River Flood Warning 52, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
342 PM PST MON NOV 16 2009

.SYNOPSIS...ANOTHER VIGOROUS SURFACE LOW WILL TRACK NORTHEAST INTO
VANCOUVER ISLAND TONIGHT WITH WINDS INCREASING ACROSS WESTERN
WASHINGTON. HIGHEST WINDS WILL ONCE AGAIN OCCUR ALONG THE COAST AND
NORTH INTERIOR. WINDS WILL EASE TUESDAY AFTERNOON AS THIS SYSTEM
MOVES INLAND AND WEAKENS. MEANWHILE HEAVY RAIN WILL CONTINUE ACROSS
THE REGION WITH RIVER FLOODING OCCURING OR POSSIBLE ACROSS THE
OLYMPICS...WILLAPA HILLS AND NORTH CASCADES. HEAVY RAIN WILL
DECREASE TUESDAY MORNING AS THE FRONTAL BAND SHIFTS SOUTHEAST OF THE
AREA. ACTIVE WEATHER WILL CONTINUE THROUGH MUCH OF THE WEEK AHEAD.

&&

.SHORT TERM...AN ACTIVE PERIOD OF WEATHER WILL CONTINUE ACROSS
WESTERN WA THROUGH THE SHORT TERM PERIOD. A SERIES OF VIGOROUS
SYSTEMS SWEEPING THROUGH THE REGION RESULTING IN VARIOUS HAZARDOUS
WEATHER HEADLINES TONIGHT AND TUE FROM STRONG WIND AND RIVER
FLOODING...TO HIGH SURF AND COASTAL FLOOD ADVISORIES.

WE HAVE REACHED OUR RELATIVE LULL IN THE WINDS RIGHT NOW WITH FAIRLY
LIGHT WINDS ACROSS MOST AREAS. WHIDBEY NAVEL EVEN WENT FROM SOUTH 20
GUST 34 KT AT 21Z DOWN TO JUST SE 3 KT AN HOUR LATER. AND PRES
GRADIENTS HAVE DROPPED SEVERAL MB FROM KOLM TO KBLI. IT WAS UP TO
6.5 THIS MORNING AND NOW DOWN TO 0.3. THIS BREAK WILL BE BRIEF AS
WINDS ARE EXPECTED TO RAMP BACK UP AS OUR NEXT LOW SWINGS BY
TONIGHT. ALTHOUGH THE SURFACE LOW IS FORECAST TO BE WEAKER...979 MB
AS IT MOVES NE INTO VANCOUVER ISLAND AT 12Z...IT STILL MAY PRODUCE A
PERIOD OF STRONG WINDS ONCE AGAIN ALONG THE COAST AND NORTH
INTERIOR. WILL KEEP WINDS AT LOW END WARNING CRITERIA WITH SOUTH
WINDS 35 TO 45 MPH AND GUST UP TO 60 MPH. ELSEWHERE...WINDS AGAIN
WILL BE IN THE ADVISORY RANGE OF 25 TO 35 WITH GUSTS TO 50 MPH. THE
STRAIT IS THE ONE AREA WHERE WINDS WILL BE RELATIVELY LIGHT. BY 20Z
THE LOW WILL FILL AS IT MOVES FARTHER INLAND INTO CENTRAL B.C. WITH
WINDS EASING ACROSS WESTERN WA.

THE OTHER CONCERN TONIGHT AND TUE IS HEAVY PRECIP WHICH IS OUTLINED
IN THE HYDROLOGY SECTION BELOW. WILL NEED TO WATCH LOWLAND ZONES
TONIGHT IF HEAVY RAIN CONTINUES OVER A PROLONGED PERIOD. CLOGGED UP
DRAINS WITH LEAVES MAY RESULT IN MINOR URBAN STREET FLOODING.

COASTAL WORRIES WITH SURF ARE ALSO DISCUSSED BELOW IN THE MARINE
SECTION.

