High Wind in Washington, November 12, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
315 AM PST MON NOV 12 2007

.SYNOPSIS...A RAPIDLY DEEPENING AREA OF LOW PRESSURE AREA ABOUT 250
MILES WEST OF THE NORTHERN WASHINGTON COAST EARLY THIS MORNING WILL
MOVE INTO CENTRAL VANCOUVER ISLAND BY LATE THIS MORNING. THE FRONT
ASSOCIATED WITH THE LOW WILL REACH THE WASHINGTON COAST LATE THIS
MORNING THEN SWEEP THROUGH THE INTERIOR DURING THE EARLY AFTERNOON
HOURS. STRONG WINDS ARE EXPECTED AHEAD AND WITH THE FRONT ALONG THE
COAST AND OVER THE NORTHWEST INTERIOR...WITH STRONG WINDS POSSIBLE
OVER THE REMAINDER OF THE LOWLANDS WITH AND JUST AFTER THE FRONT.
THE UNSETTLED PATTERN WILL CONTINUE INTO NEXT WEEKEND KEEPING THE
THREAT OF RAIN IN THE FORECAST.

&&

.SHORT TERM...THE DEEPENING SURFACE LOW OFFSHORE CONTINUES TO PUT UP
SOME IMPRESSIVE NUMBERS. BUOY 5 REPORTED A PRESSURE DROP OF 10
MILLIBARS IN 3 HOURS EARLIER TONIGHT. THE NAM12 APPEARS TO HAVE
ABOUT THE BEST HANDLE ON THE STRENGTH OF THE LOW AS IT MOVES THROUGH
THE OFFSHORE WATERS. ALTHOUGH...BASED ON BUOY AND OTHER MARITIME
OBS...THE LOW MAY BE ABOUT 3 TO 5 MILLIBARS DEEPER THAN ANY MODEL
HAD IT. A NUMBER OF OFFSHORE AIRCRAFT OBS REPORTED JET STREAM WINDS
IN THE 180-190 KT RANGE EARLIER TODAY...SO IT COMES AS NO REAL
SURPRISE THAT THIS SYSTEM IS GETTING PLENTY OF UPPER LEVEL SUPPORT.
A NUMBER OF COASTAL OBS HAVE BEEN REPORTING EERILY LIGHT EASTERLY
WIND OVER THE PAST 3 OR 4 HOURS...A TRUE CALM BEFORE THE STORM. AS
THE LOW PROGRESSES NORTHEASTWARD THIS MORNING...SOUTHERLY COASTAL
WINDS SHOULD RAPIDLY INCREASE AND BECOME QUITE STRONG. WINDS OVER
THE NORTH INTERIOR SHOULD ONCE AGAIN INCREASE BY MID MORNING. FOR
THAT REASON...WE WILL KEEP THE CURRENT HIGH WIND WARNINGS GOING AS
THEY ARE FOR THOSE AREAS.

ANALYSIS OF THE NAM12 AND MM5GFS RUNS FROM 00Z GIVES SOME REASON FOR
CONCERN OVER THE PUGET SOUND AREA. THE NAM12 FORMS A SURFACE MESOLOW
ON THE LEE SIDE OF THE OLYMPICS BY 18Z. THIS GENERATES QUITE A
PRESSURE GRADIENT...10 MILLIBARS OVER A DISTANCE OF 75 MILES.
COMBINE THIS WITH A POSSIBLE POST-FRONTAL PRESSURE RISE OF 9
MILLIBARS IN 3 HOURS AND MM5 925 MILLIBAR WINDS AROUND 55
KNOTS...AND WE HAVE DECIDED TO UPGRADE THE HIGH WIND WATCH TO A HIGH
WIND WARNING FOR THE GREATER PUGET SOUND AREA. THE WATCH OVER THE
SOUTHWEST INTERIOR WILL LIKELY BE CONVERTED TO A WIND ADVISORY.
SHORT DURATION QPF IS PRETTY IMPRESSIVE WITH THE SYSTEM AS
WELL...BUT THE SPEED OF THE SYSTEM SHOULD PREVENT ANY CONCERNS OF
THAT REGARD. RAIN TURNS TO SHOWERS AND WINDS WILL DECREASE LATER
THIS AFTERNOON BEHIND THE FRONT. SNOW LEVELS WILL FALL A COUPLE
THOUSAND FEET BEHIND THE FRONT...WITH A FEW INCHES OF SNOW POSSIBLE
DOWN TO SOME PASS LEVELS OVERNIGHT TONIGHT.

SHOWERS ACTIVITY ACROSS THE REGION GRADUALLY TAPERS OFF ON TUESDAY
AS UPPER LEVEL RIDGING NOSES INTO THE AREA. DRIER CONDITIONS ARE
EXPECTED LATER TUESDAY AND TUESDAY TONIGHT...BEFORE ANOTHER SYSTEM
SPREADS MORE PRECIP INTO THE AREA DURING THE DAY ON WEDNESDAY.

