Product Display for Flood Potential


FGUS76 KSEW 251239 
ESFSEW 
WAC009-027-031-033-041-045-053-057-061-067-073-260045- 

HYDROLOGIC OUTLOOK 
NATIONAL WEATHER SERVICE SEATTLE WA 
439 AM PST WED NOV 25 2009 

...RAINFALL OVER WESTERN WASHINGTON LATER TODAY THROUGH THURSDAY 
NIGHT COULD PUSH THE MOST-FLOOD PRONE RIVERS ABOVE FLOOD STAGE... 

A FRONT WILL MOVE INTO WESTERN WASHINGTON TODAY AND REMAIN STALLED 
OVER THE AREA TONIGHT...THANKSGIVING DAY...AND INTO THURSDAY 
NIGHT. THIS COULD PRODUCE ENOUGH RAIN TO CAUSE FLOODING ON THE 
MOST FLOOD-PRONE RIVER REACHES IN THE AREA. 

THIS INCLUDES...BUT IS NOT NECESSARILY LIMITED TO...THE SKOKOMISH 
RIVER IN MASON COUNTY...THE SNOQUALMIE RIVER NEAR CARNATION IN 
KING COUNTY...THE PUYALLUP RIVER NEAR ORTING IN PIERCE COUNTY... 
AND THE LOWER REACH OF THE CHEHALIS RIVER IN THURSTON AND GRAYS 
HARBOR COUNTIES. 

IF FLOODING DOES OCCUR...IT WILL LIKELY BE MINOR WITH THE POSSIBLE 
EXCEPTION OF THE SKOKOMISH RIVER.  

FLOODING COULD BEGIN ON THE SKOKOMISH RIVER THURSDAY OR THURSDAY 
NIGHT. IF FLOODING OCCURS ON THE SNOQUALMIE OR PUYALLUP RIVERS... 
WHICH FLOW OUT OF THE CASCADES...IT WOULD PROBABLY START THURSDAY 
NIGHT OR FRIDAY. THE LOWER REACH OF THE CHEHALIS RIVER...WHICH 
DRAINS A LARGE AREA OF SOUTHWEST WASHINGTON...WOULD NOT BEGIN 
UNTIL FRIDAY NIGHT OR SATURDAY. 

RAINFALL TOTALS OF 2 TO 4 INCHES ARE LIKELY OVER THE OLYMPIC 
PENINSULA WITH ONE AND A HALF TO 3 INCHES LIKELY OVER THE 
CASCADES. THE SNOW LEVEL WILL BE AROUND 8000 FEET TODAY AND 
GRADUALLY FALL TO 5500 FEET THURSDAY NIGHT. 

RIVERS THROUGHOUT WESTERN WASHINGTON ARE RUNNING HIGHER THAN 
NORMAL DUE TO UNUSUALLY WET WEATHER OVER THE PAST MONTH. THEREFORE 
THE RAINFALL EXPECTED...WHILE NOT EXCEPTIONAL...COULD BE ENOUGH TO 
DRIVE THE MOST FLOOD-PRONE SPOTS ABOVE FLOOD STAGE. 

FLOODING IS NOT EXPECTED ON THE GREEN RIVER. 

$$ 

MCDONNAL


FGUS76 KSEW 250023 CCA 
ESFSEW 
WAC009-027-031-033-041-045-053-057-061-067-073-251500- 

HYDROLOGIC OUTLOOK...CORRECTED 
NATIONAL WEATHER SERVICE SEATTLE WA 
422 PM PST TUE NOV 24 2009 

...POSSIBILITY FOR FLOODING ON SOME WESTERN WASHINGTON RIVERS THURSDAY 
NIGHT INTO FRIDAY... 

A COLD FRONT WILL STALL OVER WESTERN WASHINGTON WEDNESDAY NIGHT 
AND REMAIN IN PLACE INTO THURSDAY NIGHT GENERATING PERIODS OF RAIN 
ACROSS THE REGION. A SURFACE LOW PRESSURE CENTER IS EXPECTED TO 
DEVELOP ALONG THE FRONT WELL WEST OF OREGON THEN MOVE UP THE FRONT 
AND ACROSS THE NORTHWEST EARLY FRIDAY. THIS LOW WILL GENERATE 
ANOTHER PERIOD OF HEAVIER RAIN ACROSS PARTS OF WESTERN WASHINGTON. 
THROUGH THIS PERIOD...FREEZING LEVELS WILL REMAIN HIGH ENOUGH FOR 
MOSTLY RAIN ACROSS THE MOUNTAINS. 

WHERE THE AREAS OF HEAVIER RAIN OCCUR WILL DEPEND UPON ON WHERE 
THE FRONT STALLS AND THE EXACT PATH OF THE LOW THAT IS EXPECTED TO 
MOVE UP THE FRONT. A NORTH OR SOUTH SHIFT OF EITHER WILL MAKE A 
SIGNIFICANT DIFFERENCE ON WHICH AREA RECEIVES THE HEAVIER RAINS. 

