High Wind in Washington, December 22, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
331 PM PST TUE DEC 22 2015

.SYNOPSIS...A LOW PRESSURE SYSTEM OFFSHORE WILL CONTINUE MOVING
EAST. THIS SYSTEM WILL IMPACT THE REGION TONIGHT FOR MORE LOCALLY
HEAVY SNOW IN THE MOUNTAINS. AN UPPER LEVEL DISTURBANCE WILL
IMPACT THE AREA DURING THE DAY WEDNESDAY FOR ANOTHER ROUND OF
LOCALLY HEAVY SNOW IN THE MOUNTAINS. LOOK FOR A COLD LOW PRESSURE
SYSTEM ALOFT TO SETTLE OVER THE REGION ON THURSDAY.

&&

.SHORT TERM...
PRECIP WAS OVERSPREADING THE CWA FROM THE WEST AHEAD OF AN
OCCLUDED FRONT AT THIS TIME. EXPECT THE PRECIP TO REACH THE REST
OF THE CWA BY MIDNIGHT TONIGHT. THE NEGATIVE TILTED UPPER LEVEL
TROF AND ASSOCIATED OCCLUDED FRONT WILL SWEEP ACROSS THE REGION
LATE TONIGHT. ANTICIPATE STRONG ONSHORE FLOW TO DEVELOP IN THE
WAKE OPF THE FRONT...RESULTING IN LOCALLY WINDY
CONDITIONS...ESPECIALLY OVER THE COAST.

ANOTHER UPER LEVEL TROF WILL APPROACH THE CWA DURING THE DAY WED.
THE MAIN IMPACT THIS SYSTEM WILL HAVE ON OUR WEATHER WILL BE TO
JKEEP CONDITIONS COOL...WET...AND UNSETTLED. IN GENERAL...IT
LOOKED LIKE THE HEAVIEST SNOW WILL OCCUR DURING THE DAY WED AS
OPPOSED TO TONIGHT. THE ONSHORE SURFACE PRESSURE GRADIENT WILL
REMAIN STRONG FOR LOCALLY WINDY CONDITIONS.

THE UPPER TROF WILL MOVE ACROSS THE AREA WED NIGHT FOR MORE SNOW
IN THE MOUNTAINS. AMOUNTS ARE EXPECTED TO BE MAINLY IN THE ADVISRY
CRITERIOR RANGE /6 TO 11 INCHES/ IN THE CASCADES WITH LESSER
AMOUNTS ON THE OLYMPICS.

ANTICIPATE THE UPPER LEVE TROF TO DIG SOUTHWARD OVER THE WESTERN
USA DURING THE DAY THU. MUCH OF THE ENERGY AND DEEP LAYERED
MOISTURE WILL BE WELL SOUTH OF THE AREA. IN OTHER WORDS...EXPECT
SCATTERED /MAINLY LIGHT/ SHOWERS OVER THE CWA ON THU.

THE UPPER TROF WILL MOVE EAST OF THE REGION ON CHRISTMAS DAY...
LEAVING THE CWA UNDER DRIER...COLD NRTHERLY FLOW. ANY PRECIP
ON CHRISTMAS SHOULD BE LIGHT AND SPOTTY.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS LOW DUE TO DISAGREEEMT BETWEEN THE
MEDIUM RANGE SOLUTIONS. COMPROMISED BETWEEN THEGFS AND ECMWF
SOLUTIONS.

&&

.AVIATION...WESTERLY FLOW ALOFT OVER WA TO CONTINUE INTO WEDNESDAY.
AN UPPER LEVEL TROUGH EMBEDDED IN THE FLOW WILL FOLLOW A PACIFIC
FRONTAL SYSTEM EXPECTED TO MOVE ONSHORE WITH RAIN THIS EVENING. THE
AIR MASS TO REMAIN FAIRLY MOIST AT ALL LEVELS AND BECOME MORE
UNSTABLE FOLLOWING THE FRONTAL SYSTEM TONIGHT.

A COMBINATION OF LOW END VFR AND IN A FEW LOCATIONS - MVFR CEILINGS
FOR THE REMAINDER OF THE AFTERNOON. THE INCOMING FRONTAL SYSTEM
SHOULD BE A QUICK MOVER. EXPECT MVFR CEILINGS WITH THE FRONT THIS
EVENING. THEN SHOWERS WITH PRIMARILY MVFR CEILINGS WELL INTO
WEDNESDAY. SOUTH OR SW WINDS TO PICK UP BEHIND THE FRONT AS WELL -
MOST AREAS IN THE 15 TO 25 KT RANGE THOUGH TO 35 KT IN PARTS OF THE
COAST AND NORTH INTERIOR.