.LONG TERM...NO CHANGES WERE MADE TO EXTENDED FORECAST AT THIS TIME.
WHILE THE EXTENDED MODELS HAVE SOME MINOR DIFFERENCES AMONGST
THEMSELVES...THEY GENERALLY AGREE THAT THE STORM TRACK REMAINS AIMED
AT THE PACIFIC NORTHWEST WITH SEVERAL SYSTEMS AFFECTING THE AREA
THOUGH THE WEEKEND. NOVEMBER AT ITS FINEST. 27

&&

.AVIATION...CEILINGS ARE GENERALLY VFR AT THIS TIME WITH A SCT-BKN
LAYER AROUND 5000 FT AND A BKN-OVC LAYER AROUND 11000 FT...AND IN
FACT THEY HAVE FALLEN LITTLE SO FAR SINCE SUN EVENING. CEILINGS
ALONG THE NORTH COAST REMAIN MVFR. CONDITIONS WILL DETERIORATE TO
MVFR AND LOCAL IFR FOR A FEW HOURS AS THE FRONT MOVES THROUGH. IT
WILL MAKE LANDFALL ON THE COAST AROUND 19Z AND MOVE THROUGH THE
PUGET SOUND AREA AROUND 21Z...QUICKLY HEADING EAST OF THE CASCADES
BY 00Z TUE. OF COURSE...THE WIND WILL BE THE BIG STORY WITH THIS
FRONT. SUSTAINED WINDS ALONG THE COAST AND IN THE NORTH INTERIOR
WILL BE 40 TO 50 MPH WITH GUSTS TO 70 MPH...AND THE PUGET SOUND
REGION -- WHICH IS CURRENTLY EXPERIENCING THE CALM BEFORE THE STORM
-- WILL REACH 30 TO 40 MPH SUSTAINED WITH GUSTS TO 60 MPH. I WILL
ADD LLWS GROUP TO MOST OR ALL TAFS WITH THE 12Z ISSUANCE. MCDONNAL

.KSEA...LIKE MOST SPOTS IN THE PUGET SOUND AREA...WINDS AT KSEA HAVE
EASED SOMEWHAT OVERNIGHT DUE TO THE TRACK OF THE APPROACHING LOW.
HOWEVER THIS IS ONLY THE CALM BEFORE THE STORM. SOUTHEAST WIND WILL
RISE TO 12-20 KT GUSTING 30 KT BY AROUND 16Z...THEN BECOME SOUTHWEST
18-26 KT WITH GUSTS AS HIGH AS 40 KT BEGINNING 20Z OR SO. THE WIND
WILL PROBABLY BE STRONGEST RIGHT WITH OR JUST AFTER THE FRONT EARLY
THIS AFTERNOON. MCDONNAL

&&

.MARINE...THE STRONG FRONT MOVING THROUGH THE FORECAST AREA TODAY
WILL PRODUCE GALE TO STORM FORCE WINDS OVER THE MARINE WATERS. I
NOTCHED WINDS UP A BIT OVER MOST OF THE INLAND WATERS...SO WE WILL
HAVE A STORM WARNING FOR THE COASTAL WATERS...ENTRANCES TO THE
STRAIT...ADMIRALTY INLET AND NORTHERN INLAND WATERS. THE FRONT WILL
REACH THE COAST AROUND 19Z AND MOVE THROUGH THE INTERIOR OF WRN WA
BY 22Z. IN ADDITION THERE WILL BE A SURGE OF GALE FORE WESTERLIES
DOWN THE STRAIT OF JUAN DE FUCA BEHIND THE FRONT. THE PUGET SOUND
WATERS ARE LIKELY TO SEE THE STRONGEST GALES WITH OR JUST AFTER THE
FRONT THIS AFTERNOON. SWELLS WILL BUILD TO AROUND 20 FT EARLY MON
MORNING AND EVENTUALLY TO AROUND 24 FT MON AFTERNOON -- RESULTING IN
HAZARDOUS SEAS...SEVERE BAR CONDITIONS AT GRAYS HARBOR...AND HIGH
SURF ON THE COAST. MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
    .HIGH WIND WARNING FOR NW INTERIOR...COAST...AND GREATER PUGET
     SOUND AREA.
    .WIND ADVISORY FOR THE SOUTHWEST INTERIOR.
    .STORM WARNING COAST...ENTRANCES TO THE STRAIT...ADMIRALTY INLET
     ...NORTHERN INLAND WATERS.
    .GALE WARNING ALL CENTRAL STRAIT...PUGET SOUND AND HOOD CANAL.
    .HIGH SURF ADVISORY COASTAL ZONES.
    .SMALL CRAFT ADVISORY FOR SEVERE BAR CONDITIONS GRAYS HARBOR.

WEATHER.GOV/SEATTLE