198  
FXUS02 KWBC 011847  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
147 PM EST SUN DEC 1 2024  
 
VALID 12Z WED DEC 04 2024 - 12Z SUN DEC 08 2024  
 
...ANOTHER BLAST OF ARCTIC COLD IN THE CENTRAL AND EASTERN U.S.  
LATER THIS WEEK...  
   
..HEAVY LAKE EFFECT SNOW TO CONTINUE THROUGH WEDNESDAY
 
 
   
..OVERVIEW
 
 
MEAN UPPER LEVEL TROUGHING OVER THE CENTRAL AND EASTERN U.S. WILL  
DOMINATE THE WEATHER PATTERN THROUGH THIS WEEK INTO NEXT WEEKEND,  
AND WEATHER SYSTEMS WILL BE DRIVEN BY SHORTWAVE TROUGHS ROTATING  
AROUND THE BROAD UPPER LEVEL TROUGH. A COUPLE COLD FRONTS WILL PUSH  
SOUTH ACROSS THE EASTERN TWO-THIRDS OF THE NATION THIS WEEK AND  
WILL BRING ANOTHER BLAST OF COLD ARCTIC AIR. THIS PATTERN WILL ALSO  
FAVOR LAKE EFFECT SNOW IN THE GREAT LAKES, BUT THE HEAVIEST SHOULD  
COME TO AN END MID TO LATER THIS WEEK. ELSEWHERE, HIGH PRESSURE  
WILL PERSIST IN THE WEST BEFORE A FRONTAL SYSTEM APPROACHES NEXT  
WEEKEND, AND MOIST RETURN FLOW FROM THE GULF WILL SUPPORT DAILY  
RAIN CHANCES ALONG THE GULF COAST.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
MODELS SHOW FAIRLY GOOD AGREEMENT THROUGH MUCH OF THE PERIOD ON  
THE OVERALL LARGE SCALE FLOW. CONFIDENCE HAS INCREASED IN A BIT  
FASTER PROGRESSION OF THE COLD FRONT THROUGH THE EAST LATE THIS  
WEEK, USHERING IN ANOTHER ROUND OF ARCTIC AIR FOR PARTS OF THE  
NORTHERN PLAINS, MIDWEST, AND INTO THE EAST. THE NEXT SHORTWAVE  
INTO THE NORTH-CENTRAL U.S. ON FRIDAY SHOULD BE WEAKER BUT DOES  
SHOW SOME UNCERTAINTY IN TERMS OF TIMING. THE CMC WAS NOTABLY  
FASTER WITH THIS AND WAS NOT USED IN THE BLEND BEYOND DAY 4. OUT  
WEST, THE GUIDANCE SHOWS THE RIDGE SHIFTING EAST NEXT WEEKEND, BUT  
SOME UNCERTAINTY IN THE TIMING OF A COLD FRONT INTO THE NORTHWEST.  
 
THE WPC FORECAST BLEND WAS ANCHORED BY THE ECMWF THROUGH THE FIRST  
HALF OF THE PERIOD, WITH SMALLER CONTRIBUTIONS FROM THE  
GFS/UKMET/CMC. AFTER DAY 5, BEGAN INCREASING USAGE OF THE ENSEMBLE  
MEANS THROUGH DAY 7 TO ACCOUNT FOR INCREASING UNCERTAINTY.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
 
LAKE EFFECT SNOW IS FORECAST TO CONTINUE THIS WEEK AS A CLIPPER  
LOW PRESSURE SYSTEM MOVES ACROSS THE REGION WEDNESDAY AND THURSDAY  
FOLLOWED BY STRONG WEST-NORTHWESTERLY WINDS. SIGNIFICANT SNOW  
ACCUMULATIONS WILL BE POSSIBLE IN FAVORED DOWNWIND LOCATIONS, AND  
TRAVEL CONDITIONS WILL LIKELY BE HAZARDOUS, ESPECIALLY EARLIER IN  
THE PERIOD. SNOW WILL ALSO BE POSSIBLE ELSEWHERE IN THE NORTHEAST  
AS THE CLIPPER SYSTEM MOVES THROUGH, ESPECIALLY IN THE HIGHER  
TERRAIN OF THE APPALACHIANS. CONDITIONS SHOULD IMPROVE BRIEFLY LATE  
THIS WEEK, BUT ANOTHER LOW PRESSURE SYSTEM WILL BRING ANOTHER  
CHANCE FOR WINTRY PRECIPITATION TO THE REGION NEXT WEEKEND.  
 
THE REST OF THE NATION WILL BE MAINLY DRY THIS WEEK WITH A COUPLE  
EXCEPTIONS. MOIST RETURN FLOW FROM THE GULF WILL RESULT IN DAILY  
RAIN CHANCES ALONG THE GULF COAST AND INTO PORTIONS OF THE SOUTH.  
THERE WILL LIKELY BE ENOUGH INSTABILITY TO SUPPORT LOCALLY HEAVY  
RAINFALL ON WEDNESDAY IN PORTIONS OF SOUTHEAST TEXAS AND LOUISIANA,  
AND THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THESE  
AREAS. THE RISK OF HEAVY RAINFALL WILL DECREASE THURSDAY THROUGH  
THE END OF THE WEEK AS INSTABILITY DECREASES AND PRECIPITATION  
BECOMES MORE SPREAD OUT ACROSS THE GULF COAST REGION AS FRONTS MOVE  
THROUGH. PRECIPITATION CHANCES WILL ALSO RETURN TO THE NORTHWEST  
LATE THIS WEEK INTO NEXT WEEKEND AS A PACIFIC FRONTAL SYSTEM  
APPROACHES AND PUSHES INLAND.  
 
TEMPERATURES WILL DROP BELOW NORMAL FOR PARTS OF THE NORTH-CENTRAL  
TO EASTERN U.S. THIS WEEK AS A COLD FRONT USHERS IN ANOTHER BLAST  
OF ARCTIC AIR. DAYTIME HIGHS FROM THE UPPER MIDWEST INTO THE EAST  
COULD BE 10-20 DEGREES BELOW NORMAL. ELSEWHERE, TEMPERATURES WILL  
BE MILD FOR THIS TIME OF YEAR, GENERALLY NEAR TO SLIGHTLY ABOVE  
AVERAGE WITH THIS MILDER AIR GRADUALLY EXPANDING EAST WITH TIME.  
 
SANTORELLI/DOLAN  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM  
RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
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