River Flood Warning 22, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE JAN 6 2009

.SYNOPSIS...A WARM PLUME OF MOISTURE WILL BRING SIGNIFICANT RAINFALL
WITH HIGH SNOW LEVELS THROUGH THURSDAY MORNING. THE POTENTIAL FOR
RIVER AND SMALL STREAM FLOODING WILL INCREASE TONIGHT AND WEDNESDAY.
THE RAIN WILL TAPER LATE WEDNESDAY NIGHT INTO THURSDAY AS A LOW
PRESSURE SYSTEM PUSHES THE MOISTURE SOUTH OF THE AREA. THURSDAY WILL
BE SHOWERY. DRY WEATHER IS LIKELY ON FRIDAY.

&&

.SHORT TERM...THE OVERALL TREND IS NOT LOOKING GOOD WITH SOME VERY
HIGH RAINFALL RATES STARTING TO COME IN THE PAST FEW HOURS. RADAR
STORM TOTAL PRECIP ESTIMATES SO FAR INDICATE ROUGHLY 3-5 INCHES
ALONG THE W SLOPES OF THE CASCADES FROM KING COUNTY NORTHWARD. A
COUPLE OF OB SITES ALSO CONFIRM 12 HOUR AMOUNTS OF 4-5 INCHES WITH
THE HEAVIEST RAINFALL CURRENTLY ACROSS KING COUNTY NORTHWARD. AN
URBAN AND SMALL STREAM FLOOD WARNING WAS ISSUED FOR KING/SNOHOMISH
COUNTIES WITH RAINFALL RATES CURRENTLY NEAR 1 INCH PER HOUR HOUR
ROUGHLY EAST OF THE I-405 CORRIDOR. THE IMMEDIATE I-5 CORRIDOR IS OF
CONCERN AS WELL BUT RAINFALL RATES HAVE BEEN MUCH LESS SO FAR DUE TO
SHADOWING FROM THE OLYMPICS. IF HEAVIER PRECIP FILLS IN ACROSS THE
METRO CORRIDOR THE WARNING MAY NEED TO BE EXPANDED.

GIVEN THE CURRENT RAINFALL RATES...WILL NEED TO BOOST QPF AMOUNTS
FOR SOME OF THE CASCADES FOR THE TONIGHT PERIOD. TOTAL AMOUNTS OF 10
TO 15 INCHES SEEM ALMOST CERTAIN WITH SOME SPOTS POSSIBLY EXCEEDING
20 INCHES OVER THE NEXT 36 HOURS POSSIBLE. RIVERS ARE ALREADY
RESPONDING RAPIDLY WITH THE FIRST ROUND OF WARNINGS ALREADY UP.
REFER TO THE LATEST FLOOD STATEMENTS FOR DETAILS. LATEST HYDRO
MODELS CONTINUE TO PUSH MANY RIVER TO MAJOR FLOOD CATEGORY AND A FEW
POSSIBLY TO NEAR RECORD FLOOD LEVELS. AS HEAVIER PRECIP SHIFTS SOUTH
LATER TONIGHT...RIVERS SOUTH OF KING COUNTY WILL ALSO BEGIN TO
RESPOND QUICKLY. THE CHEHALIS IS OF PARTICULAR CONCERN GIVEN THE
EXPECTED CREST OVER 73 FEET LATE THURSDAY WHICH COULD IMPACT TRAVEL
ALONG I-5 IN THAT AREA.

WINDS HAVE PICKED UP ACROSS THE SOUTHWEST INTERIOR THIS EVENING. THE
NAM-12 SHOWS THIS LASTING THROUGH THE NIGHT SO I DECIDED TO EXPAND
THE WIND ADVISORY TO INCLUDE THE SOUTHWEST INTERIOR AND LOWER
CHEHALIS VALLEY FOR GUSTS TO 50 MPH. THE WINDS MAY EASE A LITTLE
SOON THAN INDICATES...PERHAPS BY DAYBREAK WEDNESDAY BUT WILL LET THE
NEXT SHIFT DECIDE ON WHEN TO END IT. EXPECT WINDS TO BE OFF AND ON
FROM TACOMA-SEATTLE-EVERETT DEPENDING ON WHERE THE SHADOWING SETS UP
THE REST OF THE NIGHT. GUSTY WINDS CAN STILL BE EXPECTED HERE BUT
JUST BORDERLINE WIND ADVISORY WITH MAX GUSTS TO 45 MPH.

