Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 112226
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
326 PM PDT FRI APR 11 2014

.SYNOPSIS...THE UPPER LEVEL TROUGH BRUSHING BY THE REGION TONIGHT
WILL KEEP CLOUDS AND A CHANCE OF SHOWERS MAINLY FOR THE COAST AND
NORTH CASCADES INTO EARLY SATURDAY MORNING. A STRONG UPPER LEVEL
RIDGE WILL BUILD OFFSHORE THIS WEEKEND BRINGING WARMER TEMPERATURES
AND SUNSHINE THROUGH MONDAY. THE RIDGE WILL SHIFT INLAND AND WEAKEN
MONDAY AFTERNOON ALLOWING A SERIES OF SYSTEMS TO PASS THROUGH THE
PACIFIC NORTHWEST BRINGING COOLER AND UNSETTLED THROUGH THE
REMAINDER OF THE NEXT WEEK.

&&

.SHORT TERM...THE WEAK UPPER LEVEL TROUGH THAT HAS BEEN SHIFTING
SOUTH AND EAST THROUGH BRITISH COLUMBIA TODAY HAS SPREAD MID AND
HIGH LEVEL CLOUDS INTO WESTERN WASHINGTON. HAVE KEPT A CHANCE OF
LIGHT SHOWERS FOR THE COAST AND NORTH CASCADES TONIGHT AS THE UPPER
LEVEL TROUGH CONTINUES TO PUSH SOUTH AND EAST OF THE AREA. THE UPPER
LEVEL RIDGE BUILDING WEST OF 130W WILL CONTINUE TO AMPLIFY AND
SLOWLY SHIFT EAST THROUGH THE WEEKEND. EXPECT MORNING CLOUDS
SATURDAY CLEARING TO MOSTLY SUNNY SKIES BY THE AFTERNOON ON
SATURDAY... NORTHWEST FLOW ALOFT AND NORTHERLY SURFACE GRADIENTS
WILL HELP KEEP HIGH TEMPERATURES SATURDAY SIMILAR TO TODAY DESPITE
THE ADDITIONAL SUNSHINE.

THE UPPER RIDGE AXIS WILL SHIFT INSIDE OF 130W SUNDAY MORNING WHILE
A THERMALLY INDUCED TROUGH AT THE SURFACE BEGINS TO SHIFT NORTHWARD
ALONG THE OREGON AND SOUTHWEST WASHINGTON COAST. THIS WILL DRIVE
LIGHT OFFSHORE FLOW AT LOW LEVELS AND BUMP HIGH SUNDAYS TEMPERATURES
INTO MID AND UPPER 60S.

.LONG TERM...THE RIDGE AXIS WILL SHIFT ONSHORE MONDAY MORNING AND
EAST OF THE CASCADES LATE IN THE AFTERNOON HELPING WARMER
TEMPERATURES LINGER MONDAY...ESPECIALLY OVER THE INTERIOR. AREAS
FROM SEATTLE SOUTHWARD COULD REACH INTO THE LOWER 70S WHILE HIGH
TEMPERATURES FOR THE COAST WILL LIKELY PEAK EARLIER IN THE DAY BUT
REMAIN IN THE UPPER 50S AS ONSHORE FLOW BECOMES ESTABLISHED THERE.
MODELS AGREE ON PUSHING THE RIDGE EAST OF OUR AREA MONDAY EVENING
AND A RETURN TO MORE UNSETTLED WEATHER FOR THE REMAINDER OF THE
WEEK. MODELS A LITTLE MORE CONSISTENT IN ADVERTISING A WEAK SYSTEM
TUESDAY MORNING AND A WETTER...MORE CONSOLIDATED SYSTEM ON THURSDAY.
THERE REMAINS SIGNIFICANT DIFFERENCES IN HOW THE MODELS HANDLE THE
TRANSITION BETWEEN THE WEAKER SYSTEM ON TUESDAY AND THURSDAYS WETTER
SYSTEM. THE EUROPEAN REMAINS THE WETTER MODEL WHILE THE GFS AND
CANADIAN MODELS SHOW A BIT OF A BREAK WEDNESDAY OR WEDNESDAY NIGHT.
WHILE CONFIDENCE IN THE DETAILS FOR THE EXTENDED IS NOT HIGH...THERE
IS GENERALLY A HIGHER DEGREE OF CONFIDENCE IN THE IDEA OF A
TRANSITION TO A MORE UNSETTLED AND SEASONAL PATTERN NEXT WEEK.

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED ON AREA RIVERS...EXCEPT
THE STILLAGUAMISH...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 CONTINUED 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 EARLY
NEXT WEEK.

EXCEPT FOR A CHANCE OF LIGHT SHOWERS TODAY...THE WEATHER WILL BE DRY
THROUGH THIS WEEKEND AND INTO MONDAY. A SHIFT TO A WESTERLY FLOW
PATTERN EARLY NEXT WEEK WILL BRING A CHANCE OF RAIN BACK TO THE AREA
LATE MONDAY NIGHT AND TUESDAY...BUT CURRENT MEDIUM RANGE MODELS DO
NOT INDICATE  THE THREAT OF SIGNIFICANT PRECIPITATION THROUGH THE
MIDDLE OF NEXT WEEK.

&&

.AVIATION...CLOUDS NEVER REALLY FILLED IN SOUTH OF SEATTLE AND THE
CLOUDIEST AREAS THIS AFTERNOON ARE THE COAST AND WEST SLOPES OF THE
CASCADES NORTH OF ABOUT I-90. BUT WITH ONSHORE/WLY FLOW THIS EVENING
SOME AREAS OF CLOUDS MAY INCREASE LATER TONIGHT...BUT THEN SCATTER
OUT PRETTY QUICKLY SATURDAY MORNING. DRY NORTHERLY FLOW WILL GIVE
MOSTLY SUNNY SKIES SATURDAY AFTERNOON.


KSEA...MAINLY SCATTERED CLOUDS SO FAR TODAY BUT A LAYER MAY SET UP
OVERNIGHT...AND THEN SCATTER OUT AGAIN AROUND MID MORNING SATURDAY.
THE LIGHT AND VARIABLE WIND TODAY WILL BECOME NW THIS AFTERNOON AND
EVENING AND REMAIN NLY SAT.

&&

.MARINE...ONSHORE FLOW THIS EVENING...THERE IS A SMALL CRAFT
ADVISORY FOR WESTERLIES IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE
FUCA...AS WELL AS FOR ADMIRALTY INLET BUT THAT IS TAKING LONGER TO
DEVELOP THIS AFTERNOON. MORE NORTHERLY FLOW WILL DEVELOP ON SATURDAY
AND THEN TURN EASTERLY BY SUNDAY AS A THERMALLY INDUCED SURFACE
TROUGH FORMS ALONG THE COAST. THE FLOW WILL THEN FLIP BACK TO
ONSHORE MONDAY AND MONDAY NIGHT AS THE SURFACE TROUGH SHIFTS INLAND
AND EAST OF THE CASCADES.

&&

.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...SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT OF JUAN DE FUCA
AND ADMIRALTY INLET.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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