High Wind in Washington, November 23 to 24, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST WED NOV 23 2011

.SYNOPSIS...A FRONTAL SYSTEM WILL GRADUALLY WEAKEN AND SHIFT EAST OF
THE AREA THIS EVENING. ANOTHER STRONG FRONT WILL BRING MORE
RAIN...MOUNTAIN SNOW...AND WIND TO PARTS OF WESTERN WASHINGTON ON
THANKSGIVING DAY THROUGH FRIDAY MORNING. YET ANOTHER FRONT WILL
BRING ANOTHER ROUND OF RAIN AND WIND OVER THE WEEKEND. DRY WEATHER
IS POSSIBLE NEXT TUESDAY BEFORE ANOTHER FRONT ARRIVES.

&&

.SHORT TERM...IR SATELLITE IMAGERY SHOWS AND ELONGATED MOISTURE BAND
PRODUCING PRECIPITATION FROM WA SOUTH THROUGH OREGON AND CA. THE
MAIN SURFACE FRONT MOVED EAST OF THE CASCADES THIS MORNING BUT A
RESIDUAL BAND OF RAIN HAS LINGERED MAINLY E OF PUGET SOUND AND OVER
THE CASCADES WITH JUST SHOWERS ELSEWHERE IN WRN WA. THIS RAIN SHOULD
QUICKLY TAPER OFF THIS EVENING WITH JUST A FEW SHOWERS OVERNIGHT.
THE ONE AREA THAT RAIN WILL CONTINUE AT TIMES THROUGH TONIGHT WILL
BE WITHIN THE CONVERGENCE ZONE FROM SEATTLE NORTH THROUGH WRN
SNOHOMISH COUNTY. BOTH THE NAM-12 AND GFS HOLD ONTO THIS FEATURE
THROUGH THE NIGHT BEFORE DISSIPATING LATE.

SOUTHEAST GRADIENTS WILL INCREASE DRAMATICALLY EARLY FRIDAY MORNING
AS A 971MB SURFACE LOW TRACKS OFF THE CENTRAL B.C. COAST. THE WRFGFS
GIVES HIGH END GALES...ALMOST BORDERING ON STORM FORCE WINDS FOR
THE COASTAL WATERS AND N INTERIOR. THIS SYSTEM APPEARS TO BE JUST A
BIT WEAKER THAN THE PREVIOUS ONE SO I OPTED TO GO WITH A WIND
ADVISORY FOR THE COAST AND N INTERIOR FROM ADMIRALTY INLET NWD
INDICATING GUSTS TO 55 MPH...JUST SHY OF WARNING CRITERIA. THE
STRONGEST GUSTS WILL LIKELY OCCUR ALONG THE FRONT AS IT REACHES THE
COAST BY MIDDAY MOVES THROUGH THE N INTERIOR BY EARLY AFTERNOON.

COLDER AIR WILL FILTER INTO WRN WA TONIGHT WITH SNOW LEVELS FALLING
TO AROUND 2500 FEET BY THURSDAY MORNING. RAIN WILL REACH THE COAST
AND SPREAD INTO THE OLYMPICS BY DAY BREAK...THEN QUICKLY OVERSPREAD
THE REST OF WRN WA INCLUDING THE CASCADES BY AFTERNOON. SNOW LEVELS
MAY RISE SLIGHTLY IN THE AFTERNOON TO 3000 FEET BEFORE DROPPING BACK
DOWN IN THE EVENING. THIS MEANS PRECIPITATION WILL BE ALL SNOW FOR
MOST PASSES. INITIALLY...THE S/SW FACING SLOPES OF THE OLYMPICS AND
CASCADES INCLUDING SPOTS LIKE MT. BAKER AND PARADISE WILL PICK UP A
FEW INCHES OF SNOW BEFORE THE FAST MOVING FRONT PUSHES THROUGH BY
EVENING. SNOW WILL BECOME HEAVY AT TIMES IN THE CASCADES BEHIND THE
FRONT AND CONTINUE THROUGH THE NIGHT BEFORE EASING UP AND BECOMING
SHOWERY FRIDAY MORNING. STRONG WLY OROGRAPHIC FLOW SHOULD ENHANCE
SNOWFALL AMOUNTS ALONG THE W FACING SLOPES OF THE OLYMPICS AND IN
THE PASSES. 8 TO 14 INCHES OF SNOW ARE EXPECTED...THE HEAVIEST OF IT
FALLING LATE THURSDAY AFTERNOON AND NIGHT.

