECOMING VARIABLE AND SHIFTING TO NORTHERLY BY 21Z. 33

&&

.MARINE...MODERATE TO STRONG ONSHORE FLOW CONTINUES TODAY WITH HIGH
PRESSURE OVER THE NE PAC. SMALL CRAFT ADVISORIES ARE IN EFFECT FOR
ALL WATERS EXCEPT FOR PUGET SOUND AND HOOD CANAL. THE COASTAL WATERS
WILL ALSO SEE WEST SWELLS BUILDING TO 10 TO 11 FEET. ONSHORE FLOW
WILL CONTINUE THROUGH EARLY THIS WEEK. A WEAK COLD FRONT WILL
DISSIPATE OVER THE COASTAL WATERS EARLY WEDNESDAY. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT PUGET SOUND AND HOOD
     CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

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