High Wind and Strong Wind in Washington, November 15 to 16, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
355 PM PST SUN NOV 15 2009

.SYNOPSIS...A SERIES OF VIGOROUS STORM SYSTEMS WILL MOVE ACROSS
WESTERN WASHINGTON TONIGHT THROUGH TUESDAY. HEAVY RAIN WILL FALL IN
THE OLYMPICS AND IN THE NORTH CASCADES. HIGH WINDS WILL ALSO AFFECT
MUCH OF WESTERN WASHINGTON AT TIMES. ANOTHER STRONG FRONTAL SYSTEM
WILL ARRIVE WEDNESDAY NIGHT OR THURSDAY. THE WEATHER PATTERN WILL
REMAIN ACTIVE INTO NEXT WEEKEND.

&&

.SHORT TERM...A VERY ACTIVE WEATHER PERIOD IS EXPECTED ACROSS
WESTERN WASHINGTON OVER THE NEXT COUPLE DAYS WITH PERIODS OF HEAVY
RAIN AND HIGH WINDS. THE OVERALL MODEL TRENDS TODAY HAS BEEN TOWARD
FASTER AND STRONGER SOLUTIONS IN REGARDS TO WIND AND HEAVY RAIN. THE
FIRST WAVE TO AFFECT THE AREA BEGINS TO DEVELOP OFF THE WA COAST
THIS EVENING AND MOVES INLAND JUST OFF TATOOSH ISLAND AS A SUB 1000
MB LOW AFTER 09Z TONIGHT. THE WINDS ALOFT ALONG THIS INITIAL FRONTAL
BAND WILL BE VERY STRONG WITH 925 MB WINDS AROUND 70 KT ON THE COAST
AND AND 60 KT INLAND. THE 4KM MM5GFS TRANSLATES THIS TO A WIDE AREA
OF 35-40 KT OVER THE NORTH INTERIOR BY 06Z TONIGHT FROM ROUGHLY
WHIDBEY ISLAND NWD. WINDS ARE EVEN STRONGER ON THE COAST WITH STORM
FORCE CONDITIONS OVER THE WATERS AND SUSTAINED WINDS 40-45 KT ALONG
THE COAST. THE 925 MB FLOW COULD SURFACE AT TIMES CREATING HIGHER
GUSTS AS WELL. WILL ISSUE A HIGH WIND WARNING FOR ALL THESE AREAS
BEGINNING TONIGHT. THE REMAINDER OF WESTERN WASHINGTON WILL BE
BLANKETED WITH A WIND ADVISORY THROUGH MONDAY. THERE WILL BE A
COUPLE MORE BATCHES OF WIND TO CONTEND WITH BEYOND TONIGHT AND
MONDAY. ANOTHER WARM FRONT LIFTING ACROSS THE AREA MONDAY NIGHT
AHEAD OF A MUCH STRONGER SURFACE LOW EXPECTED TO DEVELOP. MODELS
DEVELOP INCREDIBLY STRONG 850 MB FLOW OF 85-100 KT ALONG THE OREGON
AND S/CENTRAL WA COAST...AND EVEN 80-85 KT DOWN TO 925 MB. THE 925
MB FLOW ACROSS THE INTERIOR REACHES 60 KT BY MONDAY NIGHT WITH THE
POSSIBILITY THAT THIS COULD SURFACE AS GUSTS AT TIMES. HIGH WINDS
APPEAR LIKELY ACROSS ALL OF WESTERN WASHINGTON...STRONGEST COAST AND
NORTH AND PROBABLY VERIFYING AS GUSTS FROM AROUND SEATTLE SOUTHWARD.
THE BENT BACK OCCLUSION LIFTS ACROSS THE AREA TUESDAY MORNING WITH
THE POSSIBILITY FOR MORE HIGH WIND JUST ABOUT EVERYWHERE. THE 18Z
GFS/NAM AS SLIGHTLY WEAKER WITH THE BENT BACK BUT OTHER RUNS SHOWED
AS MUCH AS +16 MB KPDX-KBLI. A HIGH WIND WATCH WILL BE ISSUED FOR
THE REST OF WESTERN WASHINGTON OUTSIDE THE CURRENT WARNING FOR
MONDAY NIGHT THROUGH TUESDAY MORNING.

