143  
FXUS01 KWBC 182027  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
327 PM EST MON DEC 18 2017  
 
VALID 00Z TUE DEC 19 2017 - 00Z THU DEC 21 2017  
   
..HEAVY SNOW POSSIBLE OVER THE CASCADES AND NORTHERN ROCKIES
 
 
   
..HEAVY RAIN POSSIBLE OVER PARTS OF THE PACIFIC NORTHWEST COAST
 
 
...HEAVY RAIN POSSIBLE OVER PORTIONS OF THE SOUTHERN PLAINS INTO  
THE SOUTHERN APPALACHIANS...  
 
ONSHORE FLOW AHEAD OF THE NEXT SYSTEM WILL AID IN PRODUCING RAIN  
AND HIGHEST ELEVATION SNOW OVER PARTS OF THE PACIFIC NORTHWEST AND  
SNOW AND LOWER ELEVATIONS RAIN OVER PARTS OF THE NORTHERN  
INTERMOUNTAIN REGION/NORTHERN ROCKIES THROUGH TUESDAY MORNING. ON  
TUESDAY THE NEXT SYSTEM WILL BEGIN TO MOVE ONSHORE OVER THE  
PACIFIC NORTHWEST MOVING INLAND TO THE NORTHERN ROCKIES/GREAT  
BASIN AND PARTS OF CENTRAL CALIFORNIA BY WEDNESDAY. THE SNOW  
LEVELS WILL DECREASE OVER THE NORTHWEST AS THE ASSOCIATED FRONT  
MOVES INLAND, LOWERING TO THE COAST OVER PARTS OF NORTHWESTERN  
WASHINGTON STATE. RAIN AND HIGHER ELEVATIONS SNOW WILL DEVELOP  
OVER THE NORTHWEST AND SNOW OVER THE NORTHERN INTERMOUNTAIN  
REGION/NORTHERN ROCKIES ON TUESDAY. RAIN AND HIGHER ELEVATION  
SNOW BEGINS TO MOVE INTO NORTHERN CALIFORNIA BY TUESDAY EVENING  
THAT WILL EXPAND INTO CENTRAL CALIFORNIA AND SNOW IN THE GREAT  
BASIN OVERNIGHT TUESDAY INTO WEDNESDAY. IN ADDITION, SNOW WILL  
BEGIN TO DEVELOP OVER PARTS OF THE NORTHERN PLAINS ALSO OVERNIGHT  
TUESDAY INTO WEDNESDAY.  
 
MEANWHILE, AN UPPER-LEVEL LOW OVER NORTHWESTERN MEXICO WILL MOVE  
NORTHEASTWARD TO THE LOWER MISSISSIPPI VALLEY BY WEDNESDAY WHILE  
WEAKENING. MOISTURE FROM THE WESTERN GULF OF MEXICO WILL STREAM  
NORTHWARD OVER THE SOUTHERN PLAINS INTO PARTS OF THE LOWER  
MISSISSIPPI VALLEY AND INTO THE SOUTHEAST BY WEDNESDAY MORNING.  
THE MOISTURE AND UPPER-LEVEL ENERGY WILL AID IN PRODUCING SHOWERS  
AND THUNDERSTORMS OVER PARTS OF THE WESTERN GULF COAST/SOUTHERN  
PLAINS THAT WILL BEGIN TO EXPAND EASTWARD INTO THE LOWER  
MISSISSIPPI VALLEY BY TUESDAY MORNING. ON TUESDAY, THE SHOWERS  
AND THUNDERSTORMS WILL CONTINUE TO EXPAND EASTWARD INTO PARTS OF  
THE TENNESSEE VALLEY/SOUTHEAST WELL INTO WEDNESDAY MORNING.  
 
MORE TO FOLLOW  
 
ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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