High Wind Warning 15, NWS Seattle, WA

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SEATTLE WA
413 AM PST SAT DEC 4 2010

CORRECTED A COUPLE OF MINOR TYPOS.

.SYNOPSIS...HIGH PRESSURE ALOFT WILL DOMINATE THE WEATHER PATTERN
OVER THE AREA THROUGH MONDAY FOR GENERALLY DRY WEATHER. MEANWHILE...
STRENGTHENING...LOW LEVEL...OFFSHORE FLOW WILL RESULT IN AREAS OF
STRONG...GUSTY WINDS OVER THE EAST PUGET SOUND LOWLANDS THROUGH
SUNDAY.

&&

.SHORT TERM...
AN AMPLIFYING UPPER RIDGE WILL PREVAIL OVER THE REGION TODAY. THIS
RIDGE WILL SHIFT TO OVER THE INTERIOR W BY EARLY SUNDAY...ALLOWING
AN UPPER TROF OFFSHORE TO EDGE EVER SO CLOSER TO THE PAC NW. EXPECT
THE UPPER RIDGE TO SHIFT SLIGHTLY FARTHER EWD AND WEAKEN SOME BY MON
AS FLOW UNDERCUTS IT.

MEANWHILE...THE MAIN WEATHER STORY FOR OUR CWA WILL BE INCREASING
LOW LEVEL OFFSHORE OR ELY FLOW. THE WENATCHEE TO SEATTLE PRES
GRADIENT HAS BEEN RUNNING TIGHTER THAN WHAT THE MODELS PREDICTED AND
WAS CLOSE TO -7 MB AT THIS TIME. THE SFC PRES GRADIENT IS EXPECTED
TO TIGHTEN FURTHER THRU TONIGHT...THUS I FELT THAT IT WOULD BE
PRUDENT TO ISSUE A WIND ADVISORY FOR THE EAST PUGET SOUND LOWLANDS
FOR THIS AFTERNOON THRU LATE TONIGHT. THE MODELS INDICATED THAT THE
ELY GRADIENT WILL PEAK OR WILL BE AT ITS TIGHTEST LATE TONIGHT OR
EARLY SUNDAY. SINCE THE MODEL PRES GRADIENTS WERE WEAKER THAN
REALITY...FELT IT WOULD ALSO BE A GOOD IDEA TO ISSUE A HIGH WIND
WATCH FOR THE EAST PUGET SOUND LOWLANDS FROM LATE TONIGHT THRU
SUNDAY MORNING. EXPECT AREAS OF GUSTY E WINDS ACROSS THIS AREA TO
CONTINUE THRU SUNDAY NIGHT THOUGH.

AS FAR AS PRECIP WAS CONCERNED...THE MODELS WERE GENERALLY DRY...SO
WENT IN THAT DIRECTION...ESPECIALLY WITH LOW LEVEL EASTERLIES
ADVECTING DRIER AIR INTO THE LOWER LEVELS OF THE ATMOSPHERE. THE
BEST CHANE OF PRECIP WILL BE OVER THE MOUNTAINS DURING THIS PERIOD.

.LONG TERM...
CONFIDENCE IN THE DETAILS FOR THIS PERIOD WAS NOT HIGH. THE MAIN
MESSAGE WAS THAT THE WEATHER PATTERN WILL EVOLVE INTO A STORMIER AND
WETTER ONE FOR THE PAC NW. THERE IS A CHANCE OF SIGNIFICANT RAINFALL
ON THE S OR SW SLOPES OF THE OLYMPICS ABOUT THE MIDDLE OF THE
UPCOMING WEEK.

&&

.HYDROLOGY...
THERE IS LITTLE OR NO THREAT OF FLOODING PRIOR TO SATURDAY DECEMBER
11...WITH THE EXCEPTION OF THE SKOKOMISH RIVER.

A WETTER PATTERN WILL DEVELOP LATE MONDAY AND CONTINUE THROUGH NEXT
WEEK. HOWEVER IT IS NOT THE PATTERN THAT GENERALLY PRODUCES FLOODING
IN WESTERN WASHINGTON...AND IT SHOULD PRESENT A THREAT OF FLOODING
ONLY FOR THE SKOKOMISH RIVER.

