221  
FXUS01 KWBC 221941  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
240 PM EST SAT DEC 22 2018  
 
VALID 00Z SUN DEC 23 2018 - 00Z TUE DEC 25 2018  
 
...UNSETTLED WEATHER CAN BE EXPECTED WITH LOCALLY HEAVY RAIN FOR  
THE COASTAL RANGES OF THE PACIFIC NORTHWEST AND NORTHERN  
CALIFORNIA OVER THE NEXT COUPLE OF DAYS...  
 
...HEAVY SNOWFALL IS LIKELY FOR THE CASCADES, NORTHERN  
SIERRA-NEVADA AND THE NORTHERN ROCKIES...  
 
IN THE WAKE OF A DEEP LOW CENTER EXITING THE NORTHEAST, THERE WILL  
BE A RETURN TO COLDER TEMPERATURES AND AT LEAST SOME DRIER WEATHER  
GOING THROUGH SUNDAY. HOWEVER, THE NEXT STORM SYSTEM WHICH WILL BE  
CROSSING THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY WILL  
MOVE EAST TOWARD THE LOWER GREAT LAKES BY SUNDAY EVENING. THE  
SYSTEM WILL PRODUCE A SWATH OF MAINLY LIGHT SNOW ACROSS PARTS OF  
THE UPPER MIDWEST AND ACROSS THE GREAT LAKES REGION THROUGH SUNDAY  
AFTERNOON AND EVENING. THIS WILL ADVANCE INTO THE CENTRAL  
APPALACHIANS AND PARTS OF NEW YORK AND SOUTHERN NEW ENGLAND ON  
CHRISTMAS EVE. SOME LIGHT RAIN MEANWHILE WILL IMPACT PORTIONS OF  
THE OHIO AND TENNESSEE VALLEYS AS A COLD FRONT CROSSES THE REGION.  
IN THE WAKE OF THIS NEXT SYSTEM WILL BE A SURGE OF MODESTLY COLDER  
AIR, BUT TEMPERATURES FOR MUCH OF THE EASTERN U.S. WILL BE  
ACTUALLY NEAR OR A BIT ABOVE NORMAL OVER THE NEXT FEW DAYS SINCE  
THERE WILL BE A LACK OF COLD HIGH PRESSURE DROPPING SOUTH FROM  
CANADA.  
 
MUCH OF THE ACTIVE WEATHER GOING TOWARD THE CHRISTMAS HOLIDAY WILL  
ACTUALLY BE FOCUSED ACROSS THE WESTERN U.S. WITH AN EMPHASIS ON  
THE PACIFIC NORTHWEST, NORTHERN CALIFORNIA, AND INTERIOR AREAS OF  
THE NORTHERN GREAT BASIN AND NORTHERN ROCKIES. A COLD FRONT WILL  
ALLOW ONE SURGE OF MOISTURE TO ARRIVE OVERNIGHT AND THROUGH SUNDAY  
FOR THE PACIFIC NORTHWEST, WITH LOCALLY HEAVY RAIN FOR THE COASTAL  
RANGES AND HEAVY ACCUMULATING SNOW OVER THE HIGHER TERRAIN OF THE  
CASCADES. THIS MOISTURE AND ENERGY WILL REACH THE NORTHERN ROCKIES  
BY SUNDAY EVENING. MEANWHILE, ON CHRISTMAS EVE, A WAVE OF LOW  
PRESSURE AND ASSOCIATED FRONT WILL BE APPROACHING COASTAL AREAS OF  
OREGON AND SHOULD BRING A SECOND SURGE OF HEAVY RAIN TO THE  
COASTAL RANGES, ALTHOUGH THIS NEXT AXIS OF MOISTURE AND ONSHORE  
FLOW WILL BE FOCUSED FARTHER SOUTH AND SHOULD IMPACT ALL OF  
NORTHERN CALIFORNIA. HEAVY SNOW WILL BE LIKELY FOR THE HIGHER  
TERRAIN OF THE NORTHERN SIERRA-NEVADA AND GRADUALLY THIS SNOW WILL  
IMPACT THE HIGHER TERRAIN OF THE CENTRAL AND NORTHERN ROCKIES BY  
LATE CHRISTMAS EVE.  
 
ELSEWHERE, THE REMAINDER OF THE COUNTRY SHOULD SEE MAINLY DRY  
WEATHER AND TEMPERATURES THAT ARE NEAR OR ABOVE NORMAL.  
 
ORRISON  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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