Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 041641
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PDT FRI SEP 4 2015

.SYNOPSIS...AN UPPER LEVEL LOW WILL MOVE SLOWLY SOUTH THROUGH
WESTERN WASHINGTON TODAY AND INTO WESTERN OREGON. AN UPPER LEVEL
RIDGE WILL BRING DRY AND SLIGHTLY WARMER WEATHER ON SATURDAY. A WEAK
COLD FRONT WILL BRING SOME RAIN ON SUNDAY. DRY WEATHER WILL RETURN
ON LABOR DAY.

&&

.SHORT TERM...AREAS OF MORNING LOW CLOUDS UP AND DOWN THE I-5
CORRIDOR WILL GIVE WAY TO SOME AFTERNOON SUNSHINE. THERE WILL BE
ISOLATED SHOWERS...MAINLY OVER THE MOUNTAINS. AN UPPER LEVEL LOW
IS OVER THE REGION. THE UPPER LOW WILL BE REPLACED BY A WEAK
UPPER RIDGE ON SATURDAY FOR A DAY OF SOMEWHAT WARMER AND SUNNIER
WEATHER. A FRONT WILL BRING CLOUDS AND SOME RAIN ON SUNDAY.
INCREASING LOW LEVEL ONSHORE FLOW BEHIND THE FRONT LATER SAT
WILL KEEP A CHANCE OF SHOWERS IN THE FORECAST SUNDAY EVENING.
NORTHERLY FLOW WILL DEVELOP FOR LABOR DAY AS AN UPPER RIDGE BUILDS
OFFSHORE.

.LONG TERM...A WARM FRONT WILL MOVE INTO SOUTHERN B.C. NEXT TUESDAY
WHICH MAY CLIP THE NORTHERN TIER OF THE CWA FOR A CHANCE OF RAIN.
POPS ARE LOW AT 20-30 PERCENT FOR NOW. OTHERWISE IT LOOKS LIKE AN
UPPER LEVEL RIDGE WILL REMAIN IN CONTROL ACROSS THE PAC NW FOR
ANOTHER PERIOD OF DRY WEATHER. TEMPERATURES THROUGH THE EXTENDED
PERIOD WERE NUDGED UPWARDS A FEW DEGREES FROM THE PREVIOUS FORECAST.
THE RIDGE MAY START TO WEAKEN AND FLATTEN BY FRIDAY AS AN UPPER
LEVEL LOW DEVELOPS OVER CENTRAL B.C. 33

&&

.AVIATION...AN UPPER LEVEL LOW OVER SOUTHWEST WASHINGTON IS MOVING
SLOWLY SOUTH INTO OREGON THIS MORNING. THE FLOW ALOFT IS LIGHT AND
VARIABLE...AND WILL SWITCH TO NORTHERLY AND STRENGTHEN EARLY
SATURDAY. THE MOIST AND MOSTLY STABLE AIRMASS FROM EARLY THIS
MORNING WHICH IS GIVING THE MVFR AND IFR CIGS AT THE TERMINALS
SHOULD DESTABILIZE A BIT LATER THIS MORNING AND INTO THE
AFTERNOON...GIVING VFR CONDITIONS. VFR CONDITIONS SHOULD CONTINUE
THROUGH THE PERIOD FOR THE MOST PART...WITH THE EXCEPTION OF SOME
PATCHY FOG IN THE EARLY MORNING HOURS...WITH THE GREATEST CHANCE AT
KOLM AND KHQM.

KSEA...MVFR AND IFR CIGS THIS MORNING SHOULD BURN OFF BY EARLY IN
THE AFTERNOON. LIGHT NORTHERLY WINDS SHOULD INCREASE A BIT IN THE
AFTERNOON AND THEN SWITCH TO LIGHT SLY AROUND OR SOON AFTER
MIDNIGHT. JSMITH

&&

.MARINE...WESTERLY ONSHORE GRADIENTS WILL RETURN TODAY AND
STRENGTHEN TONIGHT. SMALL CRAFT ADVISORY LEVEL NORTHERLY WINDS ARE
EXPECTED OVER THE COASTAL WATERS LATE THIS AFTERNOON THROUGH THIS
EVENING. GRADIENTS WILL SWITCH TO MORE SWLY AND THEN SLY LATE
SATURDAY INTO SUNDAY AS A SURFACE LOW PRESSURE SYSTEM AND ITS
ASSOCIATED FRONT DIP ALONG THE BC COAST AND INTO THE AREA. SMALL
CRAFT ADVISORY LEVEL WINDS WILL OCCUR IN THE STRAIT AHEAD OF THE
FRONT LATE SATURDAY. WEAK TO MODERATE ONSHORE FLOW WILL RESUME AND
CONTINUE THROUGH THE BEGINNING OF NEXT WEEK. JSMITH

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS AND
     CENTRAL AND EAST STRAIT OF JUAN DE FUCA

&&

$$

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