708  
FXUS02 KWBC 071600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST THU DEC 07 2017  
 
VALID 12Z SUN DEC 10 2017 - 12Z THU DEC 14 2017  
   
..A MIDWEST/GREAT LAKES THROUGH NERN US HEAVY SNOW THREAT
 
 
...PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT..  
 
THE 06 UTC GFS/GEFS AND 00 UTC ECMWF/ECMWF ENSEMBLES OFFER A WELL  
CLUSTERED FORECAST SOLUTION THAT IMPLIES BELOW NORMAL UNCERTAINTY  
OVERALL DESPITE MODEST RUN TO RUN VARIABLILITY. A FAVORED  
COMPOSITE SOLUTION LOCKS IN A FULL LATITUDE WRN NORTH AMERICAN  
RIDGE/ERN NORTH AMERICAN TROUGH PATTERN ALOFT. THIS WILL CONTINUE  
A SYNOPTIC PATTERN OVER THE U.S. WITH MILD/DRY CONDITIONS IN THE  
WEST...A TRANSITION ZONE OF TEMPS IN THE PLAINS TO MS VALLEY...AND  
COLD FLOW INTO THE ERN THIRD OF THE NATION WHERE HEAVY SNOW  
POTENTIAL WILL FOCUS FROM THE MIDWEST/GREAT LAKES TO THE NRN  
MID-ATLANTIC/NORTHEAST.  
 
THIS PATTERN WILL BE HIGHLIGHTED BY A SERIES OF POTENT SHORTWAVES  
AND ATTENDANT CLIPPER SYSTEMS/SNOW SWATHS THAT WILL DIG TO THE LEE  
OF THE WRN NOAM ACROSS THE UPPER MIDWEST AND MIDWEST/GREAT LAKES  
AND OUT ACROSS THE ERN US WITHIN THE ERN US TROUGH. REINFORCED  
COLD AIR ADVECTION WILL ALSO ENHANCE LAKE EFFECT SNOWS IN THE WAKE  
OF SYSTEM PASSAGES THAT DO OFFER SOME TIMING VARIANCE. ONE LOWS  
ALSO HAS AMPLE POTENTIAL TO FURTHER DEVELOP TUE-WED AS A POTENTIAL  
COASTAL STORM. THIS OFFERS A THREAT FOR HEAVY SNOW IN THE COLD AIR  
BACK FROM THE NRN MID-ATLANTIC THROUGH THE NORTHEAST.  
 
SCHICHTEL  
 

 
 
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