AS FOR FLOODING...HEAVY RAIN WILL DEVELOP IN THE OLYMPICS AND NORTH
CASCADES TONIGHT PER THE LATEST 12/18Z MODEL RUNS. THE FRONTAL BAND
IS NOW EXPECTED TO STALL ACROSS THE NRN PORTION OF THE FORECAST AREA
TONIGHT THROUGH MONDAY MORNING...BEFORE MEANDERING A BIT MONDAY
AFTERNOON. RAINFALL RATES OF 2+ INCHES PER 6 HOURS ARE DEPICTED BY
THE LATEST 18Z NAM-12 AND NEARLY THAT OVER THE NORTH CASCADES. THE
HEAVIEST PRECIP WILL LIKELY OCCUR LATER TONIGHT THROUGH MONDAY
MORNING. THE FLOOD WATCH WAS EXPENDED EARLIER TO ALL RIVER BASINS
NORTH OF STEVENS PASS...WHICH IS GOOD BASED ON THE LATEST 18Z RUN.
THE 4KM MM5 IS STILL SHOWING 24 HOUR TOTALS OF 12+ INCHES OVER THE
OLYMPICS AND 5 TO 10 INCHES IN THE NORTH CASCADES. THIS IS MUCH
HIGHER THAN PREVIOUSLY EXPECTED GIVEN THAT THE FRONTAL BAND WILL
HANG UP FURTHER SOUTH DIRECTLY OVER THE OLYMPICS/N CASCADES AND ALSO
THE FLOW ALOFT IS COMING IN MUCH STRONGER ON THE MODELS INCREASING
OROGRAPHICS. SEE THE LATEST HYDROLOGY SECTION BELOW FOR MORE DETAILS
ON THE EXPECTED FLOODING.

ONCE THE LOW PASSES TUESDAY NIGHT WINDS WILL START TO EASE AND RAIN
WILL TAPPER TO SHOWERS. MUCH COOLER AIR WILL ARRIVE DROPPING SNOW
LEVELS DOWN TO 2500 FEET RESULTING IN SOME SNOW IN MOST THE PASSES.
THE FLOW AT THIS POINT IS NOT VERY STRONG AND STILL MORE SLY THAN
WLY SO ACCUMULATIONS IN THE PASSES WILL BE ON THE LIGHT SIDE.
SHOWERS CONTINUE INTO WEDNESDAY AS THE NEXT WARM FRONT APPROACHES
THE AREA. RAIN WILL BEGIN SPREADING BACK INTO WESTERN WASHINGTON AS
EARLY AS WEDNESDAY AFTERNOON.

.LONG TERM...THE NEXT STRONG SYSTEM WILL AFFECT WESTERN WASHINGTON
WEDNESDAY NIGHT THROUGH THURSDAY. MODELS SHOW THIS SYSTEM TO BE MORE
PROGRESSIVE THAN THE ONE CURRENTLY AFFECTING THE AREA. THIS WILL
HELP LIMIT QPF AMOUNTS BUT RAIN AND LOCALLY WINDY CONDITIONS WILLS
STILL DEVELOP ACROSS THE AREA. THE PATTERN BECOMES MORE UNCERTAIN
BEHIND THE FRONT FRIDAY INTO THE WEEKEND. BUT MODELS GENERALLY SHOW
A COOL AND SHOWERY PATTERN INTO THE WEEKEND.

&&

.HYDROLOGY...THE MAJORITY OF MESO MODEL RUNS ARE CONTINUING TO PUT
DOWN 10-12+ INCHES ACROSS THE OLYMPICS OVER THE 24 HOUR PERIOD
BEGINNING THIS EVENING. MODELS HAVE ALSO TRENDED TOWARD HIGHER
AMOUNTS ACROSS THE NORTH CASCADES WITH AMOUNTS OF 4 TO 9 INCHES
DEPENDING ON THE MODEL. THE 4KM MM5 SHOWS THE HIGHEST AMOUNTS WITH
THE COURSER GFS40/ECMWF SHOWS LIGHTER AMOUNTS...NO SURPRISE. THE
FLOOD WATCH STILL COVERS THE ENTIRE OLYMPIC PENINSULA AND RIVER
BASINS NORTH OF STEVENS PASS. THE SKOKOMISH RIVER WILL LIKELY BE THE
FIRST TO REACH FLOOD STAGE PROBABLY SOMETIME EARLY MONDAY
MORNING...POSSIBLY EVEN REACHING MAJOR FLOOD STAGE. OTHER RIVERS IN
THE OLYMPIC BASIN COULD REACH FLOOD STAGE LATER ON MONDAY. LATEST
HYDRO MODELS NOW SHOW FLOODING ON THE NOOKSACK AND STILLAGUAMISH
RIVERS...WITH OTHER RIVERS INDICATED TO REACH CLOSE TO FLOOD. WITH
THE VERY STRONG FLOW INDICATED BY MODELS THE HIGHER RAIN AMOUNTS ARE
CERTAINLY POSSIBLE. ALL RIVERS IN THE OLYMPIC AND NORTH CASCADE
RIVERS BASINS ARE AT RISK OF FLOODING THROUGH WEDNESDAY.