THE BAROCLINIC BAND WILL SHIFT SE OF THE REGION TUE MORNING WITH
COOLER AIR MOVING IN BEHIND IT. SNOW LEVELS WILL LOWER BACK DOWN TO
AROUND 3000 FT IN THE AFTERNOON. THE THREAT FOR SHOWERS CONTINUES
INTO WED AS A SHORT WAVE UPPER LEVEL TROUGH PASSES THROUGH. ONCE
AGAIN WILL NEED TO WATCH FOR SNOW IN THE PASSES ALTHOUGH SNOW
AMOUNTS AT THIS TIME APPEAR BELOW WINTER WEATHER ADVISORY CRITERIA.
33

.LONG TERM...ANOTHER WARM FRONT WILL IMPACT W WA WED NIGHT INTO THU
WITH FREEZING LEVELS ONCE AGAIN RISING UP TO AROUND 5000 FT IN THE
OLYMPICS. THIS COULD BRING ANOTHER ROUND OF HEAVY RAIN FOR THE
PENINSULA AND POSSIBLY THE NORTH CASCADES AS WELL. MODELS DRIVE THE
HEAVY PRECIP SOUTH INTO ORE AND CA THU NIGHT INTO FRIDAY AS A DEEP
UPPER LOW DEVELOPS AND DIGS OFFSHORE. UNTIL THEN WILL NEED TO
MONITOR THE EVOLUTION OF THIS SYSTEM CLOSELY. EVENTUALLY MODELS
SHIFT THE DEEP UPPER LEVEL TROUGH INLAND WITH SNOW LEVELS ONCE AGAIN
LOWERING DOWN TO 2000 FT OR BELOW.

MAY SEE A BRIEF BREAK IN THE WEATHER SAT NIGHT...THEN ANOTHER SHORT
WAVE TROUGH SLIDES THROUGH ON SUN. 33

&&

.HYDROLOGY....SO FAR THE CURRENT FLOOD EVENT IS LIMITED TO THE
OLYMPIC PENINSULA. THREE RAIN GAUGES IN THE SOUTHERN OLYMPICS HAVE
ALL RECEIVED 6-8 INCHES OF RAIN. THREE RIVERS ARE UNDER A FLOOD
WARNING...THE SKOKOMISH...THE SATSOP...AND THE BOGACHIEL. THE
SKOKOMISH IS AT MAJOR FLOOD STAGE AND SEEMS DESTINED TO STAY THERE
AWHILE. THE ELWHA AND DUNGENESS RIVERS HAVE BEEN RISING STEADILY BUT
FLOODING IS NOT YET A SURE THING ON THOSE RIVERS. AN AREAL FLOOD
WARNING COVERS ALL SMALLER STREAMS AND RIVERS ON THE OLYMPIC
PENINSULA THROUGH TUESDAY EVENING.

THE CHEHALIS HAS BECOME A CONCERN. HEAVY RAIN IN THE WILLAPA HILLS
THIS MORNING WILL CONTINUE INTO THE EVENING. THIS IS DRIVING THE
CHEHALIS HEADWATERS UP AND MINOR FLOODING FOR THE CHEHALIS AT DOTY
IS PROBABLY COMING TONIGHT. ON THE OTHER HAND...THE NEWAUKUM
RIVER...A SIGNIFICANT CONTRIBUTER TO THE CHEHALIS DOWNSTREAM...HAS
BARELY BUDGED. THIS RIVER FLOWS OUT OF THE CENTRAL CASCADES WHERE
RAINFALL HAS BEEN MINIMAL. RIVER MODELS CALL FOR FLOODING ALL THE
WAY DOWN THE CHEHALIS...BUT THIS IS QUESTIONABLE UNLESS THE NEWAUKUM
GETS GOING OR THE UPSTREAM CHEHALIS RISES MORE THAN FORECAST. WILL
KEEP THE WATCH GOING ON MOST OF THE CHEHALIS AND ISSUE A FLOOD
WARNING FOR THE REACH AROUND DOTY.

IN THE NORTH CASCADES RIVERS ARE RISING. MODELS NOW PREDICT MINOR
FLOODING ON THE NOOKSACK AND SKAGIT...AND THE STILLAGUAMISH IS
RUNNING AHEAD OF MODELS. WILL KEEP WATCHING THESE RIVERS FOR NOW.

