793  
FXUS01 KWBC 291939  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
238 PM EST SAT DEC 29 2018  
 
VALID 00Z SUN DEC 30 2018 - 00Z TUE JAN 01 2019  
 
...A NEW PACIFIC STORM SYSTEM WILL BRING LOCALLY HEAVY SNOW ACROSS  
THE PACIFIC NORTHWEST AND THE ROCKIES...  
 
...MUCH COLDER THAN NORMAL TEMPERATURES WILL BE FOCUSED OVER MUCH  
OF THE WEST AND HIGH PLAINS GOING THROUGH NEW YEAR'S EVE...  
 
...VERY MILD TEMPERATURES WILL ARRIVE ACROSS PORTIONS OF THE  
SOUTHERN AND EASTERN U.S. ALONG WITH A NEW STORM SYSTEM THAT WILL  
BRING ADDITIONAL HEAVY RAIN AND THUNDERSTORMS...  
 
A NEW STORM SYSTEM DROPPING IN ACROSS THE PACIFIC NORTHWEST WILL  
ADVANCE GRADUALLY SOUTHEAST AND INLAND ACROSS THE INTERMOUNTAIN  
REGION FOR TONIGHT AND SUNDAY. THIS WILL BRING A NEW ROUND OF RAIN  
ALONG THE COAST AND SOME HEAVY SNOW FOR THE HIGHER TERRAIN  
INCLUDING THE CASCADES AND THE CENTRAL AND NORTHERN ROCKIES. SOME  
LOCATIONS OVER THE FAR NORTHERN ROCKIES INCLUDING THE BITTERROOTS  
WILL SEE AS MUCH AS 1 TO 2 FEET OF NEW SNOW GOING THROUGH SUNDAY.  
BY NEW YEAR'S EVE, THE MOISTURE AND ENERGY ASSOCIATED WITH THIS  
SYSTEM WILL THEN QUICKLY ADVANCE EAST OUT ACROSS THE NORTHERN  
PLAINS AND THE UPPER MIDWEST. A STRIPE OF LIGHT TO MODERATE SNOW  
AND PERHAPS EVEN SOME FREEZING RAIN WILL IMPACT THESE AREAS MAKING  
FOR LOCALLY HAZARDOUS TRAVEL CONDITIONS. MEANWHILE, MUCH COLDER  
AIR WILL FILTER SOUTH IN BEHIND THIS SYSTEM WITH MANY AREAS OF THE  
INTERMOUNTAIN WEST AND THE HIGH PLAINS HIGH TEMPERATURES WELL  
BELOW FREEZING AND AS MUCH AS 15 TO 25 DEGREES BELOW NORMAL.  
 
FARTHER EAST, THE WEATHER WILL AGAIN TEND TO TREND MUCH MILDER AND  
WETTER, AS A STORM SYSTEM DEVELOPS OVER THE LOWER MISSISSIPPI  
VALLEY REGION ON NEW YEAR'S EVE AND LIFTS NORTH UP ACROSS THE  
LOWER GREAT LAKES REGION. SOUTHERLY FLOW AHEAD OF A LOW CENTER AND  
ATTENDANT COLD FRONT WILL RESULT IN NOTABLY WARMER TEMPERATURES  
LIFTING NORTH FROM THE GULF COAST STATES AND OVERSPREADING MUCH OF  
THE EASTERN HALF OF THE NATION. HIGH TEMPERATURES ESPECIALLY ALONG  
AND JUST WEST OF THE APPALACHIANS INCLUDING THE TENNESSEE AND OHIO  
VALLEYS WILL BE AS MUCH AS 15 TO 25 DEGREES ABOVE NORMAL ON NEW  
YEAR'S EVE. WITH THE INFLUX OF WARMER AIR WILL ALSO BE A  
SUBSTANTIAL AMOUNT OF MOISTURE, AND THE EXPECTATION IS FOR A  
RATHER WIDESPREAD AREA OF HEAVY RAINFALL AND EMBEDDED  
THUNDERSTORMS TO IMPACT THE SOUTHERN AND EASTERN U.S. FROM THE  
LOWER AND MIDDLE MISSISSIPPI VALLEY EAST TO THE OHIO VALLEY AND  
MID-ATLANTIC REGION. SOME LOCALIZED RUNOFF AND FLOODING CONCERNS  
WILL BE POSSIBLE GIVEN RAINFALL AMOUNTS OF AS MUCH AS 1 TO 3  
INCHES WITH THIS NEXT SYSTEM, AND BASED ON THIS, THE WEATHER  
PREDICTION CENTER HAS ISSUED A MARGINAL RISK OF EXCESSIVE  
RAINFALL. IN ADDITION TO THE RAINFALL, THERE WILL BE A LOCALIZED  
CONCERN FOR SOME SEVERE WEATHER, ESPECIALLY ACROSS THE GULF COAST  
STATES, AND THIS IS WHERE THE STORM PREDICTION CENTER HAS  
HIGHLIGHTED A MARGINAL RISK OF SEVERE THUNDERSTORMS. THE CONCERNS  
FOR HEAVY RAINFALL AND SEVERE WEATHER WILL BOTH NEED TO BE CLOSELY  
MONITORED OVER THE NEXT COUPLE OF DAYS.  
 
ORRISON  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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