Green River/Howard Hanson Dam Monitoring

FXUS66 KSEW 241155
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST TUE NOV 24 2009

.HYDROLOGY...AS THE FORECAST STANDS...THE ONLY SIGNIFICANT THREAT OF 
RIVER FLOODING IS FOR THE SKOKOMISH RIVER AS A RESULT OF RAIN THIS 
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. DETAILS FOLLOW.

THE WEAK SYSTEMS AFFECTING THE AREA TODAY AND TONIGHT WILL HAVE 
LITTLE OR NO AFFECT ON WESTERN WASHINGTON RIVERS.
 
PRECIPITATION WILL INCREASE OVER THE OLYMPIC MOUNTAINS WEDNESDAY 
AFTERNOON AND...AS MENTIONED ABOVE...THE WEDNESDAY NIGHT THROUGH 
THURSDAY NIGHT PERIOD WILL BE RATHER WET. IT LOOKS REASONABLE THAT 3 
TO 4 INCHES OF PRECIPITATION WILL FALL OVER THE OLYMPIC MOUNTAINS 
AND PERHAPS THE NORTH CASCADES DURING THAT 36 HOUR PERIOD WITH THE 
SNOW LEVELS FAIRLY HIGH -- PROBABLY FALLING FROM 7000 FT TO AROUND 
4500 FT DURING THE PERIOD. MOST LIKELY THAT AMOUNT OF RAIN WOULD 
PRESENT A FLOOD THREAT ONLY FOR THE SKOKOMISH RIVER.

A BIT LESS PRECIPITATION IS EXPECTED OVER THE CENTRAL CASCADES -- 
LIKELY IN THE 1.5 TO 3 INCH RANGE. AT THE OUTSIDE THAT WOULD PRESENT 
A FLOOD THREAT FOR ONLY THE MOST FLOOD-PRONE RIVER REACHES LIKE THE 
PUYALLUP RIVER NEAR ORTING. 

COOLER SHOWERY WEATHER WILL ARRIVE FRIDAY...AND THE WEATHER LOOKS 
LESS WET IN THE EXTENDED PERIOD FOR SATURDAY AND BEYOND. 

NO FLOODING IS EXPECTED ON THE GREEN RIVER DURING THE PERIOD. 

• Entire Text Forecast Discussion
• Graphical Forecast Discussion
• NWS Seattle Hydrology Page

• Washington Atmospheric River Observatories
  Includes Westport, Spanaway, and Ravensdale

• Water Vapor Trails
• Global Precipitable Water Loop
• Weather Briefing Package (under construction)

• 10-Day Precipitation and Temperature Forecasts
• 3-Day Precipitation Forecasts

• Why all this New Concern for Flooding in the Green River Valley?
• Western Washington Flooding 101 (.pdf file)
• Flood Preparation & Response - Emergency Phone Numbers & Resources (.pdf file)

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