423  
FXUS01 KWBC 192028  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
328 PM EST TUE DEC 19 2017  
 
VALID 00Z WED DEC 20 2017 - 00Z FRI DEC 22 2017  
   
..HEAVY SNOW POSSIBLE OVER THE SOUTHERN CASCADES
 
 
...SNOW OVER THE NORTHERN/CENTRAL ROCKIES, NORTHERN PLAINS, AND  
GREAT LAKES...  
 
...HEAVY RAIN POSSIBLE OVER PARTS OF THE LOWER MISSISSIPPI VALLEY  
INTO THE TENNESSEE VALLEY/SOUTHERN APPALACHIANS...  
 
UPPER-LEVEL ENERGY OVER TEXAS WILL MOVE EASTWARD OFF THE SOUTHERN  
MID-ATLANTIC COAST BY EARLY THURSDAY MORNING. MOISTURE FROM THE  
WESTERN GULF OF MEXICO WILL MOVE INLAND OVER THE WESTERN GULF  
COAST/LOWER MISSISSIPPI VALLEY AND INTO PARTS OF THE SOUTHEAST  
THROUGH WEDNESDAY EVENING. RAIN AND THUNDERSTORMS WILL DEVELOP  
OVER PARTS OF THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI  
VALLEY/TENNESSEE VALLEY THAT WILL EXPAND EASTWARD INTO THE  
SOUTHERN MID-ATLANTIC BY WEDNESDAY MORNING. THE RAIN AND  
THUNDERSTORMS WILL COME TO AN END, WEST TO EAST, STARTING  
WEDNESDAY MORNING INTO THURSDAY.  
 
MEANWHILE, A STRONG UPPER-LEVEL TROUGH OVER THE NORTHWEST WILL  
MOVE SOUTHEASTWARD TO THE GREAT BASIN/SOUTHWEST BY THURSDAY. THE  
ENERGY WILL AID IN PRODUCING RAIN AND HIGHER ELEVATION SNOW OVER  
THE PACIFIC NORTHWEST AND SNOW OVER THE NORTHERN INTERMOUNTAIN  
REGION/NORTHERN ROCKIES. OVERNIGHT TUESDAY, RAIN AND HIGHER  
ELEVATION SNOW WILL EXPAND INTO PARTS OF NORTHERN CALIFORNIA AND  
CENTRAL CALIFORNIA BY WEDNESDAY AFTERNOON. SNOW WILL ALSO EXPAND  
INTO THE GREAT BASIN AND THE NORTHERN HIGH PLAINS ALSO OVERNIGHT  
TUESDAY. THE RAIN AND HIGHER ELEVATION SNOW WILL BEGIN TO END  
OVER THE PACIFIC NORTHWEST BY WEDNESDAY EVENING AND OVER PARTS OF  
THE NORTHERN ROCKIES/GREAT BASIN BY THURSDAY. IN ADDITION, LIGHT  
SNOW WILL MOVE INTO THE NORTHERN PLAINS ON WEDNESDAY MORNING AND  
MOVE INTO THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES BY  
THURSDAY. THE SNOW WILL ALSO EXPAND INTO PARTS OF THE CENTRAL  
ROCKIES/SOUTHWEST OVERNIGHT WEDNESDAY INTO THURSDAY.  
 
ELSEWHERE, UPPER-LEVEL ENERGY MOVING ACROSS THE GREAT LAKES INTO  
NORTHERN NEW ENGLAND WILL MOVE OUT OVER THE WESTERN ATLANTIC BY  
WEDNESDAY EVENING. THE ENERGY WILL AID IN DEVELOPING LIGHT SNOW  
OVER PARTS OF THE UPPER GREAT LAKES INTO NEW ENGLAND THAT WILL  
SLOWLY TAPER OFF TO LAKE EFFECT SNOW OVER THE UPPER GREAT LAKES BY  
WEDNESDAY MORNING. BY WEDNESDAY EVENING, THE LAKE EFFECT SNOW  
WILL COME TO AN END.  
 
ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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