KSEA...CEILINGS AROUND 035-040 UNTIL THE FRONT ARRIVES NEAR 00-03Z
WITH CEILINGS DROPPING TO MVFR 015-020. RAIN WITH THE FRONT TURNING
TO SHOWERS NEAR 06Z. MVFR CEILINGS WITH SHOWERS THOUGH COULD GET A
BREAK IN THE CLOUD COVER AT TIMES WELL INTO WEDNESDAY. SURFACE WINDS
SOUTHERLY 10-15 KT BECOMING SW 15-20 KT POST-FRONTAL. BUEHNER

&&

.MARINE...AT 18Z...A PACIFIC FRONTAL SYSTEM WAS ABOUT 150NM OFF THE
COAST AND WILL QUICKLY MOVE ONSHORE AND INLAND THIS EVENING. STRONG
NW FLOW IS EXPECTED BEHIND THE FRONT FOR GALE FORCE WINDS OVER THE
COASTAL WATERS AND LIKELY WESTERLY GALES IN THE STRAIT. SMALL CRAFT
ADVISORY WINDS ALL OTHER WATERS WITH AND BEHIND THE FRONT.

THE FRONTAL SYSTEMS ASSOCIATED LOW PRES SYSTEM NOW ABOUT 300 NM OF
CAPE SCOTT MIDDAY IS EXPECTED TO MOVE SE THROUGH THURSDAY MORNING
AND PLAY A ROLE IN THE GALE FORCE WINDS BY KEEPING THE ISOBARS
TIGHT. YET BY THURSDAY AND FRIDAY AS THE LOW CONTINUES TO DRIFT
SE...THE LOW IS ANTICIPATED TO WEAKEN.

THE STRONG NW FLOW IS GENERATING A GOOD WESTERLY SWELL FETCH OF 20
TO 25 FT THAT WILL REACH THE COASTLINE TONIGHT AND PEAK LATER
WEDNESDAY. THE HEAVY SWELLS SHOULD SLOWLY SUBSIDE THROUGH WEDNESDAY
NIGHT AND THURSDAY. CONFIDENCE IS HIGH THAT THE SWELL WILL REACH 20-
25 FEET BUT IT COULD PEAK A LITTLE HIGHER. A HIGH SURF ADVISORY IS
IN PLACE.

IN ADDITION...SEASONAL HIGH TIDES CONTINUE. THE HIGH TIDE ON THE
COAST WEDNESDAY WILL COINCIDE WITH THE LARGE W SWELL...CREATING THE
LIKELIHOOD OF SOME COASTAL FLOODING. WILL UPDATE THE COASTAL FLOOD
WATCH TO A WARNING FOR THE CENTRAL COAST INCLUDING THE GRAYS HARBOR
AREA. BUEHNER

&&

.HYDROLOGY...
RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING UNTIL 6 PM PST WEDNESDAY FOR CASCADES
     OF PIERCE AND LEWIS COUNTIES-CASCADES OF SNOHOMISH AND KING
     COUNTIES.

     WINTER WEATHER ADVISORY UNTIL 6 PM PST WEDNESDAY FOR CASCADES
     OF WHATCOM AND SKAGIT COUNTIES AND THE OLYMPICS.

     COASTAL FLOOD WARNING FROM 8 AM TO 2 PM PST WEDNESDAY FOR
	 THE CENTRAL COAST.

     HIGH SURF ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT PST
	 WEDNESDAY NIGHT FOR THE COAST.

     WIND ADVISORY FROM 10 PM THIS EVENING TO 4 PM PST WEDNESDAY
	 FOR THE COAST.

PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 4 AM PST THURSDAY
	 FOR THE GRAYS HARBOR BAR.

     GALE WARNINGS IN EFFECT FOR THE COASTAL WATERS AND STRAIT OF
	 JUAN DE FUCA.

     SMALL CRAFT ADVISORIES IN EFFECT FOR THE ADMIRALTY INLET...
     NORTHERN INLAND WATERS...AND PUGET SOUND/HOOD CANAL.

&&

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