355  
FXUS01 KWBC 200755  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
254 AM EST WED DEC 20 2017  
 
VALID 12Z WED DEC 20 2017 - 12Z FRI DEC 22 2017  
 
...HEAVY RAINFALL TO SPREAD INTO THE SOUTHEAST AND LOWER  
MID-ATLANTIC TODAY...  
 
...LIGHT TO MODERATE ACCUMULATING SNOWFALL POSSIBLE ACROSS PARTS  
OF THE INTERMOUNTAIN WEST, THE ROCKIES, AND INTO THE NORTHERN  
PLAINS WEDNESDAY AND THURSDAY...  
 
...TEMPERATURES ACROSS THE SOUTHERN TIER STATES WILL BE ABOVE  
NORMAL WHILE MUCH OF THE WESTERN U.S. SHOULD BE BELOW NORMAL...  
 
 
SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE DEEP SOUTH THIS  
MORNING WILL CONTINUE TO PUSH EASTWARD TODAY INTO THE SOUTHEAST  
AND LOWER MID-ATLANTIC REGION. THE HEAVIEST RAINFALL IS EXPECTED  
ALONG A FRONTAL BOUNDARY FROM ROUGHLY NORTHERN GEORGIA INTO THE  
CAROLINAS WHERE ISOLATED FLASH FLOODING MAY BE A THREAT.  
CONDITIONS ACROSS THE DEEP SOUTH SHOULD DRY OUT BY THURSDAY, BUT  
HEAVY RAINFALL MAY RETURN BY FRIDAY AS ANOTHER SYSTEM APPROACHES  
FROM THE WEST. TEMPERATURES AHEAD OF THIS SECOND BOUNDARY FROM THE  
SOUTHERN PLAINS TO MIDDLE MISSISSIPPI VALLEY ON THURSDAY COULD BE  
AS MUCH AS 15 TO 25 DEGREES ABOVE AVERAGE.  
 
A DEEP UPPER LEVEL SYSTEM PUSHING THROUGH THE WESTERN U.S. TODAY  
WILL ALLOW FOR RAIN AND MOUNTAIN SNOWS ACROSS MUCH OF THE CENTRAL  
GREAT BASIN, THE FOUR CORNERS REGION, AND INTO THE ROCKIES. SOME  
LIGHT TO MODERATE SNOW ACCUMULATIONS ARE POSSIBLE IN THE MOUNTAINS  
WHERE WINTER WEATHER ADVISORIES ARE CURRENTLY IN EFFECT. THIS  
SYSTEM WILL ALSO USHER IN COOLER WEATHER ACROSS MUCH OF THE  
WESTERN U.S. BY THURSDAY WITH TEMPERATURE ANOMALIES OF 10 TO 20  
DEGREES BELOW NORMAL POSSIBLE FROM PORTIONS OF THE SOUTHWEST TO  
THE CENTRAL HIGH PLAINS.  
 
ACCUMULATING SNOWFALL IS ALSO POSSIBLE ACROSS PORTIONS OF THE  
NORTHERN PLAINS TO THE UPPER GREAT LAKES ON WEDNESDAY AND INTO  
THURSDAY TO THE NORTH OF THE SURFACE LOW ASSOCIATED WITH THE ABOVE  
MENTIONED SYSTEM. A SECOND SURFACE LOW SHOULD DEVELOP ACROSS THE  
CENTRAL PLAINS BY WEDNESDAY NIGHT WHICH SHOULD ALLOW PRECIPITATION  
TO SPREAD INTO PORTIONS OF THE MIDWEST AND THE OHIO VALLEY BY  
THURSDAY. MUCH OF THIS SHOULD BE RAIN FOR THE MIDDLE MISSISSIPPI  
VALLEY AND THE OHIO VALLEY BUT SNOW, A RAIN/SNOW MIX, OR EVEN  
LIGHT FREEZING RAIN WILL BE POSSIBLE TO THE NORTH OF A WARM FRONT  
FROM NORTHERN IOWA INTO LOWER MICHIGAN. BY THURSDAY NIGHT INTO  
EARLY FRIDAY, THIS WINTRY PRECIPITATION IS FORECAST TO MOVE INTO  
PORTIONS OF THE INTERIOR NORTHEAST AND LOWER GREAT LAKES.  
 
SANTORELLI  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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