UNDER MORE NORMAL CIRCUMSTANCES...THE AMOUNT OF RAIN FORECAST 
WOULD GENERALLY NOT POSE THIS MUCH OF A PROBLEM...BUT RIVERS ARE 
STILL DRAINING WATER FROM THE RECENT RAINS AND COULD RESPOND MORE 
READILY TO ADDITIONAL RAINFALL. 

AT THIS TIME...RIVERS OF CONCERN INCLUDE THE SKOKOMISH ON THE 
OLYMPIC PENINSULA...AND THE FOLLOWING RIVERS FLOWING OFF THE 
CASCADES...THE SNOQUALMIE AT CARNATION...THE PUYALLUP RIVER NEAR 
ORTING AND THE LOWER REACHES OF THE CHEHALIS RIVER. IF MORE RAIN 
FALLS THAN IS CURRENTLY ANTICIPATED THEN A FEW ADDITIONAL RIVERS 
WOULD BE ADDED TO THIS LIST. 

THIS PRECIPITATION PATTERN IS NOT GOOD FOR GENERATING SIGNIFICANT 
RAINS IN THE GREEN RIVER BASIN...SO NO FLOODING IS EXPECTED ON 
THE GREEN RIVER DURING THE PERIOD. 

$$ 

CERNIGLIA


FGUS76 KSEW 242353 
ESFSEW 
WAC009-027-031-033-041-045-053-057-061-067-073-251415- 

HYDROLOGIC OUTLOOK 
NATIONAL WEATHER SERVICE SEATTLE WA 
353 PM PST TUE NOV 24 2009 

...POSSIBILITY FOR FLOODING ON SOME WESTERN WASHINGTON RIVERS THURSDAY 
NIGHT INTO FRIDAY... 

A COLD FRONT WILL STALL OVER WESTERN WASHINGTON WEDNESDAY NIGHT 
AND REMAIN IN PLACE INTO THURSDAY NIGHT GENERATING PERIODS OF RAIN 
ACROSS THE REGION. A SURFACE LOW PRESSURE CENTER IS EXPECTED TO 
DEVELOP ALONG THE FRONT WELL WEST OF OREGON THEN MOVE UP THE FRONT 
AND ACROSS THE NORTHWEST EARLY FRIDAY. THIS LOW WILL GENERATE 
ANOTHER PERIOD OF HEAVIER RAIN ACROSS PARTS OF WESTERN WASHINGTON. 
THROUGH THIS PERIOD...FREEZING LEVELS WILL REMAIN HIGH ENOUGH FOR 
MOSTLY RAIN ACROSS THE MOUNTAINS. 

WHERE THE AREAS OF HEAVIER RAIN OCCUR WILL DEPEND UPON ON WHERE 
THE FRONT STALLS AND THE EXACT PATH OF THE LOW THAT IS EXPECTED TO 
MOVE UP THE FRONT. A NORTH OR SOUTH SHIFT OF EITHER WILL MAKE A 
SIGNIFICANT DIFFERENCE ON WHICH AREA RECEIVES THE HEAVIER RAINS. 

UNDER MORE NORMAL CIRCUMSTANCES...THE AMOUNT OF RAIN FORECAST 
WOULD GENERALLY NOT POSE THIS MUCH OF A PROBLEM...BUT RIVERS ARE 
STILL DRAINING WATER FROM THE RECENT RAINS AND COULD RESPOND MORE 
READILY TO ADDITIONAL RAINFALL. 

AT THIS TIME...RIVERS OF CONCERN INCLUDE THE SKOKOMISH ON THE 
OLYMPIC PENINSULA...AND THE FOLLOWING RIVERS FLOWING OFF THE 
CASCADES...THE SNOHOMISH AT CARNATION...THE PUYALLUP RIVER NEAR 
ORTING AND THE LOWER REACHES OF THE CHEHALIS RIVER. IF MORE RAIN 
FALLS THAN IS CURRENTLY ANTICIPATED THEN A FEW ADDITIONAL RIVERS 
WOULD BE ADDED TO THIS LIST. 

THIS PRECIPITATION PATTERN IS NOT GOOD FOR GENERATING SIGNIFICANT 
RAINS IN THE GREEN RIVER BASIN...SO NO FLOODING IS EXPECTED ON 
THE GREEN RIVER DURING THE PERIOD. 

$$ 

CERNIGLIA

US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Northwest River Forecast Center (NWRFC)
5241 NE 122nd Avenue
Portland, Oregon 97230-1089
Telephone: 503-326-7401

Last Modified: November 25, 2009

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