905  
FXUS01 KWBC 010820  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
319 AM EST FRI DEC 01 2017  
 
VALID 12Z FRI DEC 01 2017 - 12Z SUN DEC 03 2017  
   
..HEAVY SNOW OVER THE NORTHERN CASCADES
 
 
   
..SNOW POSSIBLE OVER THE SOUTHERN CASCADES AND NORTHERN ROCKIES
 
 
   
..HEAVY RAIN POSSIBLE OVER PARTS OF THE NORTHWEST COAST
 
 
THE UPPER-LEVEL PATTERN HAS A GENERALLY WEST TO EAST FLOW REGIME  
THROUGH SATURDAY WHEN THE FLOW PATTERN BECOMES MORE AMPLIFIED OVER  
THE PACIFIC NORTHWEST. EMBEDDED IN THE FAST UPPER-LEVEL FLOW,  
WEAK DISTURBANCES OVER THE SOUTHEAST WILL AID IN PRODUCING  
SCATTERED RAIN OVER THE AREA THROUGH SATURDAY EVENING. IN THE  
MEANTIME, AN UPPER-LEVEL DISTURBANCE OVER THE NORTHEAST WILL MOVE  
EASTWARD OUT OVER THE WESTERN ATLANTIC BY FRIDAY EVENING. RAIN  
WILL DEVELOP OVER PARTS OF NEW ENGLAND THAT WILL BEGIN TO TAPER  
OFF BY FRIDAY AFTERNOON AND END BY FRIDAY EVENING.  
 
MEANWHILE, UPPER-LEVEL ENERGY OVER NORTHERN ROCKIES WILL MOVE  
EASTWARD TO THE GREAT LAKES WHILE INTENSIFYING. THE ENERGY WILL  
PRODUCE AREAS OF RAIN AND SNOW OVER PARTS OF THE UPPER GREAT LAKES  
OVERNIGHT FRIDAY INTO SATURDAY THAT WILL MOVE INTO EASTERN CANADA  
BY SATURDAY EVENING.  
 
ADDITIONALLY, WEAK EMBEDDED UPPER-LEVEL IMPULSES WILL AID IN  
PRODUCING RAIN OVER THE PACIFIC NORTHWEST COAST AND SNOW OVER THE  
HIGHER ELEVATIONS OF THE NORTHERN ROCKIES ON FRIDAY MORNING. ON  
FRIDAY, UPPER-LEVEL TROUGHING WILL BEGIN TO MOVE ONSHORE OVER THE  
PACIFIC NORTHWEST THAT WILL SLOWLY INCREASE AS AN UPPER-LEVEL LOW  
COMES ONSHORE OVER THE NORTHWEST ON SATURDAY AFTERNOON INTO  
EVENING. WEAK ONSHORE FLOW WILL ALSO ACCOMPANY THE UPPER-LEVEL  
TROUGHING. AS THE TROUGHING MOVES ONSHORE, THE SNOW LEVEL WILL  
LOWER OVER THE PACIFIC NORTHWEST. RAIN AND HIGHER ELEVATION SNOW  
WILL DEVELOP OVER THE PACIFIC NORTHWEST THROUGH SATURDAY EVENING.  
ON SATURDAY, THE RAIN WILL BEING TO MOVE INTO NORTHERN CALIFORNIA  
WITH THE PRECIPITATION EXTENDING INLAND TO THE NORTHERN ROCKIES BY  
SATURDAY EVENING. SNOW WILL DEVELOP OVER THE HIGHER ELEVATIONS OF  
NORTHERN/CENTRAL CALIFORNIA INTO PARTS OF THE SIERRAS SATURDAY  
EVENING INTO SATURDAY NIGHT. SNOW WILL ALSO DEVELOP OVER PARTS OF  
THE NORTHERN ROCKIES BY SATURDAY EVENING.  
 
ZIEGENFELDER  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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