Damaging Winds in Washington, December 14, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
945 PM PST MON DEC 13 2010

.SYNOPSIS...A COLD FRONT WILL MOVE THROUGH WESTERN WASHINGTON EARLY
TUESDAY MORNING. A MUCH COOLER AIR MASS WILL BE OVER THE REGION IN
THE WAKE OF THE COLD FRONT TUESDAY. DISTURBANCES WILL KEEP THE
WEATHER COOL AND SHOWERY INTO THE WEEKEND.

&&

.SHORT TERM...WSR-88D SHOWS PLENTY OF SHOWERS OUT AHEAD OF THE COLD
FRONT OFFSHORE OVER THE AREA THIS EVENING. ISSUED A URBAN AND SMALL
STREAM FLOOD ADVISORY EARLIER THIS EVENING WITH THE HEAVY BAND OF
SHOWERS THAT MOVED THROUGH THE AREA WITH THE SOILS ALREADY
SATURATED. THIS ADVISORY HAS EXPIRED. COLD FRONT OFFSHORE AT 05Z
JUST EAST OF 128W. TIMING OF THE FRONT ON THE 00Z MODELS SIMILAR TO
PREVIOUS RUNS WITH THE FRONT REACHING THE COAST 09Z-12Z AND MOVING
THROUGH THE INTERIOR OF WESTERN WASHINGTON 12Z-15Z.  COOL UNSTABLE
AIR MASS MOVING INTO THE REGION BEHIND THE FRONT WITH SOMEWHAT
ORGANIZED BANDS OF SHOWERS MOVING THROUGH INTO TUESDAY NIGHT.
TEMPERATURES ALOFT COOLING DOWN BEHIND THE FRONT AND BY TUESDAY
NIGHT 850 MB TEMPS AROUND -5C AND 925 MB TEMPS IN THE 0-1C RANGE.
PUTTING THE SNOW LEVEL AROUND 1000 FEET. RIGHT NOW SNOW AMOUNTS IN
THE MOUNTAINS DO NOT LOOK LIKE THEY WILL MEET WARNING CRITERIA. WILL
STAY WITH THE WINTER WEATHER ADVISORY. A SHORT BREAK IN THE
PRECIPITATION POSSIBLE EARLY WEDNESDAY BEFORE THE UPPER LEVEL TROUGH
AXIS SWINGS THROUGH THE AREA WEDNESDAY AFTERNOON FOR ANOTHER ROUND
OF SHOWERS. CURRENT FORECASTS ON TRACK. NO UPDATE THIS EVENING.
FELTON

.LONG TERM...FOR THU AND FRI I HAVE CUT THE POPS A BIT...AND THERE
IS A CHANCE FOR A COUPLE OF PRETTY NICE DAYS...OFFSHORE SFC
GRADIENTS OUGHT TO KEEP THE SHOWERS AT BAY FOR THE MOST PART. BY THE
WEEKEND DISTURBANCES ROTATING THROUGH THE UPPER TROF LOOK A LITTLE
MORE ORGANIZED. THE GFS HAS A STRONG JETSTREAM INTO CALIF WED...THEN
A PAUSE...AND THEN ANOTHER STRONG JET INTO NRN CALIF FOR NEXT
WEEKEND...THAT PRETTY MUCH LEAVES WRN WA IN THE COOL SHOWERY AIR
NORTH OF THE ACTION AND WITH ELY SFC PRES GRADIENTS OVR WRN WA THE
NRN PTN OF SYSTEMS MOVING INTO CALIF AND ORE SHOULD TEND TO DRY UP
ARND HERE. IF I HAD TO PICK ONE SYSTEM THAT MIGHT HOLD TOGETHER IT
WOULD BE THE SYSTEM THAT THE GFS HAS COMING THRU SAT NITE. COOLER
AIR MIGHT START FLOWING DOWN THE FRASER OVER THE WEEKEND...BUT THE
COLD AIR OVER B.C. HAS TO FORM IN PLACE RATHER THAN BEING DRIVEN IN
BY COLD NLY FLOW ALF...AND 1000-850MB THICKNESS ON THE GFS40 IS TOO
WARM FOR SNOW IN THE LOWLANDS SAT NITE SO THE FCST FOR NOW IS PRETTY
STRAIGHTFORWARD...SEASONABLY COOL WITH SHOWERS. 19

&&

.HYDROLOGY...NOW ONLY THE LOWEST REACHES OF MOST RIVERS ARE STILL
ABOVE FLOOD STAGE. THE SKOKOMISH RIVER IS THE ONLY RIVER LEFT ON THE
OLYMPIC PENINSULA ABOVE FLOOD STAGE AND WILL REMAIN ABOVE FLOOD
STAGE INTO TUESDAY.

THE UPPER REACHES OF THE NOOKSACK AND SKAGIT HAVE CRESTED. THE LOWER
REACHES HAVE CRESTED AT MINOR FLOOD LEVELS AND WILL FALL BELOW FLOOD
STAGE ON TUESDAY AS WELL.

THE SNOQUALMIE RIVER HAS FALLEN BELOW FLOOD STAGE AT THE FALLS AND
THE WARNING THERE HAS ENDED. THE SNOQUALMIE AT CARNATION IS SLOWLY
RECEDING THIS EVENING AND WILL NOT FALL BELOW FLOOD STAGE UNTIL
TUESDAY MORNING. THE FLOOD WARNINGS FOR THE SNOHOMISH RIVER WILL
CONTINUE INTO TUESDAY.

