High Wind in Washington, January 15, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
945 PM PST THU JAN 14 2010...UPDATED

.SYNOPSIS...A STRONG FRONT WILL REMAIN JUST OFFSHORE THROUGH TONIGHT
THEN SLIDE SOUTHEAST ACROSS THE AREA LATER FRIDAY AS IT WEAKENS.
ANOTHER FRONT IS EXPECTED TO REACH THE COAST SUNDAY WITH A DEEP LOW
PRESSURE SYSTEM PASSING BY SUNDAY NIGHT INTO MONDAY.  BEYOND THAT A
SERIES OF SYSTEMS WILL AFFECT THE AREA TUESDAY THROUGH THE REMAINDER
OF THE WEEK.

&&

.SHORT TERM...RADAR AND SATELLITE IMAGERY SHOW THE HEAVIEST PRECIP
IS STARTING TO LIFT SLIGHTLY NWD...NOW MAINLY IMPACTING THE OLYMPIC
PENINSULA. BOTH THE NAM/GFS HAVE HINTED AT THIS AS A LOW DEEPENS
ALONG THE BAROCLINIC BAND OFF THE OREGON COAST THIS EVENING. WHILE
RAIN WILL CONTINUE ACROSS THE ENTIRE AREA TONIGHT...THE N/CENTRAL
CASCADES SHOULD SEE A LULL IN PRECIP RATES. EVEN THE OLYMPICS MAY
SEE RAINFALL RATES EASE A BIT OVERNIGHT BUT NOT ENOUGH TO HEAD OFF
FLOODING WITH THE SKOKOMISH EXPECTED TO REACH FLOOD STAGE BY
MIDNIGHT. AS THIS WAVE TRAVELS NE OFF THE WA COAST FRIDAY
MORNING...HEAVIER RAINFALL WILL ONCE AGAIN PICK UP ACROSS THE
OLYMPICS WITH IMPRESSIVE RAINFALL AMOUNTS EXPECTED DUE TO STRONG
SW FLOW ALOFT. THE FRONTAL BAND WILL SHIFT SLIGHTLY SOUTH LATER ON
FRIDAY ALLOWING THE HEAVIER RAIN TO ALSO DEVELOP ACROSS THE
N/CENTRAL CASCADES. THEREFORE...THE FLOOD WATCH WAS EXPANDED EARLIER
TO COVER KING...PIERCE...LEWIS...AND THURSTON COUNTIES.

UPDATED...A HIGH WIND WARNING REMAINS IN EFFECT FOR THE OLYMPIC
MOUNTAINS FOR STRONG WINDS ABOVE AROUND 1500 FEET. HURRICANE RIDGE
ALREADY OVER 40 MPH SUSTAINED WITH GUSTS INTO THE MID 60S. IT WILL
ONLY GET STRONGER OVERNIGHT. WINDS HAVE QUICKLY PICKED UP ACROSS THE
N INTERIOR WITH WHIDBEY ISLAND REPORTING SUSTAINED WINDS OF 36 MPH
WITH HIGHER GUSTS. DECIDED TO GO AHEAD AND ISSUE A WIND ADVISORY FOR
THE WHIDBEY ISLAND AREA NORTHWARD THROUGH MIDDAY FRIDAY.

MODELS WEAKEN THE FRONTAL BAND CONSIDERABLY AS IT SHIFTS INTO SRN WA
BY SATURDAY MORNING. PRECIP SHOULD BEGIN TO WIND DOWN OR END OVER
MANY AREAS BUT RESIDUAL FLOODING IS STILL LIKELY IN SOME RIVER
BASINS. THE NEXT SYSTEM MOVES THROUGH SATURDAY NIGHT OR SUNDAY WITH
MORE WIND AND RAIN. THIS SYSTEM WILL BE MORE PROGRESSIVE THAN THE
CURRENT ONE WHICH WILL HELP LIMIT PRECIP AMOUNTS. MERCER

.LONG TERM...PREVIOUS DISCUSSION FOLLOWS...THIS TIMEFRAME WILL BE AN
ACTIVE ONE WEATHER WISE.  THE UPPER RIDGE WILL SHIFT WELL EAST OF
THE REGION ALLOWING THE PACIFIC NW TO BE UNDER THE INFLUENCE OF THE
DEEP TROUGH OFFSHORE.  THE RESULT WILL BE A SERIES OF STORM SYSTEMS
THE WILL RIDE UP THE EAST SIDE OF THIS TROUGH AND ACROSS OUR AREA
FROM SUNDAY ONWARD...LIKELY THROUGH ALL OF NEXT WEEK.  IT WILL BE A
WET PERIOD PROBABLY BEST DESCRIBED AS...PERIODS OF RAIN WITH
SOMEWHAT ABOVE NORMAL TEMPERATURES.  SPECIFICS ARE QUITE LACKING AT
THIS POINT BUT ONE OF THESE STORM SYSTEMS COULD BE GOOD FOR STRONGER
WINDS ACROSS PARTS OF WESTERN WASHINGTON SUNDAY INTO TUE.  IT
DEPENDS ON JUST HOW CLOSE TO THE COAST THE STORMS PASS BY SO THIS
WILL NEED TO BE WATCHED.  THERE WILL BE ENOUGH RAIN THROUGH NEXT
WEEK THAT BESIDE THE NORMAL LOCAL HIGH WATER ISSUES THE THREAT OF
LOCAL LANDSLIDES WILL REMAIN WITH US.  CERNIGLIA

