Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 011605
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
905 AM PDT FRI MAY 1 2015

.SYNOPSIS...DRY WEATHER IS EXPECTED TODAY WITH TEMPERATURES A FEW
DEGREES WARMER THAN NORMAL. AN WEAK UPPER LEVEL RIDGE WILL MOVE OVER
THE REGION THIS WEEKEND BRINGING MOSTLY SUNNY SKIES AND WARMER
TEMPERATURES. A FRONT WILL APPROACH THE REGION MONDAY WITH
INCREASING CLOUDS. LOW PRESSURE WILL BRING SHOWERS AND COOLER
TEMPERATURES BACK INTO WESTERN WASHINGTON MONDAY NIGHT THROUGH
WEDNESDAY.

&&

.SHORT TERM...THE FLOW ALOFT ACROSS THE PAC NW IS NEARLY ZONAL WITH
WEAK TROUGHING OVER NORTHERN BRITISH COLUMBIA. A WEAK UPPER LEVEL
FRONT CROSSED WESTERN WA OVERNIGHT. THIS IS WHAT BROUGHT THE
MID/HIGH LEVEL CLOUDS TO THE AREA. THERE IS SOME STRATUS ALONG THE
COAST OTHERWISE SKIES ARE PARTLY TO MOSTLY SUNNY THIS MORNING WITH
THE FRONT NOW OVER MT/ID. POPS WERE REMOVED FROM THE NORTHWEST
INTERIOR TODAY OTHERWISE THE REST OF THE FORECAST IS ON TRACK. WE
WILL SEE HIGHS IN THE MID 50S TO MID 60S TODAY.

THE FORECAST THIS WEEKEND WILL REMAIN DRY AND MILD ACROSS WESTERN WA
AS A WEAK UPPER LEVEL RIDGE MOVES IN. LOW LEVEL ONSHORE FLOW WILL
CONTINUE. TEMPS WILL BE A FEW DEGREES WARMER THAN NORMAL WITH HIGHS
IN THE LOW 70S POSSIBLE ON SUNDAY. 33

.LONG TERM...PREVIOUS DISCUSSION...MONDAY WILL BE A TRANSITION DAY
AS SW FLOW ALOFT DEVELOPS AHEAD OF AN APPROACHING UPPER TROUGH. THE
STRONGER ONSHORE PUSH WILL PROBABLY WAIT UNTIL MONDAY NIGHT WITH
MARINE CLOUDS SURGING INLAND. EXTENDED MODELS ARE IN GOOD AGREEMENT
ON BRINGING THE UPPER LOW ACROSS THE AREA TUESDAY AND WEDNESDAY.
THIS WOULD BE AN UNSTABLE SHOWERY PATTERN WITH COOLER TEMPERATURES.
THE GFS40 INDICATES LI`S AROUND -1 TO -2C DURING TUESDAY/WEDNESDAY
PERIOD SO THERE IS A THREAT OF THUNDERSTORMS JUST ABOUT ANYWHERE.
THIS WILL PROBABLY NEED TO BE INTRODUCED TO THE FORECAST SOON.
MERCER

&&

.AVIATION...AN UPPER TROF OVER BRITISH COLUMBIA WILL MAINTAIN STRONG
WLY FLOW ALOFT ACROSS THE AREA TODAY. EXPECT THE LOW LEVEL ONSHORE
FLOW TO STRENGTHEN THIS AFTERNOON.

MEANWHILE...THERE WERE LOCALIZED CIGS NEAR 1K FT THIS MORNING.
VFR CONDITIONS ARE ANTICIPATED THIS AFTERNOON BUT THERE WILL
LIKELY BE AREAS OF CIGS NEAR 3K FT OVER THE COAST.

KSEA...THERE MIGHT BE A BRIEF CIG NEAR 015 THIS MORNING...
OTHERWISE VFR CONDITIONS WILL PREVAIL. WINDS WILL BECOME NW AT
6-12 KT THIS AFTERNOON.

&&

.MARINE...
HIGH PRES OFFSHORE WITH LOWER PRES E OF THE CASCADES WILL RESULT
IN ONSHORE FLOW OF VARYING STRENGTH THROUGH THIS WEEKEND. THE
ONSHORE PRESSURE GRADIENT WILL STRENGTHEN THIS AFTERNOON...LEADING
TO A POSSIBILITY OF A BRIEF PERIOD OF GALE FORCE WINDS OVER THE
CENTRAL STRAIT OF JUAN DE FUCA LATE TODAY OR EARLY THIS EVENING.
CONFIDENCE WAS NOT HIGH DUE TO DISAGREEMENT IN THE MODELS...SO
WILL KEEP THE FORECAST OF 20 TO 30 KT GOING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT TIL 5 AM SATURDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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