Heavy Snow in Washington, November 11, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST FRI NOV 11 2011

.SYNOPSIS...A STRONG COLD FRONT WILL MOVE THROUGH WESTERN WASHINGTON
TODAY BRINGING WET AND WINDY CONDITIONS ALONG WITH MOUNTAIN SNOW.
WET AND BLUSTERY WEATHER WILL RETURN ON SAT AS ANOTHER SYSTEM
IMPACTS THE REGION. COOL AND SHOWERY WEATHER WILL CONTINUE SUNDAY
THROUGH MID WEEK AS A SERIES OF UPPER LEVEL DISTURBANCE CLIP THROUGH
WESTERN WASHINGTON.

&&

.SHORT TERM...A STRONG AUTUMN STORM WILL ROLL THROUGH WESTERN WA
TODAY BRINGING A PERIOD OF WET AND BLUSTERY WEATHER TO THE
REGION...A STARK CONTRAST FROM THE SUNNY AND BENIGN WEATHER
YESTERDAY.

THE MAIN IMPACTS WITH THIS SYSTEM ARE WIND AND MOUNTAIN SNOW. AS FOR
THE WINDS...WILL ISSUE A WIND ADVISORY FOR THE INTERIOR LOWLANDS AND
EASTERN STRAIT OF JUAN DE FUCA. SOUTH WINDS WILL RISE SHARPLY JUST
AHEAD OF THE COLD FRONT. SUSTAINED WINDS OF 20 TO 30 MPH WITH LOCAL
GUSTS TO 50 MPH ARE POSSIBLE /WINDS WILL BE WESTERLY THROUGH THE
STRAIT/. THE FLOW WILL THEN FLIP TO WEST/NORTHWESTERLY THIS
AFTERNOON AS THE FRONT QUICKLY PUSHES FARTHER INLAND THEN EXITS.
THIS IS A TYPICAL PATTERN FOR STRONG...POSSIBLY DAMAGING WINDS
THROUGH ADMIRALTY INLET...ESPECIALLY WHIDBEY ISLAND. THUS WILL ISSUE
A HIGH WIND WARNING FOR THE ADMIRALTY INLET AREA. WINDS WILL EASE
THIS EVENING ACROSS ALL ZONES...03-06Z.

IN ADDITION...THIS SYSTEM WILL DRAG A MUCH COOLER AIR MASS INLAND
WITH SNOW LEVELS LOWERING FROM AROUND 5000 FT THIS MORNING TO AROUND
2500 FEET THIS AFTERNOON. MOUNTAIN SNOW AMOUNTS MAY REACH WINTER
WEATHER ADVISORY CRITERIA...MAINLY THE VOLCANOES AND SKI AREAS. THE
PASSES MAY ONLY SEE A FEW INCHES. SNOW SHOWERS WILL TAPER DOWN THIS
EVENING.

ANY BREAK IN THE WEATHER WILL BE SHORT-LIVED AS THE MODELS SHOW
ANOTHER PAC SYSTEM IMPACTING W WA ON SAT. WINDS LOOK LIGHTER WITH
THIS NEXT SYSTEM...BUT MAY STILL SEE BREEZY CONDITIONS. THE BULK OF
THE ENERGY IS DIVING SOUTH OF THE CWA BUT THERE IS STILL PLENTY OF
MOISTURE TO WORK WITH. SNOW LEVELS WILL REMAIN NEAR 2000 FT AGL WITH
MORE ACCUMULATING SNOW POSSIBLE IN THE MOUNTAINS. MAY NEED TO HOIST
ANOTHER WINTER WEATHER ADVISORY.

THE PATTERN REMAINS ACTIVE THROUGH SUNDAY WITH STRONG NWLY FLOW
ALOFT...160 KT JET AIMED AT W WA. THUS MORE SHOWERS AND COOLER
WEATHER FOR THE REGION. 33

.LONG TERM...THERE IS LITTLE CHANGE IN THE WEATHER PATTERN ACROSS
THE PAC NW THROUGH MID WEEK. THE POLAR JET WILL RIDE ACROSS WESTERN
WA MAINTAINING AN ACTIVE WEATHER PATTERN. 500 MB HEIGHTS WILL REMAIN
IN THE 540S WITH SEVERAL UPPER LEVEL DISTURBANCES CLIPPING THROUGH
THE REGION. EXPECT A CONTINUATION OF COOL AND SHOWERY WEATHER WITH
SNOW LEVELS HOVERING BETWEEN 2000-3000FT. THE JET MAY DIP FARTHER
SOUTH AND INTO CA LATE IN THE WEEK AS A DEEP UPPER LEVEL LOW
DESCENDS FROM ALASKA. WILL MAINTAIN A PERSISTENCE FORECAST THAT
CALLS FOR BELOW NORMAL TEMPS AND ABOVE NORMAL PRECIPITATION. 33

&&

.HYDROLOGY...FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS. 33

&&

.AVIATION...A STRONG COLD FRONT OVER VANCOUVER ISLAND WILL MOVE SE
ACROSS WRN WA TODAY. MODERATE SW FLOW ALOFT WILL SWITCH TO VERY
STRONG NW FLOW BEHIND THE FRONT THIS AFTERNOON AND EVENING...THEN
EASING TONIGHT. STABLE CONDITIONS THIS MORNING AND BECOMING MOIST AT
ALL LEVELS. RAIN WILL OVERSPREAD THE AREA BY MID-LATE MORNING AND
BECOME SHOWERY BY FRI EVENING. THE AIR MASS WILL BECOME SOMEWHAT
UNSTABLE BEHIND THE FRONT LATE THIS AFTERNOON AND EVENING. THERE IS
A LOW PROBABILITY OF AN ISOLATED THUNDERSTORM.