&&

.HYDROLOGY...PRECIP RATES HAVE EASED OVER THE CASCADES OF WRN WA
THIS EVENING AS THE FRONTAL BAND LIFTS SLIGHTLY NWD. THE OLYMPICS
CONTINUE TO SEE HEAVY RAINFALL RATES...UP TO A HALF INCH PER HOUR
ACROSS S/SW FACING SLOPES. SEVERAL SITES HAVE ALREADY MEASURED
NEARLY 3 INCHES IN THE PAST 12 HOURS WITH BLACK KNOB PICKING UP
ALMOST 2 INCHES IN JUST THE PAST 6 HOURS. THESE RATES COULD EASE A
BIT OVERNIGHT IF THE FLOW LIFTS SLIGHTLY NWD BUT VERY HEAVY RAIN IS
EXPECTED AGAIN EARLY FRIDAY MORNING AS THE MAIN FRONTAL BAND SAGS
BACK OVER THE AREA. HEAVY RAIN WILL ALSO SPREAD INTO THE N CASCADES
DURING THE MORNING AND EVENTUALLY INTO THE CENTRAL CASCADES BY
AFTERNOON. THE 00Z MM5 24 HOUR RAINFALL AMOUNTS ARE SHOWING ABOUT 2
TO 4 MORE INCHES FOR THE OLYMPICS. THE N/CENTRAL CASCADES WILL SEE
LESS...MAYBE 2 TO 4 INCHES. AMOUNTS ACROSS THE CENTRAL CASCADES ARE
IN MOST QUESTION AND HIGHLY DEPENDENT ON JUST HOW QUICKLY THE FRONT
PUSHES SWD FRIDAY NIGHT. OVERALL...THE MODELS SEEM TO SHOW LESS
THREAT OF FLOODING OVER THE CASCADES WITH THE HIGHEST RISK TO THE
OLYMPIC RIVER BASINS. WILL KEEP WITH FLOOD WATCH GOING AS THE
PROGRESSION OF THE MOISTURE PLUME REMAINS IN QUESTION.

ALTHOUGH THIS SYSTEM CONTAINS A GOOD DEAL OF MOISTURE...THE FLOW
DIRECTION IS NOT CONDUCIVE FOR HEAVY RAIN IN THE GREEN RIVER BASIN.
THEREFORE FLOODING IS NOT EXPECTED ON THE GREEN RIVER.

PREVIOUS EXTENDED DISCUSSION...BEYOND SATURDAY...THE NEXT WEEK WILL
FEATURE NUMEROUS FAST-MOVING WEATHER SYSTEMS THAT WILL BRING
MODERATE RAINS...BUT THE DURATION OF RAINFALL AND BREAKS BETWEEN
WEATHER SYSTEMS SHOULD PRECLUDE LARGE-SCALE FLOODING
CONCERNS...ALTHOUGH SELECT...EASY TO FLOOD RIVERS WILL BE UNDER
THREAT OF RENEWED FLOODING THROUGHOUT NEXT WEEK.

ALL THIS RAIN ALSO BRINGS ABOUT A CONTINUED THREAT FOR SCATTERED
LANDSLIDES.  THE USGS LANDSLIDE INDEX INDICATES THAT THE GROUND IS
SUFFICIENTLY WET...BUT THAT RAINFALL 12-24 HR RAINFALL AMOUNTS ARE
ACROSS THE ENTIRE AREA DON'T EXCEED CRITERIA TO TRIGGER MORE
EXTENSIVE LANDSLIDE PROBLEMS.  GIVEN THE CONDITIONS AND THE FORECAST
OVER THE NEXT WEEK...WIDELY SCATTERED LANDSLIDES ARE A POSSIBILITY
THROUGH NEXT WEEK.

FLOODING IS NOT EXPECTED ON THE GREEN RIVER FOR THE NEXT 10 DAYS.

CERNIGLIA/MERCER

&&

.AVIATION...A TRAIN OF SYSTEMS EXTENDS ALONG A BAROCLINIC BOUNDARY
FROM THE QUEEN CHARLOTTE SOUND SOUTH TO 48N/130W THEN SW TO THE
TROPICAL EAST PACIFIC EAST OF HAWAII. ONE WARM FRONTAL BAND IS
MOVING THROUGH THROUGH W WA THIS EVENING. THE DIFFICULT TO FIND
BOUNDARY APPEARS TO SIT FROM NEAR KSMP WNW TO THE NORTH WASHINGTON
COASTAL WATERS WEST OF KUIL. RAIN APPEARS TO BE COMING TO AN END
SOUTH OF THIS BOUNDARY. CIGS ARE MVFR ALONG THE COAST AND NEAR THE
OLYMPICS WHILE THEY ARE MAINLY VFR NEAR THE CASCADES WITH THE SELY
PRES GRADIENTS IN PLACE.

