Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 282257
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST SAT FEB 28 2015

.SYNOPSIS...AN UPPER RIDGE AND OFFSHORE FLOW WILL BRING ONE MORE
SUNNY DAY TO WESTERN WASHINGTON SUNDAY. A WEAK WEATHER SYSTEM WILL
MOVE THROUGH THE AREA SUNDAY NIGHT FOR A CHANCE OF LIGHT RAIN. DRY
WEATHER WILL PREVAIL FOR THE REMAINDER OF NEXT WEEK UNDER THE
INFLUENCE OF AN UPPER RIDGE AND LOW LEVEL OFFSHORE FLOW.

&&

.SHORT TERM...AN UPPER RIDGE AND LOW LEVEL OFFSHORE FLOW WILL GIVE
DRY WEATHER THROUGH SUNDAY. MODELS SHOW SOME HIGH LEVEL MOISTURE ON
SUNDAY SO THE SUNSHINE MIGHT BE FILTERED BY HIGH CLOUDS AT TIMES.

A WEAK SHORT WAVE IN THE NORTHWEST FLOW ALOFT WILL BRING A CHANCE OF
RAIN SUNDAY NIGHT. THE ECMWF IS A BIT OF AN OUTLIER...SUGGESTING AT
LEAST A LITTLE RAIN ALL AREAS BUT THIS SOLUTION IS BEING DOWNPLAYED
IN THE FORECAST FOR NOW. ALL OTHER MODELS HAVE SPOTTY AND VERY LIGHT
RAIN AT MOST WITH THE BEST CHANCES NEAR THE COAST.

THE SHORT WAVE WILL MOVE SOUTH OF THE FORECAST AREA MONDAY MORNING.
A FEW SHOWERS MAY LINGER OVER THE CASCADES OR FAR SOUTH IN THE
MORNING. OTHERWISE...IT SHOULD BE A DRY DAY WITH DECREASING CLOUDS.

AN UPPER RIDGE OVER THE EASTERN PACIFIC WILL ONCE AGAIN BE IN
CONTROL ON TUESDAY WITH LOW LEVEL OFFSHORE FLOW FOR ANOTHER DRY AND
MOSTLY SUNNY DAY. SCHNEIDER

.LONG TERM...AN UPPER RIDGE WILL BE IN CONTROL WEDNESDAY THROUGH
SATURDAY FOR A STRETCH OF DRY WEATHER. EARLIER MODELS HAD BEEN
SHOWING A WEAK SYSTEM COMING OVER THE TOP OF THE RIDGE...BRINGING A
CHANCE OF RAIN LATER IN THE WEEK...BUT NOW IT LOOKS DRY FOR THE
ENTIRE PERIOD. TEMPERATURES WILL BE NEAR NORMAL...HIGHS IN THE LOWER
TO MID 50S AND LOWS MOSTLY IN THE 30S. SCHNEIDER

&&

.HYDROLOGY...FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

&&

.AVIATION...A LARGE UPPER LEVEL RIDGE CENTERED OVER THE NE PACIFIC
ALONG 140W WILL MAINTAIN DRY NORTHERLY FLOW OVER W WA THROUGH
SUNDAY. A SURFACE RIDGE OVER SE B.C. AND W MT WILL MAINTAIN DRY LOW
LEVEL OFFSHORE FLOW.

THE AIR MASS WILL REMAIN DRY THIS WEEKEND WITH UNRESTRICTED VFR
CONDITIONS...ALTHOUGH THERE COULD STILL BE SOME ISOLATED RIVER
VALLEY FOG DURING THE EARLY MORNING HOURS.

KSEA...UNRESTRICTED VFR THIS WEEKEND. SURFACE WINDS WILL REMAIN N
8-15 KT THROUGH 02Z THEN EASE TO 4-8 KT. KAM

&&

.MARINE...WEAK OFFSHORE FLOW WILL CONTINUE TONIGHT AND
SUNDAY...BETWEEN A SURFACE RIDGE EXTENDING FROM SE B.C. TO W
MT...AND A WEAK SURFACE TROUGH NEAR THE WA COAST.

SURFACE WINDS HAVE BEEN GRADUALLY DIMINISHING THIS AFTERNOON...BUT A
BRIEF SURGE OF NORTHERLY 15-25 KT WINDS WILL AFFECT THE COASTAL
WATERS THIS EVENING. OTHERWISE WINDS WILL REMAIN BELOW SCA LEVELS
THROUGH SUNDAY.

AN UPPER LEVEL TROUGH IS STILL EXPECTED TO MOVE SE ACROSS THE AREA
SUNDAY NIGHT. MESOSCALE MODELS STILL SHOW A BRIEF PERIOD OF SCA
LEVEL N WINDS DEVELOPING AS THE TROUGH CROSSES THE AREA.

AFTER THE UPPER LEVEL TROUGH MOVES S...ANOTHER SURFACE HIGH WILL
BUILD OVER B.C. ON MONDAY...THEN WEAKEN TUESDAY NIGHT THROUGH
WEDNESDAY. MODERATE TO POSSIBLY STRONG NE OFFSHORE FLOW WILL DEVELOP
FROM THE N INLAND WATERS...EXTENDING THROUGH THE STRAIT OF JUAN DE
FUCA AND OUT OVER THE NORTHERN COASTAL WATERS. SCA WINDS ARE
EXPECTED MONDAY NIGHT AND TUESDAY AND THERE IS SOME POTENTIAL FOR
GALE FORCE WINDS. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL ZONES 153...156...173...176.

&&

$$

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








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