RAIN PERSISTS THROUGH THURSDAY MORNING...THEN STARTS TO DECREASE AS
THE ENTIRE TROUGH COMPLEX SHIFTS INLAND. THE GOOD NEWS IS THAT
MODELS SHOW ENOUGH WEAK RIDGING FOR JUST LIGHT BRUSH BY PRECIP
FRIDAY INTO THE WEEKEND. THIS SHOULD ALLOW RIVERS TO START SUBSIDING
OVER THE WEEKEND.

MERCER

&&

.LONG TERM...PREVIOUS DISCUSSION FOLLOWS...SATURDAY BEGINS DRY BUT A
WEAK SYSTEM BRUSHES THE AREA FROM THE NORTH. HAVE MOSTLY BROAD
BRUSHED THE REST OF THE EXTENDED...KEEPING CHANCE POPS AS EURO IS
WETTER THAN GFS. BURKE

&&

.AVIATION...A WARM FRONT HAS MOVED TO THE NORTH OF WESTERN
WASHINGTON. WE NOW HAVE VERY STRONG ONSHORE FLOW GIVING HEAVY RAIN
TO THE MOUNTAINS...COAST...AREAS AROUND THE STRAIT OF JUAN DE
FUCA...AND SOUTH INTERIOR. STRONG FLOW ALOFT WITH WINDS AT 050
26055KT IS INTERACTING WITH THE OLYMPICS AND MOUNTAINS OF VANCOUVER
ISLAND TO GIVE STRONG WINDS AND A RAIN SHADOW TO AREAS OF THE
CENTRAL PUGET SOUND AREA AND NE OF VANCOUVER ISLAND. FLOW ALOFT WILL
DECREASE BY 5-10 KT AFTER ABOUT 15Z WED. THE ONLY AFFECT ON AVIATION
WEATHER WILL BE TO DECREASE SURFACE WINDS BY ABOUT 5 KNOTS AND TO
REDUCE THE INCIDENCE OF LOW LEVEL WIND SHEAR ASSOCIATED WITH
MECHANICAL TURBULENCE...BUT LOW CIGS AND VISIBILITIES AND AREAS OF
HEAVY RAIN AND WINDY CONDITIONS WILL CONTINUE BEYOND 06Z THU.

KSEA...MINOR FLUCTUATIONS AROUND CURRENT CONDITIONS...2SM -RA BR
BKN006 OVC015 WILL PERSIST THRU 12Z THU. CIGS AND VIS MAY BECOME
LOWER AT TIMES IN HEAVIER PRECIPITATION IF THE RAIN SHADOW
ASSOCIATED WITH THE MESO LOW E OF THE OLYMPICS SHIFTS NORTHWARD
SOMEWHAT. ALBRECHT

&&

.MARINE...GALES WARNINGS ARE NOW IN EFFECT THRU WED MORNING FOR THE
COAST...WEST ENTRANCE AND CENTRAL STRAIT...AND PUGET SOUND/HOOD
CANAL. OTHER INLAND WATERS HAVE HIGH END SMALL CRAFT ADVISORIES.
CONDITIONS WILL RELAX A BIT WED AS ONSHORE GRADIENTS DECREASE
SOMEWHAT. A COLD FRONT WILL SLOWLY SAG SOUTH THROUGH LATE WED NIGHT
AND THU AND WILL BE FOLLOWED BY HIGH PRES LATER THU THROUGH FRI.
ALBRECHT