SHOWERS AND MOUNTAIN SNOW DECREASE FRIDAY MORNING WITH A DRY PERIOD
POSSIBLE FOR MUCH OF THE AREA LATER FRIDAY AND FRIDAY NIGHT. POPS
WERE REMOVED FOR MUCH OF THE FORECAST AREA WHILE WE ARE BETWEEN
SYSTEMS.

MODELS GENERALLY AGREE ON LIFTING A MOIST WARM FRONT ACROSS WRN WA
ON SATURDAY SPREADING RAIN ACROSS THE AREA. THERE IS SOME
UNCERTAINTY AS TO HOW MUCH RAIN WILL EVENTUALLY FALL WITH THIS
SYSTEM BUT IT DOES LOOK RATHER WET OVER THE WEEKEND. SEE THE LATEST
HYDRO SECTION FOR DETAILS.

.LONG TERM...IF THE GFS IS CORRECT...A ROUND OF HEAVY RAIN ON SUNDAY
WILL QUICKLY PUSH SE OF THE AREA ON SUNDAY NIGHT. SOME COLDER AIR
WILL FILTER IN FOR A CHANGE OVER TO SNOW SHOWERS IN THE CASCADES BUT
IT DOES NOT LOOK HEAVY OR PROLONGED AT THIS POINT. THE LATEST
GFS/ECMWF BOTH BUILD A RIDGE OVER THE PAC NW ON MONDAY INTO MONDAY
NIGHT FOR WHAT LOOKS LIKE DRY WEATHER. DECIDED TO REMOVE POPS GIVEN
THAT MODELS AGREE ON THIS. THE NEXT WEAK LOOKING FRONT HAS A TOUGH
TIME PUSHING INTO WRN WA ACCORDING TO THE GFS. HOWEVER...THE ECMWF
IS STRONGER AND DOES BRING A FAST MOVING BUT SHARP TROUGH THROUGH
THE AREA WITH PRECIP BY LATER TUESDAY AND WEDNESDAY. MOST NW FLOW
WITH A CHANCE OF RAIN CONTINUES THROUGH THE MIDDLE OF NEXT WEEK.
PERHAPS MORE SNOW IN THE MOUNTAINS IF THE ECMWF MODEL IS CORRECT.
THE GFS IS NOT AS WET OR COLD SO THERE IS A LOT OF UNCERTAINTY IN
THE FORECAST BY NEXT WEEK.  MERCER

&&

.HYDROLOGY...THE UPPER REACHES OF WESTERN WASHINGTON RIVERS HAVE
CRESTED NOW...AND THE CRESTS WILL BE MAKING THEIR WAY DOWNSTREAM
TONIGHT AND THURSDAY. THE EXCEPTION IS THE CHEHALIS RIVER...A
UNIQUELY SLOW MOVING RIVER IN WESTERN WASHINGTON...WHERE THE CREST
WILL MOVE THROUGH THE CENTRALIA AREA AND THURSTON COUNTY LATE
TONIGHT AND THURSDAY MORNING AND THEN DOWNSTREAM THROUGH GRAYS
HARBOR COUNTY THURSDAY AND THURSDAY NIGHT.

WESTERN WASHINGTON WILL EXPERIENCE RELATIVELY DRY WEATHER TONIGHT
AND THURSDAY MORNING. THE NEXT FRONTAL SYSTEM...WHICH WILL MOVE
THROUGH THE FORECAST AREA THURSDAY AFTERNOON THROUGH FRIDAY
MORNING...IS NOT EXPECTED TO BE HYDROLOGICALLY SIGNIFICANT. IN OTHER
WORDS IT WILL NOT RENEW FLOODING. PRECIPITATION AMOUNTS WILL RANGE
FROM 1 TO 2.5 INCHES OVER THE MOUNTAINS BUT THE SNOW LEVEL WILL BE
AROUND 2000 FT...SO IT WILL BE A SNOW PRODUCER RATHER THAN A FLOOD
PRODUCER.

FLOOD WARNINGS REMAIN IN EFFECT FOR SEVERAL WESTERN WASHINGTON
RIVERS. THEY ARE THE SKOKOMISH...NOOKSACK AT NORTH CEDARVILLE...
NORTH FORK STILLAGUAMISH...STILLAGUAMISH...PUYALLUP NEAR ORTING...
DESCHUTES...NEWAUKUM...AND CHEHALIS RIVER AT PORTER.

