Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 122151
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT SAT APR 12 2014

.SYNOPSIS...A STRONG UPPER LEVEL RIDGE AND OFFSHORE FLOW WILL KEEP
WESTERN WASHINGTON DRY SUNDAY AND MONDAY. A SERIES OF WEAK WEATHER
SYSTEMS WILL REACH THE AREA BEGINNING MONDAY NIGHT. CONDITIONS WILL
BE COOLER WITH WET WEATHER LIKELY TUESDAY AND THURSDAY...AND A
CHANCE OF SHOWERS ON OTHER DAYS.

&&

.SHORT TERM...GOOD CLEARING THIS AFTERNOON HAS LEFT THE AREA UNDER
MOSTLY SUNNY SKIES. TONIGHT WILL BE MOSTLY CLEAR WITH PATCHY FOG IN
THE SOUTHWEST INTERIOR. SUNDAY LOOKS WARMER AS THE UPPER RIDGE
BUILDING OFFSHORE SHARPENS AND MOVES EAST. AT THE SAME TIME
NORTHERLY SURFACE FLOW GAINS A MORE OFFSHORE COMPONENT. THIS WILL
GIVE SUNNY SKIES WITH HIGHS 65 TO 70.

ON MONDAY AN UPPER LEVEL LOW MOVES BY TO THE NORTH. FLOW AT THE
SURFACE TURNS STRONGLY ONSHORE AND HEIGHTS FALL SIGNIFICANTLY.
CLOUDS WILL DEVELOP ON THE COAST THOUGH INLAND AREAS SHOULD REMAIN
MOSTLY SUNNY. HIGHS WILL BE 5-10 DEGREES LOWER THAN SUNDAY. GALE
FORCE WEST WINDS ARE POSSIBLE IN THE STRAIT WITH BREEZY CONDITIONS
OVER ADJACENT LAND AREAS...ESPECIALLY MONDAY NIGHT.

HEIGHTS WILL BE LOWER ON TUESDAY AS THE PATTERN REMAINS TROUGHY.
MODELS ALL HAVE AT LEAST A LITTLE RAIN. HAVE INCREASED POPS TO
LIKELY FOR THE COAST AND MOUNTAINS IN THE MORNING...AND FOR
EVERYWHERE IN THE AFTERNOON. HIGHS WILL BE IN THE 50S. BURKE

.LONG TERM...THERE IS BRIEF RIDGING AT THE SURFACE AND ALOFT ON
WEDNESDAY. MODELS STILL HAVE A FEW DRIBS AND DRABS OF RAIN BUT
WEDNESDAY COULD TURN OUT MOSTLY DRY. HAVE POPS IN THE LOW CHANCE
CATEGORY FOR WEDNESDAY. ANOTHER SYSTEM ARRIVES THURSDAY IN BOTH THE
GFS AND THE EURO AND HAVE INCREASED POPS TO LIKELY FOR THAT SYSTEM
AS WELL. MODELS DIVERGE AFTER THAT WITH THE GFS NOTABLY DRY AND THE
EURO WET...HAVE BROAD BRUSH CHANCE POPS FRIDAY AND SATURDAY. BURKE

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY ON AREA RIVERS...EXCEPT THE
NORTH FORK OF THE STILLAGUAMISH EAST OF OSO...FOR THE NEXT 7 DAYS.

A FLOOD WARNING REMAINS IN EFFECT UNTIL FURTHER NOTICE FOR THE
NORTH FORK OF THE STILLAGUAMISH RIVER IN SNOHOMISH COUNTY JUST
UPSTREAM OF THE SR 530 LANDSLIDE. FLOODING CONTINUES AS A RESULT
OF WATER POOLED BEHIND THE DEBRIS DAM THAT PARTIALLY BLOCKS THE
RIVER.

THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON AND THE POOL
UPSTREAM OF THE SR 530 SLIDE WILL CONTINUE FALLING THROUGH MONDAY AS
A STRONG UPPER LEVEL RIDGE BRINGS DRY WEATHER TO THE AREA. A SHIFT
TO A WESTERLY FLOW PATTERN MONDAY NIGHT AND TUESDAY WILL BRING A
CHANCE OF RAIN BACK INTO THE AREA. RAINFALL WITH SYSTEMS MONDAY
NIGHT THROUGH THE END OF NEXT WEEK ARE NOT EXPECTED TO BE
HYDROLOGICALLY SIGNIFICANT. ALBRECHT

&&

.AVIATION...MAINLY SCATTERED CLOUDS ACROSS WESTERN WA THIS AFTERNOON
WILL GIVE WAY TO CLEAR SKIES TONIGHT AND SUNDAY WITH DRY AIR AND
NORTHERLY FLOW ALOFT. AN UPPER LEVEL RIDGE IS JUST OFFSHORE AND THAT
WILL MOVE OVER THE REGION LATER SUNDAY AND WEAKEN AS AN UPPER TROUGH
AND COLD FRONT NEAR THE AREA.

KSEA...CLEAR TONIGHT AND SUNDAY. A NORTHERLY BREEZE THIS EVENING
WILL BECOME LIGHT NORTHEAST OVERNIGHT.

&&

.MARINE...NORTHERLY FLOW WILL PEAK THIS EVENING AND THEN GRADIENTS
WILL WEAKEN AND TURN MORE EASTERLY SUNDAY. THERMALLY INDUCED LOW
PRESSURE WILL SET UP ALONG THE OREGON COAST SUNDAY. ONSHORE FLOW
WILL DEVELOP MONDAY AFTERNOON AND EVENING AS A WEATHER SYSTEM NEARS
THE AREA...THE STRONGEST WESTERLY FLOW WILL BE IN THE STRAIT MONDAY
NIGHT WITH 20-30KT IN THE FORECAST FOR NOW.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING REMAINS IN EFFECT FOR THE NORTH FORK OF THE
     STILLAGUAMISH RIVER EAST OF THE SR 530 LANDSLIDE.

PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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





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