Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 100956
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
255 AM PDT THU APR 10 2014

.SYNOPSIS...WEAK HIGH PRESSURE ALOFT WILL PREVAIL OVER THE REGION
TODAY. A WEAK WEATHER SYSTEM PASSING TO OUR NORTH WILL CLIP THE AREA
ON FRIDAY. HIGH PRESSURE ALOFT WILL BUILD STRONGLY OVER THE REGION
THIS WEEKEND FOR DRY WEATHER WITH ABOVE NORMAL DAYTIME TEMPERATURES.
UNSETTLED CONDITIONS ARE EXPECTED TO RETURN EARLY NEXT WEEK.

&&

.SHORT TERM...WEAK HIGH PRESSURE ALOFT WILL BRING ANOTHER DRY DAY TO
WESTERN WASHINGTON TODAY WITH HIGH TEMPERATURES NEAR OR A LITTLE
ABOVE NORMAL. THE UPPER LEVEL RIDGE IS RATHER DIRTY AND AREAS OF
HIGH AND MID LEVEL MOISTURE MAY LIMIT THE SUNSHINE...ESPECIALLY
ACROSS THE NORTHERN HALF OF THE FORECAST AREA. CLOUDS WILL INCREASE
TONIGHT AS A TROUGH APPROACHES BRITISH COLUMBIA. THIS SYSTEM WILL
ONLY CLIP OUR AREA AND ANY PRECIP THAT DOES FALL WITH IT SHOULD BE
LIMITED TO COASTAL AREAS AND UP IN WHATCOM/SKAGIT COUNTIES. HEIGHTS
ONLY FALL MODESTLY WITH THIS SYSTEM AND TEMPERATURES WILL REMAIN
SEASONABLE DESPITE THE CLOUD COVER.

HIGH AMPLITUDE UPPER LEVEL RIDGING BEGINS TO BUILD OVER THE OFFSHORE
WATERS ON SATURDAY. THE REGION WILL STILL BE UNDER THE INFLUENCE OF
THE TROUGH DURING THE FIRST HALF OF THE DAY...BUT SKIES ARE EXPECTED
TO CLEAR BY AFTERNOON AS SUBSIDENCE TAKES OVER. COOL NORTHERLY
BREEZES WILL PROBABLY KEEP TEMPERATURES IN CHECK SATURDAY AFTERNOON.
THE UPPER RIDGE AXIS PROGRESSES CLOSER TO THE COAST SATURDAY NIGHT
AND LOW LEVEL GRADIENTS TURN OFFSHORE. THIS WILL SET THE STAGE FOR A
WARMING TREND TO BEGIN THE EXTENDED PERIOD.

.LONG TERM...THE UPPER RIDGE AXIS SHOULD BE OVER WESTERN WASHINGTON
ON SUNDAY. THIS ALONG WITH LIGHT OFFSHORE FLOW SHOULD GIVE
TEMPERATURES AN ADDED BOOST WITH SOME SPOTS REACHING HIGHS 10 TO 12
DEGREES ABOVE NORMAL. THE UPPER LEVEL RIDGE AXIS WILL SHIFT EAST OF
THE AREA SUNDAY NIGHT AS A TROUGH APPROACHES 130W. HEIGHTS BEGIN TO
FALL AND SURFACE GRADIENTS TURN ONSHORE. THIS SHOULD COOL
TEMPERATURES A FEW DEGREES AND ADD A FEW CLOUDS TO THE
FORECAST...BUT MONDAY SHOULD BE DRY. THOUGH THEY DISAGREE ON THE
DETAILS...THE EURO AND GFS BOTH SUGGEST A TURN TOWARD A LITTLE MORE
UNSETTLED CONDITIONS IN THE TUESDAY/WEDNESDAY TIMEFRAME. THE GFS IS
MORE EMPHATIC WITH THE STRENGTH OF THE TROUGH THAN THE EURO...BUT
BOTH SUGGEST AT LEAST A LITTLE PRECIP FALLING. NO CHANGES WERE MADE
TO THE EXTENDED FORECAST OVERNIGHT. 27

&&

.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 THIS
WEEKEND.

&&

AVIATION...ONSHORE FLOW WILL CONTINUE ACROSS WESTERN WA TODAY. THE
FLOW ALOFT IS NORTHWESTERLY WITH WEAK HIGH PRES OVER THE REGION. THE
AIR MASS IS STABLE WITH VFR CONDITIONS EXPECTED. 33

KSEA...BKN LAYER NEAR 6000 FT EARLY THIS MORNING WHICH WILL SCATTER
BY THE AFTERNOON. VFR CONDITIONS EXPECTED. SURFACE WINDS WILL REMAIN
LIGHT N/NE. 33

&&

.MARINE...HIGH PRES OVER THE NE PACIFIC WILL MAINTAIN ONSHORE FLOW
ACROSS WESTERN WA TODAY. A WEAK COLD FRONT WILL CROSS THE AREA
FRIDAY MORNING. HIGHEST WIND/WAVES WILL OCCUR AT THE CENTRAL AND
EAST STRAIT OF JUAN DE FUCA. THE FLOW WILL FLIP TO OFFSHORE THIS
WEEKEND AS A SURFACE TROUGH FORMS ALONG THE COAST. 33

&&

.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
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






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