IN ADDITION THE FLOOD WATCH REMAINS IN EFFECT FOR WHATCOM...
SNOHOMISH...KING...LEWIS...AND THURSTON COUNTIES. THE FLOOD WATCH
COVERS THE POSSIBILITY OF MINOR FLOODING ON THE LOWER REACH OF THE
NOOKSACK...THE LOWER REACH OF THE SNOQUALMIE...AND THE REACH OF THE
CHEHALIS IN CENTRALIA AND GRAND MOUND AS THOSE CRESTS MOVE THROUGH.
THE LATEST HYDROLOGIC MODELS SHOW ALL THOSE SITES CRESTING BELOW BUT
WITHIN A FOOT OF FLOOD STAGE. IF THE RIVER CRESTS JUST A BIT HIGHER
THAN THE FORECAST...THEN THEY COULD REACH FLOOD STAGE.

WE HAVE ALLOWED THE FLOOD ADVISORY FOR URBAN AND SMALL STREAM
FLOODING THAT COVERED THE PUGET SOUND REGION AND SOUTHWEST INTERIOR
OF WASHINGTON TO EXPIRE AT 230 PM THIS AFTERNOON.

LOOKING FURTHER AHEAD...ANOTHER FRONTAL SYSTEM WILL MOVE THROUGH THE
AREA OVER THE WEEKEND. ITS WARM FRONT WILL BRING SIGNIFICANT
PRECIPITATION TO VANCOUVER ISLAND FRIDAY NIGHT THROUGH SATURDAY
NIGHT...BUT THE HEAVIEST RAIN WILL MISS OUR FORECAST AREA. THE
SYSTEM WILL WEAKEN AS IT MOVES EASTWARD ACROSS WESTERN WASHINGTON
SATURDAY NIGHT THROUGH SUNDAY NIGHT. WE WILL NEED TO PAY ATTENTION
TO THIS FEATURE OVER THE NEXT FEW DAYS...BUT AT THIS TIME IT APPEARS
THAT IT WILL NOT RENEW FLOODING EXCEPT PERHAPS ON THE SKOKOMISH
RIVER.

A FINAL NOTE ABOUT LANDSLIDES...THE USGS LANDSLIDE GUIDANCE
INDICATES THAT LANDSLIDES WILL BE POSSIBLE IF MODERATE TO HEAVY
RAIN OCCURS. SPECIAL WEATHER STATEMENTS COULD BE ISSUED OVER THE
NEXT FEW DAYS TO ADDRESS THAT THREAT.   MCDONNAL

&&

.AVIATION...WEAK ONSHORE FLOW THIS EVENING WILL DIMINISH AS A RIDGE
OF HIGH PRES SHIFTS E ACROSS THE AREA. THE AIR MASS IS MOIST AND
SOMEWHAT UNSTABLE THIS AFTERNOON...THE AIR MASS WILL STABILIZE
SOMEWHAT LATE TONIGHT AS THE RIDGE MOVES ACROSS THE AREA. MODERATE W
FLOW ALOFT WILL BECOME SW OVERNIGHT. MAINLY VFR CONDITIONS ARE
EXPECTED THIS EVENING...EXCEPT MVFR TO LOCALLY IFR CONDITIONS OVER
THE CENTRAL PUGET SOUND AREA WITH A CONVERGENCE ZONE. THE
CONVERGENCE ZONE WILL WEAKEN AS IT SHIFTS NORTH LATER IN THE EVENING.

A STRONG COLD FRONT OFFSHORE WILL MOVE TO THE WASHINGTON COAST BY
00Z FRI AND SHIFT RAPIDLY THROUGH THE INTERIOR 00Z-03Z FRI. EXPECT
MAINLY MVFR CONDITIONS IN CEILING AND RAIN AHEAD OF AND WITH THIS
FRONT. SW FLOW ALOFT WILL BECOME QUITE STRONG AHEAD OF THE FRONT
WITH WINDS AT 5000 FT INCREASING TO 60 KT AHEAD OF AND ALONG THE
FRONT. THIS STRONG FLOW WILL INTERACT WITH THE TERRAIN GIVING AREAS
OF SE WINDS AT THE SURFACE OF GREATER THAN 30 KNOTS.

KSEA...EXPECT LIGHT WINDS WITH THE CONVERGENCE ZONE NEAR OR JUST
NORTH OF THE TERMINAL THIS EVENING. WINDS WILL BECOME SE 4-6 KT
DURING THE EVENING AS THE CONVERGENCE ZONE SHIFTS NORTHWARD AND
WEAKENS. BKN010-015 AROUND THE CONVERGENCE ZONE SHOULD SCATTER OUT
WITH SCT030 BKN060 DOMINATING 03Z-06Z. THE LAYER AROUND 030 WILL
FILL IN OVERNIGHT THEN LOWER TO 020 AS -RA BEGINS IN THE MORNING.
ALBRECHT

&&

.MARINE...A WEAK RIDGE OF HIGH PRES WILL SHIFT EAST ACROSS THE AREA
TONIGHT.

