Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 041006
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 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...AN UPPER LEVEL LOW IS SPINNING OVERHEAD THIS MORNING
AND WILL SHIFT SOUTH INTO WESTERN OREGON THIS AFTERNOON. SO FAR
SHOWERS ARE MAINLY OVER SOUTHERN B.C. AND OREGON WITH NOT MUCH
ACTION ACROSS WESTERN WA. MODELS DO SHOW SOME SHOWERS POPPING UP
OVER THE MOUNTAINS THIS AFTERNOON AND ACROSS THE SOUTHERN PORTION ON
THE CWA...SOUTH OF KOLM. SHOWER COVERAGE WILL BE ISOLATED IF
ANYTHING DOES DEVELOP. OTHERWISE IT WILL BE ANOTHER COOL DAY TODAY
WITH TEMPS AGAIN IN THE 60S.

THE UPPER LEVEL LOW WILL EXIT EAST ON SATURDAY WHILE AN UPPER LEVEL
RIDGE MOVES IN FROM THE WEST. THIS RIDGE WILL BRING DRIER AND
SLIGHTLY WARMER WEATHER TO WESTERN WA.

A WEAK COLD FRONT WILL BRING SOME CLOUDS AND RAIN ON SUNDAY AS IT
MOVES INLAND. THE COAST SHOULD SEE SOME PRECIP EARLY SUNDAY MORNING.
THE FRONT DOES WEAKEN AS IT MOVES INLAND BUT WE COULD STILL SEE A
FEW SHOWERS THROUGH THE INTERIOR. LOW LEVEL ONSHORE FLOW WILL
INCREASE BEHIND THE FRONT LATE SAT AFTERNOON AND EVENING. THE
ONSHORE FLOW AND TRAILING UPPER LEVEL TROUGH WILL MAINTAIN A CHANCE
OF SHOWERS THROUGH SUNDAY EVENING.

NORTHERLY FLOW WILL PREVAIL ON LABOR DAY AS ANOTHER RIDGE BUILDS
OVER THE OFFSHORE WATERS. THE FORECAST REMAINS DRY WITH TEMPS IN THE
MID TO UPPER 60S. 33

.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 THE WA COAST IS MOVING SLOWLY
SOUTH INTO OREGON THIS MORNING.  THE MOIST AIR MASS HAS BECOME
MOSTLY STABLE THIS MORNING AND THE COMBINATION HAS GIVEN A MIXED BAG
OF CONDITIONS OVER WESTERN WA. SCT-BKN CIGS 3-6K OVER MOST
AREAS...BUT THERE ARE AREAS OF MVFR AND IFR CIGS AND VSBYS AROUND.
MOST OF THESE LOWER CONDITIONS SHOULD IMPROVE AND/OR BURN OFF BY
EARLY AFTERNOON.

KSEA...MVFR OR IFR CEILINGS ARE LIKELY THIS MORNING. ANY LOWER CIGS
THAT DO DEVELOP SHOULD NOT LAST PAST NOON. LIGHT NORTHERLY WINDS
SHOULD INCREASE A BIT IN THE AFTERNOON.

&&

.MARINE...ONSHORE GRADIENTS WILL RETURN TODAY AND STRENGTHEN
TONIGHT. SMALL CRAFT ADVISORY WINDS ARE POSSIBLE OVER THE COASTAL
WATERS AND THROUGH THE STRAIT OF JUAN DE FUCA THIS EVENING. HIGH
PRESSURE WILL BUILD OVER THE WATERS INTO THE WEEKEND.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

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