Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 011619
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
919 AM PDT SUN MAY 1 2016

.SYNOPSIS...HIGH PRESSURE ALOFT WILL BRING DRY AND WARMER WEATHER
THROUGH MONDAY. SOUTHERLY FLOW ALOFT AND LOW LEVEL ONSHORE FLOW
WILL RETURN TUESDAY AND PERSIST FOR MOST OF THE REST OF THE WEEK
FOR A CHANCE OF SHOWERS AND COOLER TEMPERATURES. AN UPPER RIDGE
WILL BRING DRIER AND WARMER WEATHER AGAIN LATE IN THE WEEK.

&&

.SHORT TERM...HIGH PRESSURE ALOFT WILL BRING SUNNY AND WARM
WEATHER THE NEXT COUPLE DAYS. AT THE SURFACE...A THERMAL TROUGH
WILL BUILD NORTH ALONG THE WEST COAST FOR INCREASING OFFSHORE
FLOW. THIS WILL ALLOW HIGHS TO WARM INTO THE 70S TODAY. THE
THERMAL TROUGH WILL SHIFT OVER THE INTERIOR OF WESTERN WASHINGTON
TUESDAY. THIS WILL TRANSLATE INTO MONDAY BEING THE WARMEST DAY FOR
THE INTERIOR...A FEW DEGREES WARMER THAN TODAY...WITH SOME COOLING
AT THE COAST WHERE ONSHORE FLOW WILL START TO DEVELOP.

AN UPPER TROUGH WILL MOVE TO NEAR 130W TUESDAY WITH INCREASING
MOIST AND SLIGHTLY UNSTABLE SOUTHERLY FLOW ALOFT FOR WESTERN
WASHINGTON. THIS WILL BRING A CHANCE OF SHOWERS. THE BEST CHANCES
WILL BE NEAR THE COAST AND OVER THE CASCADES. THERE WILL ALSO BE
A CHANCE OF AFTERNOON AND EVENING THUNDER FOR THE CASCADES WHERE
THE AIR WILL BE MORE UNSTABLE. INCREASING LOW LEVEL ONSHORE FLOW
WILL COOL HIGHS INTO THE 60S TO LOWER 70S. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...THE UPPER FLOW PATTERN WILL BE
SPLIT OVER THE WESTERN USA DURING THIS PERIOD. THE UPPER TROF
OFFSHORE ON TUESDAY WILL REMAIN OFF THE WEST COAST ON
WEDNESDAY...WITH MUCH OF THE ENERGY DIVING SOUTH TOWARDS THE CA
WATERS. EXPECT A CLOSED UPPER LOW ON THURSDAY OFF THE CA COAST.
THIS WILL PLACE WESTERN WA BETWEEN TROFS OVER CA AND BRITISH
COLUMBIA AND RIDGES OFFSHORE AND OVER THE ROCKIES.

BEYOND THURSDAY...THE UPPER LEVEL RIDGE OFFSHORE WILL BEGIN
BUILDING EAST OVER OUR AREA FOR A DECREASING THREAT OF SHOWERS AND
INCREASED SUNSHINE.

&&

.AVIATION...UPPER LEVEL RIDGE OFFSHORE WILL EVOLVE INTO A MUCH
STRONGER UPPER LEVEL RIDGE OVER WESTERN CANADA...WITH THE CENTER OF
HIGH PRESSURE OVER SOUTHERN BRITISH COLUMBIA. THIS WILL RESULT IN
NORTHEASTERLY FLOW ALOFT BECOMING MORE EASTERLY TODAY. LOW LEVEL
FLOW REMAINING OFFSHORE THROUGH TONIGHT.

WITH THE UPPER LEVEL RIDGE AND LOW LEVEL OFFSHORE FLOW JUST A FEW
HIGH CLOUDS OVER THE AREA THROUGH MONDAY.

KSEA...SOME HIGH CLOUDS AT TIMES. NORTHERLY WINDS 4 TO 8 KNOTS
INCREASING TO 8 TO 12 KNOTS MOD AFTERNOON. WINDS EASING AND BECOMING
NORTHEAST AFTER 05Z. FELTON

&&

.MARINE...LOW LEVEL OFFSHORE FLOW TODAY WITH THERMALLY INDUCED
TROUGH ALONG THE COAST. A RETURN TO LOW LEVEL ONSHORE FLOW WILL
OCCUR LATER MONDAY INTO TUESDAY WITH VARYING DEGREES OF ONSHORE FLOW
THROUGH THE END OF THE WEEK. FELTON

&&

.CLIMATE...APRIL 2016 WAS THE WARMEST APRIL ON RECORD ACROSS
WESTERN WASHINGTON. APRIL 2016 TEMPERATURES CRUSHED THE OLD RECORD
TEMPERATURES BY 1.5 DEGREES TO A LITTLE MORE THAN 3 DEGREES.
SEATTLE HAD THE BIGGEST DIFFERENCE WITH 56.7 DEGREES VERSUS THE OLD
RECORD OF 53.6 DEGREES SET IN 1977. OTHER RECORDS INCLUDE
BUT ARE NOT LIMITED TO...OLYMPIA 53.2...OLD RECORD 50.9
(1989)...BELLINGHAM 54.0...OLD RECORD 52.0 (1989)...HOQUIAM 53.8
DEGREES...OLD RECORD 52.3 (1987) AND QUILLAYUTE 51.9 DEGREES...OLD
RECORD 50.3 (1989). FELTON

&&

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

$$

WWW.WEATHER.GOV/SEATTLE

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


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