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HYDROMETEOROLOGICAL DISCUSSION 
NORTHWEST RIVER FORECAST CENTER PORTLAND OR 
11:30 AM PST MON NOV 23 2009 

HYDROMETEOROLOGICAL CONDITIONS...PAST 24 HOURS...4 AM - 4 AM 

WIDESPREAD WRAP-AROUND MIXED SHOWERS PIVOTED AROUND A LOW SHIFTING OUT OF  
EASTERN WASHINGTON EASTWARD TOWARD THE MISSOULA FORECAST AREA. HEAVIEST 0.8  
TO AROUND 1.5 INCH VALLEY RAIN AND MOUNTAIN SNOW TENDED TO CONCENTRATE MAINLY 
ALONG THE WASHINGTON CASCADES...WITH MORE WIDELY SCATTERED SIMILAR AMOUNTS 
HITTING THE NORTH-CENTRAL IDAHO PANHANDLE...AS WELL AS THROUGH THE SOUTHWEST 
FLANK OF THE SAWTOOTH MOUNTAINS. FREEZING LEVELS THIS MORNING RANGED FROM 
THE SURFACE AT SPOKANE...3500 FEET AT BOISE...3800 FEET AT QUILLAYUTE... 
AND 9000 FEET AT MEDFORD.  

OBSERVED HYDROLOGIC CONDITIONS 

SOME MINOR WESTERN WASHINGTON AND NORTHWESTERN OREGON STREAM RISES TENDED  
TO TRANSITION INTO MOSTLY FLAT TO RECEDING FLOWS ELSEWHERE. 
  
HYDROMETEOROLOGICAL FORECAST...NOV 23 - NOV 27 

MONDAY AFTERNOON STRONG WARM FRONTAL RAIN PREVIOUSLY HAMMERING VANCOUVER  
ISLAND STARTS SAGGING SOUTHEASTWARD AND TRANSITIONS INTO A COLD FRONT THAT  
CLIPS WESTERN WASHINGTON WITH SOME OCCASIONAL MODERATE MIXED PRECIPITATION 
INTO EARLY TUESDAY MORNING. TUESDAY AFTERNOON TO WEDNESDAY MORNING A RIDGE  
SHIFTING EASTWARD ACROSS OUR FORECAST AREA LARGELY SHUTS OFF PRECIPITATION  
ACROSS THE REGION. WEDNESDAY AFTERNOON A PACIFIC FRONTAL DISTURBANCE SIMILAR 
TO MONDAY'S SYSTEM...EVENTUALLY SAGS SOUTH ALONG THE BRITISH COLUMBIA COAST  
INTO WESTERN WASHINGTON. THIS FRONTAL PUSH INITIALLY WILL INITIALLY HAVE HIGH  
FREEZING LEVELS...AROUND 7000 PLUS FEET...AND IS FORECAST TO GENERATE OCCASIONAL  
MODERATE RAIN ACROSS WESTERN WASHINGTON INTO WEDNESDAY EVENING. AS WE HEAD INTO  
THANKSGIVING DAY ON THURSDAY THIS COLD FRONT TENDS TO DIMINISH AS IT EXTENDS  
SOUTHWARD AND DRIFTS VERY SLOWLY IN ACROSS WESTERN OREGON WHILE STALLING OUT  
ACROSS ACROSS WASHINGTON. THIS DIMINISHING PATTERN GRADUALLY SHIFTS IN ACROSS  
THE EASTSIDE THROUGH FRIDAY...WHILE A FOLLOWING WAVE OF UNSETTLED PACIFIC  
WEATHER RESUMES SOME OCCASIONAL MIXED PRECIPITATION ACROSS OUR WESTSIDE BASINS. 
  
FUTURE HYDROLOGIC CONDITIONS 

LOOK FOR SOME RECURRING MINOR WESTERN WASHINGTON RISES THROUGH THURSDAY 
THAT TRAIL OFF ACROSS WESTERN OREGON LATER IN THE WEEK. OTHERWISE...FLOWS  
TEND TO REMAIN MOSTLY FLAT AND UNRESPONSIVE. 

6-10 DAY OUTLOOK...NOV 28 - DEC 02 

LATEST LONGRANGE MODEL GUIDANCE CONTINUES TO CONVERGE ON A FAIRLY STRONG  
BLOCKING DRY RIDGE SOLUTION OVER THE PACIFIC NORTHWEST FOR THE MAJORITY OF  
THE PERIOD. IF THIS VERIFIES...LOOK FOR A RESULTING DROP OFF IN NATURAL FLOWS  
ACROSS THE REGION.    

GREEN RIVER 

LOOKS LIKE SOME OCCASIONAL MODERATE RAIN THIS MONDAY NIGHT AND AGAIN  
THURSDAY (THANKSGIVING) NIGHT TO FRIDAY. OTHERWISE...THE GREEN RIVER BASIN  
GETS LITTLE IN THE WAY OF HYDROLOGIC FORCING OUT TO THE END OF THIS COMBINED  
FORECAST (OUT THROUGH NEXT WEDNESDAY, DECEMBER 2).  

ML/BA/RV 

VISIT US ON THE WEB AT HTTP://WWW.NWRFC.NOAA.GOV FOR DETAILED 
GRAPHICAL PRECIPITATION...FREEZING LEVEL...AND TEMPERATURE FORECASTS. 

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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 23, 2009
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