.AVALANCHE...FORECASTS ON TRACK WITH CURRENT HEAVY LOADING AND
RAPIDLY INCREASING STRESS ON A VARIETY OF BURIED WEAK LAYERS. THESE
WEAKNESSES EXIST BOTH WITHIN MORE RECENT SNOWFALL SINCE DEC 31 AND
IN THE VERY WEAK RECRYSTALLIZED SNOW OR FACETS FROM EARLY TO MID
DECEMBER THAT EXIST NEAR THE BASE OF THE OLDER SNOWPACK. OVERALL
IMPACT OF ANTICIPATED VERY HEAVY PRECIPITATION ...MOSTLY AS
RAIN...DURING NEXT 36 HOURS SHOULD BE SEVERE AND EXTREME AVALANCHE
DANGER LIKELY MANIFESTING OVER A SIGNIFICANT PORTION OF OUR NW
AVALANCHE TERRAIN. AS MUCH AS 6-10 INCHES OR MORE OR WATER
EQUIVALENT EXPECTED FROM NOW THROUGH WEDNESDAY NIGHT...WHICH IS
EQUIVALENT TO ADDING 5 TO 10 FEET OR MORE OF SNOW LOAD TO OUR STILL
FRAGILE SNOWPACK AT DEPTH...ALL IN THE SPACE OF TWO DAYS. BEST TO
AVOID AVALANCHE TERRAIN...PRACTICE BEACON SEARCHES...AND USE THIS
OPPORTUNITY TO GET YOUR GEAR READY FOR WHEN THE SNOWPACK ACTUALLY
DOES STABILIZE AND STRENGTHEN. MOORE

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...EXTREME AVALANCHE WARNING IN EFFECT FOR THE OLYMPICS AND
CASCADES THROUGH WEDNESDAY.
FLOOD WATCHES AND WARNINGS IN EFFECT FOR MUCH OF THE AREA FROM THIS
EVENING THROUGH FRIDAY AFTERNOON.
WIND ADVISORY IN EFFECT TONIGHT FOR THE SEATTLE AND EVERETT
METROPOLITAN AREA...EAST PUGET SOUND LOWLANDS...SOUTHWEST
INTERIOR...AND THE HOOD CANAL AREA.

PZ...GALE WARNING IN EFFECT FOR THE COASTAL WATERS...WEST ENTRANCE
TO THE STRAIT OF JUAN DE FUCA...PUGET SOUND AND HOOD CANAL.
SMALL CRAFT ADVISORY IN EFFECT FOR THE REMAINING WATERS.
SMALL CRAFT ADVISORY IN EFFECT FOR SEVERE GRAYS HARBOR BAR.

WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
911 PM PST TUE JAN 06 2009

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

0910 PM     HEAVY RAIN       3 WNW SEKIU             48.28N 124.37W
01/06/2009  M2.11 INCH       CLALLAM            WA   TRAINED SPOTTER

            4 HOUR TOTAL

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1000 PM PST TUE JAN 06 2009

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

0959 PM     HEAVY RAIN       1 NE FORKS              47.96N 124.38W
01/06/2009  M3.05 INCH       CLALLAM            WA   TRAINED SPOTTER

            TOTAL IN 22 HOURS. RECENT RAIN RATE 0.75 IN. AN HOUR

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1155 PM PST TUE JAN 06 2009

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

0723 PM     HEAVY RAIN       1 SSW GRASSMERE         48.53N 121.79W
01/06/2009  M5.08 INCH       SKAGIT             WA   TRAINED SPOTTER

            24 HOUR RAINFALL 5.08 INCHES. RAINING 0.2 INCHES PER HOUR
            NOW. STILL 12 INCHES OF COMPACT SNOW ON GROUND.

&&

ALBRECHT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1204 AM PST WED JAN 07 2009

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

1204 AM     HEAVY RAIN       1 NE FORKS              47.96N 124.38W
01/07/2009  M3.50 INCH       CLALLAM            WA   TRAINED SPOTTER

            24 HR TOTAL

&&