RAINFALL SOUTH OF SNOHOMISH COUNTY IN THE CASCADES HAS BEEN MUCH
LESS THAN IN THE NORTH CASCADES AND OLYMPICS. NO FLOODING IS
FORECAST ON THESE RIVERS...INCLUDING THE GREEN RIVER.

HYDROLOGICALLY SIGNIFICANT RAINFALL WILL END ON TUESDAY
MORNING...AND RIVERS WILL RECEDE ON WEDNESDAY. UNFORTUNATELY ANOTHER
SYSTEM ARRIVES WEDNESDAY NIGHT AND THIS LOOKS WET AS WELL. BOTH THE
GFS AND EURO BRING A 24-36 HOUR EVENT...AGAIN AIMED MOSTLY AT THE
OLYMPICS AND NORTH CASCADES. MANY RIVERS WILL NOT HAVE RECEDED MUCH
BELOW FLOOD STAGE BY THE TIME THE STORM HITS...SO FURTHER FLOODING
IS LIKELY.

MORE WEATHER SYSTEMS ARE DUE ABOUT SUNDAY AND ABOUT TUESDAY OF NEXT
WEEK. THESE ARE MORE PROGRESSIVE AND RAINFALL AMOUNTS MAY NOT BE
HEAVY. BURKE

&&

.AVIATION...STRONG SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON WITH
A FRONTAL BAND EXTENDING SOUTHWEST FROM SOUTHWEST BRITISH COLUMBIA
ACROSS THE WASHINGTON OFFSHORE WATERS. A DEVELOPING SURFACE LOW WILL
MOVE INTO THE OFFSHORE WATERS LATE TODAY...TRAVEL NORTHEAST ALONG
THE FRONTAL BAND AND CROSS VANCOUVER ISLAND LATE TONIGHT. THE
TRAILING OCCLUDED FRONT WILL MOVE THROUGH WESTERN WASHINGTON TUESDAY
MORNING.

STRONG LOW LEVEL WINDS WILL CONTINUE THROUGH TONIGHT. THE AREA
APPEARS TO BE IN A LULL BETWEEN SYSTEMS THIS AFTERNOON...BUT EXPECT
THE WINDS TO INCREASE AGAIN THIS EVENING AS THE NEXT LOW APPROACHES.
EXPECT THE STRONG SOUTHERLY LOW LEVEL WINDS TO INCREASE BACK UP TO
50-60 KT LATER THIS EVENING. LOW LEVEL WINDS ARE STRONG ENOUGH TO
KEEP THE MENTION OF LOW LEVEL WIND SHEAR IN MOST OF THE TAFS.
CONTINUING RAIN WILL LOWER CIGS BACK TO MAINLY MVFR THIS EVENING.
COULD SEE SPOTTY IFR CIGS.

KSEA...CIGS JUST DROPPED DOWN TO BKN008...BUT WITH MOST OF THE AREA
STILL RUNNING WITH HIGHER CIGS WILL JUST RUN A SHORT TEMPO GROUP TO
COVER THIS. EXPECT CIGS OVERALL TO LOWER A BIT MORE TO PRETTY
CONSTANT CIGS BELOW OVC020 FOR MUCH OF THE NIGHT. EXPECT STRONG S
FLOW ALOFT TO CONTINUE WITH S 35-50 KT BETWEEN KSEA AND
KOLM...RISING TO NEAR 60 KT 03Z-08Z. WILL KEEP THE MENTION OF LOW
LEVEL WIND SHEAR IN THE TAF. KAM

