046  
FXUS02 KWBC 300657  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
156 AM EST TUE NOV 30 2021  
 
VALID 12Z FRI DEC 3 2021 - 12Z TUE DEC 7 2021  
   
..OVERVIEW
 
 
A QUASI-ZONAL FLOW PATTERN IS EXPECTED TO BE IN PLACE TO CLOSE OUT  
THE WORK WEEK ACROSS THE NORTHERN TIER STATES WITH A PRONOUNCED  
TROUGH EXITING THE EAST COAST. BY THE WEEKEND, AN UPPER RIDGE  
AXIS TRIES TO BECOME ESTABLISHED OVER THE WEST COAST AND THE  
EASTERN PACIFIC, AND A TROUGH AMPLIFIES WITH DEVELOPING SURFACE  
LOW OVER THE PLAINS. THIS WILL LIKELY BE FOLLOWED BY A SECOND  
WELL ORGANIZED STORM SYSTEM BY THE END OF THE FORECAST PERIOD  
ACROSS THE WESTERN HIGH PLAINS, WITH A ZONAL FLOW PATTERN ACROSS  
THE EASTERN HALF OF THE NATION.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE 00Z MODEL GUIDANCE SUITE IS IN DECENT AGREEMENT ON FRIDAY  
BEFORE MORE NOTICEABLE DIFFERENCES EMERGE BY SATURDAY, WITH THE  
GFS INDICATING A FLATTER TROUGH OVER THE GREAT LAKES AND  
NORTHEAST, AND THE ENSEMBLE MEANS ARE NOT CAPTURING THE MAGNITUDE  
OF THE INCOMING TROUGH ACROSS THE PACIFIC NORTHWEST THAT WILL  
EVENTUALLY LEAD TO AN ORGANIZED LOW PRESSURE SYSTEM OVER THE  
PLAINS BY SUNDAY MORNING. THE CMC HAS TRENDED MORE IN LINE WITH  
THE MODEL CONSENSUS COMPARED TO PREVIOUS DAYS ACROSS THE WESTERN  
U.S., AND IS REASONABLY CLOSE TO THE GFS AND ECMWF WITH PORTRAYING  
THE NEXT TROUGH/STORM SYSTEM ARRIVING ON THE WEST COAST BY MONDAY  
NIGHT. BY THE END OF THE FORECAST PERIOD, THE GFS IS CONSIDERABLY  
STRONGER AND SLOWER WITH THE TROUGH APPROACHING THE EAST COAST.  
 
THE WPC FORECAST WAS PRIMARILY BASED ON A CMC/ECMWF/GFS BLEND  
THROUGH SATURDAY. THEREAFTER, INCREASED WEIGHTING TOWARDS THE  
ENSEMBLE MEANS WHILST KEEPING SOME OF THE OPERATIONAL GFS AND  
ECMWF.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
WEATHER SHOULD BE RELATIVELY UNEVENTFUL IN TERMS OF RAINFALL OR  
SNOW RELATED HAZARDS WITH NOT MUCH IN THE WAY OF HEAVY  
PRECIPITATION CURRENTLY EXPECTED THROUGH EARLY SUNDAY. ROUNDS OF  
RELATIVELY LIGHT PRECIPITATION ARE FORECAST FOR THE MIDWEST, GREAT  
LAKES, AND NORTHEAST WITH A PROGRESSIVE STORM TRACK OVER THE  
REGION. MOISTURE INCREASING AHEAD OF A COLD FRONT IS EXPECTED TO  
RESULT IN SCATTERED SHOWERS AND A FEW THUNDERSTORMS FROM THE DEEP  
SOUTH TO THE OHIO VALLEY OVER THE WEEKEND, BUT AMOUNTS ARE NOT  
CURRENTLY EXPECTED TO BE EXCESSIVE. A SHORTWAVE AND COLD FRONT  
REACHING THE PACIFIC NORTHWEST BY SUNDAY NIGHT AND THROUGH MONDAY  
IS EXPECTED TO RESULT IN ANOTHER ROUND OF MODERATE TO LOCALLY  
HEAVY RAIN AND MOUNTAIN SNOWS TO WESTERN WASHINGTON AND OREGON,  
WITH SOME OF THIS MOISTURE REACHING THE NORTHERN ROCKIES BY  
TUESDAY WITH HEAVY SNOW POSSIBLE FOR THE HIGHER ELEVATIONS OF  
NORTHERN IDAHO, WESTERN MONTANA, AND WESTERN WYOMING.  
 
TEMPERATURES ARE EXPECTED TO BE ABOVE NORMAL FOR EARLY DECEMBER  
ACROSS MOST OF THE NATION THROUGH EARLY NEXT WEEK, WITH THE  
GREATEST POSITIVE ANOMALIES EXPECTED FOR THE CENTRAL AND SOUTHERN  
PLAINS ON FRIDAY WHERE HIGHS ARE FORECAST TO BE 15 TO 25 DEGREES  
ABOVE AVERAGE. ANOTHER EPISODE OF WELL ABOVE NORMAL TEMPERATURES  
IS LIKELY FOR THE WESTERN HIGH PLAINS ON MONDAY AHEAD OF THE NEXT  
COLD FRONT. A FEW LOCATIONS MAY APPROACH DAILY RECORD HIGHS WITH  
THESE MILD TEMPERATURES. ON THE OTHER END OF THE SPECTRUM, COLD  
WEATHER IS FORECAST TO CONTINUE ACROSS THE NORTHEAST U.S. WITH  
HIGHS RUNNING UP TO 10 DEGREES BELOW NORMAL THROUGH THE WEEKEND  
WITH A COLD UPPER LEVEL TROUGH OVERHEAD. HOWEVER, NO MAJOR ARCTIC  
AIRMASS INTRUSIONS ARE EXPECTED DURING THIS FORECAST PERIOD.  
 
HAMRICK  
 
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, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE AT:  
 
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/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page