575  
FXUS01 KWBC 232000  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 PM EST SUN DEC 23 2018  
 
VALID 00Z MON DEC 24 2018 - 00Z WED DEC 26 2018  
 
...HEAVY LOW ELEVATION RAIN/MOUNTAIN SNOW EXPECTED ACROSS WESTERN  
OREGON AND NORTHERN/NORTH-CENTRAL CALIFORNIA CHRISTMAS EVE...  
 
...MODERATE TO HEAVY SNOW POSSIBLE OVER THE SIERRA AND CENTRAL  
GREAT BASIN ON CHRISTMAS DAY...  
 
...DEVELOPING STORM TO BRING POTENTIAL TRAVEL TROUBLE OVER THE  
CENTRAL U.S. BEGINNING WEDNESDAY...  
 
UNSETTLED WEATHER IS LIKELY FOR MUCH OF THE WESTERN THIRD OF THE  
LOWER 48 OVER THE NEXT COUPLE OF DAYS AS A SERIES OF PACIFIC STORM  
SYSTEMS MOVES ACROSS THE REGION. THE FIRST SYSTEM CURRENTLY  
PUSHING INLAND IS WEAKENING RATHER QUICKLY, AND WILL BRING MOSTLY  
LIGHT PRECIPITATION TO THE PACIFIC NORTHWEST, NORTHERN CALIFORNIA  
EASTWARD INTO THE NORTHERN ROCKIES THROUGH THE REMAINDER OF TODAY  
AND TONIGHT. ASSOCIATED WITH THIS SYSTEM, WINTER WEATHER  
ADVISORIES ARE POSTED FOR THE CASCADES AND SECTIONS OF THE  
NORTHERN ROCKIES. A MUCH STRONGER SYSTEM IS EXPECTED TO REACH THE  
COAST ON CHRISTMAS EVE AND BRING HEAVY LOW ELEVATION RAIN AND  
MOUNTAIN SNOWS TO MUCH OF WESTERN OREGON SOUTHWARD THROUGH  
NORTHERN AND NORTH-CENTRAL CALIFORNIA. THE HEAVIEST SNOW  
TOTALS...LOCALLY UP TO A FOOT OR MORE...ARE EXPECTED OVER THE  
SOUTHERN OREGON CASCADES, SHASTAS AND NORTHERN/CENTRAL SIERRA FROM  
MONDAY THROUGH MONDAY NIGHT. THIS STORM WILL CONTINUE TO  
STRENGTHEN AS MOVES INTO THE SOUTHWESTERN U.S. BY LATER CHRISTMAS  
DAY. AS A RESULT, PRECIPITATION WILL SPREAD SOUTHWARD THROUGH  
CALIFORNIA AND INLAND ACROSS THE GREAT BASIN...SOUTHWEST AND  
SOUTHERN ROCKIES DURING CHRISTMAS. SNOW LEVELS WITH THIS STORM  
ARE FAIRLY LOW, SO ASIDE FROM COASTAL AREAS AND LOWER ELEVATIONS  
IN THE SOUTHWEST, MUCH OF THE PRECIPITATION WILL BE IN THE FORM OF  
SNOW. HEAVIEST SNOW WILL BE OVER THE CENTRAL SIERRA AND HIGHER  
TERRAIN OF THE GREAT BASIN, BUT SHOULD BEGIN BREAKING OUT OVER THE  
SOUTHERN ROCKIES BY CHRISTMAS NIGHT.  
 
DURING LATE TUESDAY AND WEDNESDAY, THIS SYSTEM WILL PUSH OUT INTO  
THE ROCKIES AND HIGH PLAINS AND BEGIN TO TAP SOME DEEP GULF OF  
MEXICO MOISTURE. AS A RESULT, HEAVY SNOW IS LIKELY FOR MUCH OF  
THE SOUTHERN/CENTRAL ROCKIES NORTHEASTWARD INTO THE NORTHERN AND  
CENTRAL PLAINS STATES, WITH POTENTIALLY HEAVY RAIN AND  
THUNDERSTORMS FARTHER SOUTH THROUGH THE SOUTHERN PLAINS. THIS MAY  
RESULT IN SOME POST-HOLIDAY TRAVEL DIFFICULTIES DURING THE MIDDLE  
OF THE WEEK.  
 
FARTHER EAST, A QUICK-MOVING AND RELATIVELY WEAK FRONTAL SYSTEM  
MOVING THROUGH THE EASTERN U.S. WILL SUPPORT RAIN SHOWERS OVER THE  
CENTRAL MID-ATLANTIC REGION, WITH LIGHT SNOW ACCUMULATIONS  
POSSIBLE FROM THE CENTRAL APPALACHIANS NORTHWARD INTO NEW YORK AND  
SOUTHERN NEW ENGLAND THROUGH SUNDAY EVENING AND DURING THE  
OVERNIGHT HOURS. MEANWHILE...ANOTHER WEAK AREA OF LOW PRESSURE  
ALONG AN ARCTIC BOUNDARY IS LIKELY TO BRING MOSTLY LIGHT  
LAKE-ENHANCED SNOW SHOWERS THROUGH CHRISTMAS EVE TO THE UPPER  
PENINSULA OF MICHIGAN AND NORTHERN LOWER MICHIGAN.  
 
LATER ON MONDAY EVENING THROUGH CHRISTMAS DAY, A QUICK-MOVING WEAK  
UPPER LEVEL SYSTEM WILL TAP INTO A BIT OF RETURNING GULF OF MEXICO  
MOISTURE TO BRING THE CHANCE FOR LIGHT RAIN SHOWERS TO THE MIDDLE  
AND LOWER MISSISSIPPI VALLEY. FARTHER NORTH ACROSS THE UPPER  
MIDWEST, TEMPERATURES SHOULD BE COLD ENOUGH FOR A LITTLE LIGHT  
SNOW, BUT ACCUMULATIONS ARE EXPECTED TO BE LIGHT (IN THE 1-2 INCH  
RANGE).  
 
KLEIN  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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