Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 111544
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
843 AM PDT FRI APR 11 2014

.SYNOPSIS...AN UPPER LEVEL TROUGH MOVING INTO THE REGION TODAY WILL
SPREAD CLOUDS ACROSS WESTERN WASHINGTON AND A CHANCE OF SHOWERS FOR
THE COAST AND NORTH CASCADES. A STRONG UPPER LEVEL RIDGE WILL BUILD
OFFSHORE THIS WEEKEND FOR WARMER TEMPERATURES AND MORE SUNSHINE. THE
RIDGE WILL SHIFT INLAND AND WEAKEN EARLY NEXT WEEK WITH A RETURN TO
A MORE  UNSETTLED WEATHER PATTERN.

&&

.SHORT TERM...THE WEAK WEATHER SYSTEM PUSHING INTO BRITISH COLUMBIA
THIS MORNING CONTINUES TO SPREAD HIGH AND MID LEVEL CLOUDS FROM THE
NORTHWEST ACROSS WESTERN WASHINGTON. PRECIPITATION ASSOCIATED WITH
THIS SYSTEM WILL GENERALLY REMAIN NORTH OF THE BORDER WITH A CHANCE
OF SHOWERS OVER THE NORTH COAST AND NORTH CASCADES...LITTLE MORE
THAN A FEW HUNDREDTHS AT BEST. UPPER LEVEL RIDGING WILL BUILD
OFFSHORE TONIGHT AND SLOWLY SHIFT EAST THROUGH THE WEEKEND. EXPECT
MORNING CLOUDS SATURDAY FOLLOWED BY MOSTLY SUNNY CONDITIONS BY
AFTERNOON ON SATURDAY. FLOW ALOFT WILL REMAIN NORTHWEST SATURDAY AS
THE RIDGE BUILDS OFFSHORE WITH DECENT NORTHERLY SURFACE GRADIENTS IN
THE AFTERNOON WHICH WILL HELP KEEP HIGH TEMPERATURES SATURDAY
SIMILAR TO TODAY DESPITE THE ADDITIONAL SUNSHINE.

THE UPPER RIDGE AXIS MOVES CLOSER TO THE COAST ON SUNDAY AND
THERMALLY INDUCED LOW PRESSURE AT THE SURFACE BEGINS TO SHIFT
NORTHWARD ALONG THE OREGON COAST WITH LIGHT LOW LEVEL OFFSHORE FLOW
DEVELOPING. HIGH TEMPERATURES ON SUNDAY WILL RISE INTO MID AND UPPER
60S FOR MUCH OF THE REGION. MODELS TRENDING SLOWER ON THE EASTWARD
PROGRESSION OF THE UPPER LEVEL RIDGE...KEEPING THE RIDGE AXIS OVER
WESTERN WASHINGTON THROUGH MONDAY AFTERNOON. THIS SUGGESTS A DELAY
IN THE TRANSITION TO COOLER MORE UNSETTLED WEATHER EARLY NEXT
WEEK...MOST NOTABLY POTENTIALLY WARMER TEMPERATURES FOR THE INTERIOR
ON MONDAY.

.LONG TERM...THE UPPER LEVEL RIDGE AXIS MOVES OVER WESTERN
WASHINGTON ON MONDAY AND EAST OF THE CASCADES MONDAY NIGHT.
ACCORDINGLY THIS COULD BE THE WARMEST DAY OF THE NEXT 7...WITH AREAS
FROM SEATTLE SOUTHWARD POTENTIALLY REACHING INTO THE LOWER 70S.
TEMPERATURE FORECASTS FOR THE COAST ON MONDAY COULD BE A LITTLE MORE
CHALLENGING WHERE TEMPERATURES MAY PEAK EARLIER IN THE DAY BEFORE
ONSHORE FLOW BECOMES ESTABLISHED. MODELS AGREE ON PUSHING THE RIDGE
EAST OF OUR AREA LATE MONDAY AND A RETURN TO MORE UNSETTLED WEATHER.
HOWEVER THERE ARE SIGNIFICANT DIFFERENCES IN HOW THE MODELS HANDLE
THE PATTERN FOR TUESDAY ONWARD. THE EVENING GFS DEVELOPS A CUTOFF
LOW TO OUR SOUTH ON TUESDAY WHILE THE EURO BRINGS A TROUGH ONSHORE
WELL TO OUR NORTH. THE CANADIAN BRINGS A SHARP TROUGH RIGHT INTO
WESTERN WASHINGTON. WHILE CONFIDENCE IN THE DETAILS FOR THE EXTENDED
REMAINS LOW...THERE IS A HIGHER DEGREE OF CONFIDENCE THAT THE
PATTERN WILL TRANSITION TO A MORE UNSETTLED PERIOD THROUGH MUCH OF
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 PROBABLY INTO MONDAY. A SHIFT TO A WESTERLY
FLOW PATTERN EARLY NEXT WEEK WILL BRING A CHANCE OF RAIN BACK TO THE
AREA...BUT CURRENT MEDIUM RANGE MODELS DO NOT INDICATE  THE THREAT
OF SIGNIFICANT PRECIPITATION THROUGH THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...AT 8AM IT WAS CLOUDY ACROSS MUCH OF WRN WA...BUT STILL
MOSTLY SUNNY SOUTH OF SEATTLE. BUT THAT AREA SHOULD FILL IN WITH
CLOUDS AS THEY DAY WEARS ON. AT 8AM THE CASCADES NORTH OF ABOUT I-90
HAD CLOUDS BUT IT WAS CLEAR SOUTH OF THERE...BUT THE SOUTH CASCADES
SHOULD SEE INCREASING CLOUDS AS WELL. A WEAK FRONT WILL DISSIPATE AS
IT MOVES INTO NW WA THIS MORNING. THERE HAS BEEN SOME LIGHT RAIN AT
UIL. ONSHORE FLOW WILL INCREASE INTO THIS EVENING. THE FLOW ALOFT IS
WNW.

KSEA...CLOUDS WILL INCREASE TODAY AS MOISTURE CONTINUES TO PUSH IN
WITH A RATHER WEAK SYSTEM...BUT MAINLY INCREASING LOW LEVEL ONSHORE
FLOW WILL BRING IN THE CLOUDS. THE METRO AREA WILL BE IN AN AREA OF
LIGHT CONVERGING WINDS TODAY AND THEN A NLY BREEZE WILL DEVELOP THIS
EVENING.

&&

.MARINE...ONSHORE FLOW WILL INCREASE AS A WEAK FRONT MOVES ASHORE
AND DISSIPATES TODAY. THERE IS A SMALL CRAFT ADVISORY FOR WESTERLIES
IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA. 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.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
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