815  
FXUS01 KWBC 290816  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
316 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  
AIR 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. MEANWHILE, HEAVY SNOW IS EXPECTED  
TO FALL 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 OF SNOW IS 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 OF  
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 TO CONTINUE  
DOWNWIND OF THE GREAT LAKES.  
 
KONG  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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