THERE IS A CHANCE THE SKOKOMISH RIVER WILL FLOOD SOMETIME BETWEEN
TUESDAY AND FRIDAY. MOST OF THE LONGER RANGE MODELS SHOW MORE THAN
4 INCHES OF RAIN OVER THAT BASIN DURING THE 96 HOUR PERIOD FROM
MIDDAY MONDAY TO MIDDAY FRIDAY. THAT IS NOTHING EXTRAORDINARY FOR
THE SOUTH SLOPES OF THE OLYMPICS...BUT THE SKOKOMISH COULD FLOOD IF
A GOOD CHUNK OF THAT RAIN FALLS IN LESS THAN 48 HOURS. AT PRESENT...
TUESDAY THROUGH WEDNESDAY LOOKS LIKE THE WETTEST PERIOD. IT IS ALSO
POSSIBLE THAT THE ACCUMULATION OF THAT MUCH RAIN OVER 4 DAYS COULD
GRADUALLY DRIVE THE RIVER TO FLOOD STAGE LATE IN THE WEEK.

LOOKING FURTHER AHEAD...SOME GFS RUNS OVER THE PAST FEW DAYS HAVE
SHOWN A MUCH WETTER AND WARMER PATTERN DEVELOPING THE NIGHT OF
FRIDAY DECEMBER 10 AND NEXT WEEKEND -- QUITE SIMILAR TO THE CLASSIC
FLOOD-PRODUCING PATTERN. HOWEVER...IN GENERAL...THE MODELS APPEARED
TO BE LEANING TOWARD THE IDEA OF THE FOCUS OF THE HEAVIEST RAINS
OCCURING TO OUR S. AT ANY RATE...CONFIDENCE IN THE FORECAST THIS FAR
AHEAD IN THE FUTURE WAS LOW. MCDONNAL/SCHNEIDER/05

&&

.AVIATION...A WEAK UPPER RIDGE WILL REMAIN OVER THE AREA TODAY WHILE
LOW LEVEL OFFSHORE FLOW INCREASES. THIS HAS LIMITED STRATUS AND FOG
FORMATION OVERNIGHT...BOTH KOLM AND KPAE HAVE HAD OCCASIONAL LOW
CLOUDS BUT MOSTLY THEY HAVE BEEN CLEAR. NORTHERLY FLOW HAS ALSO
BROUGHT SOME CLOUDS ON THE NORTH SIDE OF THE OLYMPIC PENINSULA
INCLUDING KCLM. ELSEWHERE ANY STRATUS OR FOG THAT DOES DEVELOP
TONIGHT WILL BE QUICK TO BURN OFF THIS MORNING.

KSEA...NO FOG OR STRATUS EXPECTED AT THE TERMINAL TODAY AS
INCREASING NORTHEAST FLOW SHOULD KEEP THIS FROM FORMING. CHB

&&

.MARINE...OFFSHORE FLOW IS STRONG ENOUGH TO CAUSE SMALL CRAFT
ADVISORY WINDS AT TIMES TODAY THROUGH SUNDAY IN ALL THE COASTAL
ZONES AND IN THE CENTRAL AND WEST STRAIT. STRONGEST WINDS WILL BE
NEAR THE WEST ENTRANCE. EASTERLY WINDS COULD REACH GALE FORCE AROUND
THE WEST ENTRANCE LATE TONIGHT AND SUNDAY MORNING AT THE PEAK OF THE
OFFSHORE FLOW. WILL KEEP THE GALE WATCH GOING THERE.

MONDAY THROUGH WEDNESDAY WILL BE AN ACTIVE PERIOD WITH SEVERAL
FRONTS AND LOW PRESSURE SYSTEMS GRAZING THE REGION. OCCASIONAL GALES
ARE A GOOD BET OVER THE COASTAL WATERS AND PARTS OF THE INLAND
WATERS AT TIMES DURING THIS PERIOD. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY IN EFFECT FOR THE EAST PUGET SOUND LOWLANDS FROM
     NOON TODAY TIL MIDNIGHT TONIGHT.

     HIGH WIND WATCH IN EFFECT FOR THE EAST PUGET SOUND LOWLANDS
     FROM LATE TONIGHT THRU SUNDAY MORNING.

PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE WEST ENTRANCE TO THE
     STRAIT OF JUAN DE FUCA AND THE NEAR SHORE WATERS FROM CAPE
     FLATTERY TO JAMES ISLAND TIL 10 PM TONIGHT.

     GALE WATCH IN EFFECT FOR THE WEST ENTRANCE TO THE STRAIT OF
     JUAN DE FUCA AND THE NEAR SHORE WATERS FROM CAPE FLATTERY TO
     JAMES ISLAND FROM LATE TONIGHT THRU SUNDAY MORNING.

WWW.WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
759 AM PST SAT DEC 04 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0758 AM     NON-TSTM WND GST 4 WNW ENUMCLAW          47.23N 122.06W
12/04/2010  M66 MPH          KING               WA   TRAINED SPOTTER

            40 MPH WITH A PEAK GUST OF 66 MPH.

&&

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