RAINFALL AMOUNTS WILL BE MUCH LESS OVER THE CENTRAL CASCADES.
HOWEVER...MODELS HAVE TRENDED HIGHER WITH 24 HOUR RAINFALL AMOUNTS
OF 2 TO 5 INCHES EXPECTED ALONG THE SW FACING SLOPES...AND MUCH LESS
AMOUNTS IN THE PASSES AND OTHER SLOPES. HYDRO MODELS SHOW MINOR
RISES ON SOME RIVERS BUT NOT TO BANKFULL...AND FLOODING IS NOT
CURRENTLY INDICATED FOR ANY RIVER. FORECASTS SHOULD BE MONITORED
CLOSELY OVER THE NEXT COUPLE DAYS. FLOODING IS NOT EXPECTED ON THE
GREEN RIVER OVER THE NEXT WEEK.

THE 4KM MM5 IS ALSO SHOWING SOME RATHER IMPRESSIVE RAINFALL TOTALS
ACROSS SOME OF THE LOWLAND AREAS NOT SHADOWED THROUGH MOST THE
EVENT. IF THE 4KM MODEL IS RIGHT...LOWLANDS ALONG THE METRO CORRIDOR
FROM EVERETT SOUTHWARD COULD RECEIVE 24 HOUR TOTALS OF 2 TO 5
INCHES. THIS MODEL ALSO SHOWS A 3-6 HOUR WINDOW OF VERY HEAVY
RAINFALL EXCEEDING 2 INCHES ON MONDAY WHICH COULD RESULT IN URBAN
AND SMALL STREAM FLOODING. HOWEVER..ALL OTHER MODELS SHOW MUCH LESS
PRECIP INCLUDING THE NAM-12 WHICH IS MORE ON THE ORDER OF 1 TO 2
INCHES. THIS IS THE FIRST SOLUTION I HAVE SEEN SHOWING THIS MUCH
LOWLAND PRECIP SO I WILL NOT ISSUE A WATCH AT THIS TIME. IF THE NEXT
ROUND OF MODEL RUNS SHOW THIS HIGHER QPF THEN A WATCH MAY NEED TO BE
CONSIDERED. PONDING OF WATER ON STREETS CAN EASILY BECOME A PROBLEM
THIS TIME OF YEAR WITH LOSS OF FOLIAGE...ESPECIALLY GIVEN THE WINDY
WEATHER EXPECTED. MERCER

&&

.AVIATION...A WARM FRONT BROUGHT SPOTTY PRECIPITATION TO THE PUGET
SOUND AREA TODAY...THOUGH RAIN ON THE NORTH COAST AND SOUTHERN
OLYMPIC PENINSULA HAS BEEN MUCH HEAVIER. WHILE THE RAINFALL PATTERN
WILL REMAIN UNCHANGED TONIGHT...SURFACE PRESSURE GRADIENTS WILL
INCREASE SIGNIFICANTLY. THIS WILL BRING STRONG SURFACE WINDS TO THE
COAST AND NORTH INLAND AREA TONIGHT AND MONDAY.

CEILINGS HAVE BEEN MOSTLY MVFR...OVC020-030...EXCEPT WHEN IT IS
RAINING...WHEN CEILINGS DIP TO OVC005-015 AND VISIBILITY FALLS TO
3-5SM IN MIST. WINDS ALOFT ARE STRONG AND REMAIN SO THROUGH MONDAY.
EXPECT 50-60 KT S/SW FLOW AT 5000 FT TO DEVELOP THIS EVENING. BY
MONDAY MORNING 50 KT SLY FLOW IS POSSIBLE BELOW 2000 FEET. SOME
AREAS...NOTABLY SEATTLE SOUTHWARD...COULD HAVE LLWS PROBLEMS BEFORE
THE WIND MIXES DOWN TO THE SURFACE.

KSEA...SOUTHERLY WIND 7-14 KT TONIGHT. S WIND WILL RISE TO 20G30KT
DURING THE DAY ON MONDAY. LIGHT RAIN AT TIMES TONIGHT...POSSIBLE
PERIODS OF MODERATE RAIN MONDAY. BURKE

&&

.MARINE...A DEVELOPING WAVE OF LOW PRESSURE MOVING THROUGH THE
OFFSHORE WATERS AND INTO VANCOUVER ISLAND MONDAY WILL GIVE A BURST
OF STORM FORCE WINDS TO THE COASTAL WATERS...ENTRANCES...AND
NORTHERN INLAND WATERS. GALES WILL DEVELOP ELSEWHERE.