A STRONG COLD FRONT ASSOCIATED WITH A DEEP 970-975 MB LOW MOVING
INTO THE EXTREME SE ALASKA PANHANDLE WILL SWEEP THROUGH THE WATERS
THURSDAY AFTERNOON AND EARLY EVENING. IT APPEARS THAT THE FRONT WILL
MOVE ONTO THE COASTLINE AROUND 4 PM THURSDAY AFTERNOON AND QUICKLY
THROUGH THE INLAND WATERS BY 7 PM. A STORM WARNING IS IN EFFECT FOR
THE WASHINGTON COAST WHILE GALE WARNINGS HAVE BEEN ISSUED FOR THE
OTHER WATERS FOR THU EXCEPT PUGET SOUND AND HOOD CANAL...WHERE A
SMALL CRAFT ADVISORY HAS BEEN ISSUED.

STRONG POST FRONTAL ONSHORE FLOW WILL FOLLOW THE FRONT WITH GALE
FORCE WESTERLIES IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
THE ONSHORE FLOW WILL RELAX LATE THURSDAY NIGHT INTO EARLY FRI.

A STRONG WARM FRONT WITH AREAS OF GALE FORCE WINDS WILL LIFT NORTH
ACROSS THE COASTAL WATERS FRIDAY NIGHT AND INTO EARLY SATURDAY. THIS
FRONT WILL BRUSH THE NORTHERN WATERS OF THE INTERIOR OF WESTERN
WASHINGTON AS WELL. A COLD FRONT WILL FOLLOW ON SUNDAY AND MAY
PRODUCED MORE GALES...ESPECIALLY IN THE COASTAL WATERS.

SEAS WILL BUILD TO OVER 20 FEET IN THE COASTAL WATERS THURSDAY AND
CONTINUE IN SWELL THURSDAY NIGHT. ANOTHER PERIOD OF SEAS NEARING 20
FT IS LIKELY SATURDAY INTO SUNDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY NORTH AND CENTRAL COAST AND NORTH INTERIOR
     ON THURSDAY.
    .WINTER STORM WARNING NORTH AND CENTRAL CASCADES THURSDAY
     THROUGH FRIDAY MORNING.
    .WINTER WEATHER ADVISORY FOR THE OLYMPICS THURSDAY THROUGH
     THURSDAY NIGHT.
    .FLOOD WATCHES AND WARNINGS REMAIN IN EFFECT FOR PARTS OF
     WESTERN WASHINGTON.
PZ...STORM WARNING COASTAL WATERS LATE TONIGHT THROUGH
     THURSDAY.
    .GALE WARNING STRAIT...NORTHERN INLAND WATERS AND ADMIRALTY
     INLET THURSDAY.
    .SMALL CRAFT ADVISORY COASTAL WATERS AND WEST ENTRANCE TO
     THE STRAIT OF JUAN DE FUCA FOR HAZARDOUS SEAS THROUGH TONIGHT.
    .SMALL CRAFT ADVISORY CENTRAL AND EAST ENTRANCE STRAIT OF JUAN
     DE FUCA THIS EVENING.
    .SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR SEVERE BAR CONDITIONS.

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

WWW.WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
345 PM PST WED NOV 23 2011

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

0345 PM     HEAVY RAIN       5 ESE MONTESANO         46.98N 123.50W
11/23/2011  M4.82 INCH       GRAYS HARBOR       WA   TRAINED SPOTTER

            STORM TOTAL.

&&

GRUB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
416 PM PST WED NOV 23 2011

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

0415 PM     HEAVY RAIN       5 SSE BREMERTON         47.48N 122.66W
11/23/2011  M2.85 INCH       KITSAP             WA   TRAINED SPOTTER

            24 HOUR RAINFALL AS OF 4 PM.

&&

GRUB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
624 PM PST WED NOV 23 2011

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

0623 AM     HEAVY RAIN       4 NE BREMERTON          47.59N 122.63W
11/23/2011  M5.80 INCH       KITSAP             WA   TRAINED SPOTTER

            48 HOUR RAINFALL AS OF 6 AM.

&&

GRUB