ANY PATCHY FOR THIS MORNING WILL BREAK UP OVER THE NEXT FEW HOURS AS
SURFACE WINDS INCREASE. MID CLOUDS WILL QUICKLY INCREASE EARLY THIS
MORNING WITH AREAS OF MVFR 2-3K FT CIGS WITH THE FRONTAL RAINFALL IN
THE LATE MORNING AND AFTERNOON.

KSEA...SE WINDS 7-12 KT...BECOMING S AND RISING TO TO 15-25 KT W/
GUSTS 30 KT BY LATE MORNING. WINDS WILL BECOME SWLY EARLY THIS
AFTERNOON.

**A QUICK SWITCH TO NW WIND 9-13 KT IS EXPECTED AT THE KSEA TERMINAL
ROUGHLY BY 03Z THIS EVENING. WINDS WILL LIKELY NOT STAY NW FOR VERY
LONG...GOING BACK TO A SW WIND 5-10 KT BY 08Z. DTM

&&

.MARINE...THE COLD FRONT OVER VANCOUVER ISLAND WILL REACH THE
COASTAL WATERS THIS MORNING AND PUSH ACROSS THE INLAND WATERS AROUND
MIDDAY. LATEST MODEL DATA HAVE TRENDED SOMEWHAT STRONGER WITH THIS
FRONTAL SYSTEM MEANING WINDS MAY BE A BIT STRONGER THAN THE PREVIOUS
FORECAST PACKAGE. NOTE SOME SLIGHT ADJUSTMENTS UPWARD...ESPECIALLY
TO INCLUDE GALES IN PUGET SOUND TODAY.

STRONG S/SE PRESSURE GRADIENTS WILL QUICKLY DEVELOP THIS MORNING
GIVING A BRIEF PERIOD OF SLY GALE FORCE WINDS FOR THE INLAND WATERS
FROM MID-LATE MORNING. A STRONG SURGE OF WESTERLIES WILL FOLLOW THE
FRONT...PRODUCING HIGH END GALES IN THE CENTRAL STRAIT OF JUAN DE
FUCA...EAST ENTRANCE STRAIT... ADMIRALTY INLET...AND NORTHERN INLAND
WATERS. W WINDS 35 TO 45 KT ARE LIKELY. GALE FORCE SWLY WINDS WILL
PERSIST IN PUGET SOUND THROUGH THE EARLY EVENING HOURS BEFORE
EASING. EXPECT THE NW WIND SURGE TO POSSIBLY REACH THE NRN HALF OF
THE PUGET SOUND WATERS THIS EVENING.

THE WINDS WILL PRODUCE WAVES OF 7-10 FEET AFFECTING THE EASTERN
PORTION OF THE STRAIT...WHIDBEY ISLAND...AND THE ADMIRALTY INLET
AREA. A MODERATELY HIGH TIDE WILL OCCUR THERE IN THE LATE
AFTERNOON...AND THE COMBINATION OF WIND WAVES AND TIDE COULD PRODUCE
MINOR COASTAL FLOODING. A COASTAL FLOOD ADVISORY IS IN EFFECT FOR
THE ADMIRALTY INLET AREA ZONE...FOCUSING ON THE WEST SIDE OF WHIDBEY
ISLAND. A MORE REMOTE POSSIBILITY IS WAVES ASSOCIATED WITH STRONG
NORTHWESTERLIES IN THE SOUTH END OF GEORGIA STRAIT AFFECTING
VULNERABLE SPOTS LIKE SANDY POINT. THAT EVENT LOOKS UNLIKELY BUT IT
WILL STILL BEAR WATCHING.

AN ACTIVE PATTERN WILL CONTINUE THIS WEEKEND AND EARLY NEXT WEEK...
WITH ADDITIONAL FRONTAL SYSTEMS PROBABLY MOVING THROUGH SATURDAY AND
SATURDAY NIGHT AND AGAIN SUNDAY NIGHT AND MONDAY. THESE SYSTEMS WILL
PROBABLY PRODUCE WINDS IN THE HIGH END SMALL CRAFT ADVISORY OR LOW
END GALE RANGE.  DTM/MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNING ADMIRALTY INLET AREA.
     WIND ADVISORY INTERIOR LOWLANDS AND EASTERN STRAIT OF JUAN DE
     FUCA.
     WINTER WEATHER ADVISORY OLYMPICS AND CASCADES.
     COASTAL FLOOD ADVISORY FRIDAY AFTERNOON ADMIRALTY INLET AREA.

PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE
     FUCA...ADMIRALTY INLET...NORTHERN INLAND WATERS...AND PUGET
     SOUND/HOOD CANAL.

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