CONDITIONS TO THE NORTH OF THE FRONT WILL IMPROVE OVERNIGHT AS THE
FRONT PUSHES N INTO CANADA. TO THE SOUTH OF THE FRONT EXPECT LITTLE
CHANGE UNTIL 14Z-1Z TIME FRAME WHEN RAIN WITH THE OFFSHORE FRONTAL
BAND MOVES INTO THE AREA. WHILE THE FRONTAL SYSTEM WILL BE WEAKENING
AS IT MOVES INLAND...PRE-FRONTAL WINDS ALOFT ARE QUITE STRONG WITH
SW70 KT AT 050 AND ABUNDANT TROPICALLY CHARGED MOISTURE HAS BEEN
ADVECTED RAPIDLY NORTHWARD ALONG THE FRONT. SO EXPECT CIGS AND VIS
TO FALL TO IFR FRI MORNING AND THERE THROUGH MUCH OF FRI NIGHT AS
THE FRONT WEAKENS AND CRAWLS ACROSS SE ACROSS W WA.

KSEA...EXPECT P6SM OVC035-045 WITH OCCASIONAL -RA THROUGH ABOUT 14Z.
EXPECT PRECIPITATION INTENSITY TO INCREASE FRI MORNING A THE
OFFSHORE FRONTAL BAND APPROACHES. WITH TROPICAL MOISTURE AHEAD OF
THE INCOMING FRONT EXPECT 1-3SM RA OVC008-012 MUCH OF THE DAY FRI
WITH S WIND 08-12KT. WIND AT 020 EXPECTED 21050KT RESULTING IN LOW
LEVEL WIND SHEAR STARTING AROUND 12Z TONIGHT AND CONTINUING UNTIL
THE FRONT COLLAPSES OVERHEAD JUST BEFORE 00Z SAT. CIGS AND VIS WILL
LIKELY REMAIN IFR THROUGH EARLY SAT MORNING. ALBRECHT

&&

.MARINE...A TRAIN OF SYSTEMS EXTENDS ALONG A FRONTAL BAND FROM THE
QUEEN CHARLOTTE SOUND SOUTH TO 48N/130W THEN SW TO THE TROPICAL EAST
PACIFIC EAST OF HAWAII. ONE WARM FRONTAL BAND IS MOVING THROUGH
THROUGH W WA THIS EVENING. A FRONTAL WAVE APPEARS TO SIT NEAR
42N/135W PER SATELLITE IMAGERY.

GALE FORCE S TO SE WINDS IN THE NORTH INTERIOR AND EASTERN STRAIT OF
JUAN DE FUCA AREAS AHEAD OF THE WARM FRONT WILL POSSIBLY COME DOWN A
BIT FOR A COUPLE HOURS LATE TONIGHT...BUT WILL INCREASE AGAIN DURING
THE EARLY MORNING HOURS AS THE OFFSHORE FRONT APPROACHES...AND VERY
STRONG SW FLOW ALOFT INTERACTS WITH THE OLYMPICS. SMALL CRAFT
ADVISORY SOUTH WINDS WILL DEVELOP IN THE PUGET SOUND AREA AS ENERGY
MIXES DOWN AHEAD OF THE FRONT.

WINDS WILL EASE IN THE AFTERNOON AS THE FRONT MOVES INLAND AND
WEAKENS. WEAK HIGH PRES BUILDS SATURDAY FOR LIGHT OFFSHORE
FLOW...THEN SEVERAL STRONG SYSTEMS WILL AFFECT THE REGION SUN-WED.

MINOR TIDAL OVERFLOW IS A CONCERN FOR SEATTLE FRI NIGHT AND AGAIN
SAT NIGHT DURING THE HIGH TIDES. HIGH ASTRONOMICAL TIDES COMBINED
WITH LOW ATMOSPHERIC PRESSURE IS EXPECTED TO GIVE TIDAL ANOMALIES
AROUND 13.5 FT FRI NIGHT AND 14.1 FT SAT NIGHT. WILL LIKELY ISSUE A
COASTAL FLOOD ADVISORY FOR MINOR TIDAL OVERFLOW WITH THE EARLY
MORNING PACKAGE. ALBRECHT

&&

WA...VARIOUS FLOOD WATCHES AND WARNINGS ARE IN EFFECT FOR WESTERN
     WASHINGTON.
    .HIGH WIND WARNING IS IN EFFECT FOR THE OLYMPICS THROUGH FRIDAY.
    .WIND ADVISORY FOR THE NORTH INTERIOR THROUGH MIDDAY FRIDAY.

PZ...GALE WARNING COASTAL WATERS...ENTRANCES TO THE
     STRAIT...NORTHERN INLAND WATERS.
    .SMALL CRAFT ADVISORY CENTRAL STRAIT...ADMIRALTY INLET...AND
     PUGET SOUND/HOOD CANAL.
    .SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR CONDITIONS.

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