A SECOND STRONGER 975 MB LOW WILL DEVELOP IN THE OFFSHORE WATERS AND
MOVE INTO VANCOUVER ISLAND LATE MONDAY NIGHT OR TUESDAY. THIS LOW
WILL BE RAPIDLY DEEPENING...CONTAINS STRONG WINDS ALOFT...AND WILL
HAVE AN EXPANSIVE WIND FIELD. WIDESPREAD STORM OR HIGH END GALE
FORCE WIND CONDITIONS ARE EXPECTED WITH THIS SYSTEM.

COASTAL FLOODING...WHILE NOT CERTAIN...IS A POSSIBILITY WITH THE
HIGH TIDE THAT OCCURS MIDDAY TUE. LOW PRESSURE...PERSISTENT STRONG S
WIND ALONG THE COAST...AND HIGH WAVES OF 20 FT...WILL GIVE TIDAL
ANOMALIES OF UP TO 3 FT....AND THIS COULD CAUSE SOME FLOODING IF THE
STORM TIMING LINES UP WITH THE MIDDAY TUESDAY HIGH TIDE. A COASTAL
FLOOD WATCH HAS BEEN ISSUED FOR TUE ALONG THE CENTRAL
COAST.

ANOTHER VIGOROUS FRONT WILL MOVE THROUGH THE AREA WED NIGHT OR EARLY
THU. ALBRECHT

&&

.AVALANCHE...RELATIVELY LARGE AMOUNTS OF RECENT COLD..WEAK SNOW
LAYERS ARE GRADUALLY BEING EITHER LOADED OR WEAKENED BY INCREASINGLY
HEAVY ...DENSER SNOW OR RAIN WITH INCREASED AVALANCHE ACTIVITY THE
LIKELY OUTCOME. THIS WEATHER TREND OF WARMER...WET...AND WINDY
SHOULD CONTINUE RELATIVELY UNABATED OVER THE NEXT 24 HOURS IN THE
OLYMPICS AND NORTHERN WA CASCADES...THOUGH A BRIEF DECREASE IN
PRECIPITATION INTENSITY IS LIKELY IN THE SOUTH AND CENTRAL CASCADES
OVERNIGHT. AS A RESULT OF BOTH CURRENT AND ANTICIPATED WEATHER A
SIGNIFICANT INCREASE IN THE AVALANCHE DANGER IS UNDERWAY WITH
APPROPRIATE WARNINGS ISSUED FOR GENERALLY HIGH DANGER IN THE NORTH
CASCADES AND OLYMPICS AND MORE MODEST THOUGH STILL SIGNIFICANT
DANGER INCREASES ELSEWHERE. DESPITE THE BRIEF DECREASE IN THE SOUTH
AND CENTRAL CASCADES OVERNIGHT...FURTHER STRONG STORM RELATED
PRECIPITATION AND VERY STRONG WINDS SHOULD RETURN LATER MONDAY INTO
EARLY TUESDAY. EARLY SEASON BACK COUNTRY TRAVELERS SHOULD MINIMIZE
THEIR TIME IN AND EXPOSURE TO STEEPER AVALANCHE TERRAIN UNTIL THE
RECENT SNOWPACK BEGINS TO STABILIZE ...EITHER THROUGH SETTLEMENT OR
FURTHER AVALANCHES. SEE NWAC.US FOR DETAILS. MOORE

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNING CENTRAL AND NORTH WASHINGTON
     COAST...NORTH INTERIOR FROM LATE TONIGHT THROUGH MIDDAY TUESDAY.
    .WIND ADVISORY REMAINDER OF WESTERN WASHINGTON LATE TONIGHT
     THROUGH MONDAY AFTERNOON.
    .HIGH WIND WATCH REMAINDER OF WESTERN WASHINGTON MONDAY EVENING
     THROUGH MIDDAY TUESDAY.
    .FLOOD WATCH IN EFFECT FOR VARIOUS COUNTIES IN WESTERN
     WASHINGTON.
    .COASTAL FLOOD WATCH FOR THE CENTRAL WASHINGTON COAST TUESDAY.
PZ...STORM WARNING COAST AND WEST ENTRANCE.
    .GALE WARNING EAST ENTRANCE...ADMIRALTY INLET...NORTH INLAND
     WATERS.
    .SMALL CRAFT ADVISORY CENTRAL STRAIT AND PUGET SOUND/HOOD
     CANAL.
    .SMALL CRAFT ADVISORY GRAYS HARBOR FOR ROUGH TO SEVERE BAR
     CONDITIONS.

WWW.WEATHER.GOV/SEATTLE

FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION...PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATESTWEBAFD.HTML.