THE GREEN RIVER NEAR AUBURN HAS RECEDED BACK BELOW FLOOD STAGE AND
THE WARNING THERE HAS ENDED.

IN SOUTHWEST WASHINGTON MINOR FLOODING IS OCCURING ON THE REACH OF
THE CHEHALIS RIVER DOWNSTREAM OF CENTRALIA THROUGH THURSTON AND
GRAYS HARBOR COUNTIES. THE CHEHALIS WILL CREST THIS EVENING A FEW
FEET BELOW FLOOD STAGE. THE CREST ON THE CHEHALIS...UNIQUELY SLOW
MOVING AMONG THE MAIN STEM RIVERS IN WESTERN WASHINGTON...WILL NOT
MOVE THROUGH ITS LOWER REACHES IN GRAYS HARBOR COUNTY UNTIL TUESDAY.

PLEASE SEE OUR FLOOD STATEMENTS AND WARNINGS FOR THE MOST UP TO DATE
DETAILS. THOSE BULLETINS GIVE SPECIFIC FLOOD WARNING AND RIVER
FORECASTS FOR EACH RIVER FORECAST POINT.

THE THREAT OF LANDSLIDES WILL CONTINUE BUT GRADUALLY DECREASE OVER
THE NEXT FEW DAYS. A SPECIAL WEATHER STATEMENT DETAILS THE INCREASED
RISK.

PRECIPITATION OVERNIGHT WILL BE MOSTLY SNOW IN THE CASCADES AND
SHOULD NOT AFFECT RIVER FLOWS MUCH. ONE EXCEPTION IS THE SKOKOMISH
BASIN. HERE AN INCH OR TWO OF RAIN IS LIKELY...AND COULD HAVE THE
EFFECT OF KEEPING THE SKOKOMISH RIVER ABOVE FLOOD STAGE SOMEWHAT
LONGER. FELTON/BURKE

&&

.AVIATION...LIGHT TO MODERATE RAIN IS EXPECTED TONIGHT ACROSS W WA
AS A COLD FRONT ADVANCES EAST. FROPA TIMING OFF THE NAM12 IS AROUND
09Z COAST AND 12Z INTERIOR. LOOKS ON TRACK BASED ON SATELLITE. THERE
WERE A FEW LIGHTNING STRIKES OFFSHORE AND MAY SEE AN ISOLATED STRIKE
ALONG THE COAST TONIGHT. IN ADDITION...ANTICIPATE GUSTY S/SE SURFACE
FLOW WITH THE PASSING OF THIS SYSTEM. HIGHEST WINDS WILL BE FOUND
ALONG THE COAST AND NORTH INTERIOR.

CIGS WILL LOWER INTO MAINLY THE 1-2K FT RANGE OVERNIGHT WITH THIS
SYSTEM. VSBYS WILL BE MAINLY RESTRICTED BY PRECIP AND MIST BUT
SHOULD REMAIN AT OR ABOVE 2SM. EXPECT CIGS TO LIFT INTO THE 3-5K FT
RANGE BEHIND THE FRONT BUT AREAS OF CIGS NEAR 2K FT WILL
PERSIST...MAINLY WITH SHOWERS. THE CASCADES WILL BECOME COMPLETELY
OBSCURED. 33

KSEA...ALREADY SEEING LIGHT TO MOD RAIN THIS EVENING...BUT COVERAGE
WILL BECOME MORE WIDESPREAD AS A COLD FRONT MOVES INLAND. AS A
RESULT...CIGS WILL LOWER TO MVFR RANGE. SOUTH WINDS WILL ALSO
INCREASE TONIGHT AND REMAIN GUSTY THROUGH TUE AFTERNOON. 33

&&

.MARINE...A COLD FRONT WILL TRACK EAST THROUGH THE COASTAL WATERS
TONIGHT THEN MOVE INLAND EARLY TUE MORNING. SOUTHERLY WINDS WILL
RISE TO GALE FORCE STRENGTH OVER THE COASTAL WATERS AND WEST
ENTRANCE OF JUAN DE FUCA. EXPECT SCA SOUTH/SOUTHEAST WINDS ACROSS
REMAINING ZONES. WINDS WILL EASE LATE TUE AFTERNOON OR EARLY
EVENING...HOWEVER MAY NEED TO STRETCH THE SCA IN PUGET SOUND/HOOD
CANAL THROUGH TUE EVE AS SLY PRES GRADIENT REMAINS TIGHT. MODELS
SHOW ANOTHER TROUGH MOVING IN ON WED...WITH STRONGER S/SE OFFSHORE
FLOW DEVELOPING THU OR FRI. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNINGS REMAIN IN EFFECT FOR PARTS OF THE CWA.

     A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE OLYMPICS AND
     CASCADES FROM 9 PM TONIGHT THROUGH TUESDAY EVENING.

PZ...GALE WARNINGS REMAIN IN EFFECT FOR THE COASTAL WATERS AND
     WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.

     A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS IS
     IN EFFECT FROM LATE TONIGHT THROUGH WED NIGHT.

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