976  
FXUS01 KWBC 290801  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EST FRI DEC 29 2017  
 
VALID 12Z FRI DEC 29 2017 - 12Z SUN DEC 31 2017  
 
...HEAVY SNOWFALL LIKELY IN THE HIGHER TERRAIN OF THE NORTHERN  
INTERMOUNTAIN WEST AND NORTHERN ROCKIES...  
 
...A REINFORCING SURGE OF ARCTIC AIR IS FORECAST TO OVERSPREAD  
MUCH OF THE EASTERN TWO-THIRDS OF THE U.S. THIS WEEKEND...  
 
A COLD WEATHER PATTERN IS EXPECTED TO PERSIST THROUGH THE WEEKEND.  
MUCH OF THE COUNTRY EAST OF THE ROCKIES HAS ALREADY BEEN IN THE  
GRIP OF AN ARCTIC AIR MASS. ANOTHER REINFORCING SHOT OF ARCTIC IS  
CURRENTLY TAKING SHAPE OVER NORTHWESTERN CANADA AS THE ASSOCIATED  
STRONG HIGH PRESSURE SYSTEM IS FORECAST TO SLIDE SOUTHEASTWARD AND  
DOMINATE THE WEATHER PATTERN ACROSS THE U.S. MAINLAND THROUGH THE  
WEEKEND. HEAVY SNOW IS EXPECTED ACROSS THE CASCADES AND INTO THE  
NORTHERN ROCKIES TODAY BEFORE GRADUALLY TAPERING OFF ON SATURDAY  
AS MOISTURE FROM A PACIFIC SYSTEM MOVES OVER THE COLD AND DENSE  
ARCTIC AIR AT THE SURFACE. AS MUCH AS 2 TO 3 FEET POSSIBLE IN THE  
HIGHEST TERRAIN OF THE WASHINGTON CASCADES AND THE NORTHERN  
ROCKIES BEFORE ENDING SUNDAY MORNING. FARTHER TO THE WEST, HEAVY  
RAINFALL CAN BE EXPECTED FOR COASTAL REGIONS OF THE PACIFIC  
NORTHWEST TODAY INTO TONIGHT.  
 
A CLIPPER TYPE SYSTEM IS EXPECTED TO SEND A SWATH OF LIGHT SNOW  
RAPIDLY FROM THE DAKOTAS INTO THE MIDWEST TODAY, ACROSS THE OHIO  
VALLEY TONIGHT, AND INTO THE NORTHERN MID-ATLANTIC ON SATURDAY  
WITH ONLY LIGHT ACCUMULATIONS EXPECTED. IN THE WAKE OF THIS  
CLIPPER SYSTEM WILL BE THE ARRIVAL OF A REINFORCING SURGE ARCTIC  
AIR FROM CANADA, SENDING TEMPERATURES DOWN TO AS MUCH AS 30 TO 35  
DEGREES BELOW NORMAL WITH AFTERNOON HIGHS OF BELOW ZERO AS FAR  
SOUTH AS NEBRASKA.  
 
MEANWHILE, A WAVE OF LOW PRESSURE IS EXPECTED TO BRING LIGHT RAIN  
INTO EASTERN TEXAS TONIGHT, SPREADING EASTWARD INTO MUCH OF THE  
CENTRAL GULF STATES BY SUNDAY. SOME MIXED PRECIPITATION CAN BE  
EXPECTED NEAR THE NORTHERN EDGE OF THE MOISTURE SHIELD ACROSS  
NORTHERN TEXAS INTO ARKANSAS AND CENTRAL MISSISSIPPI.  
 
ELSEWHERE, LAKE EFFECT SNOWFALL CAN BE EXPECTED DOWNWIND OF THE  
UPPER AND LOWER GREAT LAKES.  
 
KONG  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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