&&

.MARINE...A VIGOROUS FRONTAL SYSTEM WILL CONTINUE TO AFFECT THE
FORECAST AREA THROUGH TUESDAY. A FRONTAL BAND EXTENDS SOUTHWEST FROM
SOUTHWEST BRITISH COLUMBIA ACROSS THE OFFSHORE WATERS. MODELS AGREE
ON BRINGING A 980 MB LOW ACROSS NORTH OR CENTRAL VANCOUVER ISLAND
AROUND 12Z TUESDAY. IN ADDITION...THE NAM AND WRF/GFS INDICATE
A WEAKER LOW MOVING NE UP THE COLD FRONT AND ACROSS THE N COASTAL
WATERS AROUND MIDNIGHT. EXPECT ANOTHER ROUND OF LOW END STORM FORCE
WINDS COAST AND WEST ENTRANCE /TATOOSH ISLAND/ TONIGHT WITH THE
SECONDARY LOW...ALONG WITH GALE FORCE S WINDS OVER THE INLAND WATERS
AREA. AN AREA OF TIGHT PRESSURE GRADIENTS ON THE S SIDE OF THE MAIN
LOW MAY GIVE ANOTHER BURST OF SW WIND ACROSS THE WATERS TUESDAY
MORNING. THIS WOULD PROBABLY ONLY AFFECT THE N PART OF THE COASTAL
WATERS AND AGAIN THE W ENTRANCE...AND MAY END UP BEING JUST A GALE
IF THE LOW MOVES TOO FAR NORTH. WILL KEEP GALES UP FOR THE INTERIOR
FOR THIS FEATURE...ADDING A SW GALE FOR THE CENTRAL STRAIT. FRONTAL
SYSTEM PRONGED TO REACH THE AREA WEDNESDAY NIGHT AND THURSDAY HAS
SIMILARITIES TO THIS SYSTEM...BUT WILL DEAL WITH THAT ONE ONCE THIS
EPISODE HAS PASSED.

HAVE GONE WITH A COASTAL FLOOD ADVISORY/MINOR TIDAL OVER FLOW FOR
THE COAST. RAN THE HIGH SURF...WHICH IS AT THE LOW END NEAR 20
FEET...FROM LATER THIS EVENING THROUGH TUESDAY EVENING...THOUGH THE
PERIOD MAY END UP BEING SHORTER. ABERDEEN HIGH TIDE IS AT 1245 PM
TUESDAY. PRESSURES HAVE RISEN ENOUGH AND THE SWELL IS PROBABLY LOW
ENOUGH TO KEEP THE AREA BELOW COASTAL FLOOD WARNING CRITERIA. LOCAL
STORM SURGE ALGORITHM POPPED OUT 13.7 FEET FOR ABERDEEN COMPARED TO
THE 13.5 MINOR TIDAL OVERFLOW FOOT THRESHOLD. THOUGH THIS MODEL
OFTEN RUNS HIGH...WILL BE CONSERVATIVE AND ISSUE THE ADVISORY. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WARNING COAST AND NORTH INTERIOR THROUGH NOON TUESDAY.
    .WIND ADVISORY CENTRAL AND SOUTH INTERIOR THROUGH NOON TUESDAY.
    .FLOOD WATCHES AND WARNINGS ARE IN EFFECT FOR VARIOUS COUNTIES.
    .HIGH SURF ADVISORY IN EFFECT FOR THE NORTH AND CENTRAL COAST.
    .COASTAL FLOOD ADVISORY IN EFFECT FOR THE CENTRAL COAST.

PZ...STORM WARNING FOR THE COAST AND WEST ENTRANCE.
    .GALE WARNING EAST ENTRANCE...ADMIRALTY INLET...NORTH INLAND
     WATERS.
    .GALE WARNING PUGET SOUND FROM 10 PM TO 4 AM.
    .SMALL CRAFT ADVISORY PUGET SOUND UNTIL 10 PM.
    .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.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
205 PM PST MON NOV 16 2009

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

0700 AM     HEAVY RAIN       2 E SAPPHO              48.07N 124.24W
11/16/2009  M3.70 INCH       CLALLAM            WA   TRAINED SPOTTER

            24 HOUR AMOUNT

1200 PM     NON-TSTM WND GST 2 WNW ANACORTES         48.50N 122.66W
11/16/2009  M52.00 MPH       SKAGIT             WA   TRAINED SPOTTER

            WINDS HAVE BEEN SUSTAINED OUT OF THE SOUTH AROUND 25 MPH
            WITH GUSTS UP TO 52 MPH SINCE 9AM.

1200 PM     HEAVY RAIN       1 ENE ELWHA             48.06N 123.57W
11/16/2009  M2.16 INCH       CLALLAM            WA   TRAINED SPOTTER

            24 HOUR TOTAL.

&&

DDAMICO