880  
FXUS02 KWBC 170700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EST FRI NOV 17 2017  
 
VALID 12Z MON NOV 20 2017 - 12Z FRI NOV 24 2017  
   
..PATTERN OVERVIEW AND GUIDANCE/UNCERTAINTY PREFERENCES...
 
 
RECENT GFS/ECMWF/CMC RUNS CLUSTER FAIRLY WELL AND PROGRESS A  
DYNAMIC MID-UPPER LEVEL TROUGH/HEIGHT FALLS FROM THE UPPER MIDWEST  
THROUGH THE GREAT LAKES/NERN US TUE-WED WITHIN NRN STREAM FLOW.  
HOWEVER...THE RECENT UKMET RUNS OFFER A MORE DIGGY/AMPLIFIED  
SOLUTION THAT HAS SOME POTENTIAL GIVEN UPSTREAM RIDGE  
AMPLIFICATION. GEFS/ECMWF ENSEMBLE MEANS ARE IN BETWEEN AND  
HEAVILY WEIGHTED IN THE WPC FORECAST GIVEN UNCERTAINTY. THIS  
SUPPORTS A DEEPENED CLIPPER LOW TRACK AND SWATH OF PCPN ALONG THE  
US/CANADIAN BORDER ALONG WITH A REINFORCING COOLING SURGE AND A  
PERIOD OF LAKE EFFECT SNOWS IN THE WAKE OF SYSTEM PASSAGE.  
 
THE EXTENT OF DIGGING OF EMBEDDED SRN STREAM IMPULSES UNDERNEATH  
TO THE LEE OF A BUILDING WARMING WRN US MID-UPPER LEVEL RIDGE  
EARLY NEXT WEEK AND MID-LATER NEXT WEEK POTENTIAL SRN STREAM  
TROUGH/LOW SEPARATION OVER THE GULF COAST CAN FURTHER COMPLICATED  
BY POTENTIAL FOR NRN STREAM INTERACTION WITH SOME SOLUTIONS.  
FORECAST SPREAD AND UNCERTAINTY REMAINS ABOVE NORMAL ALONG WITH  
MODEL RUN TO RUN VARIANCE. PREFER ECMWF ENSEMBLES THAT SHOW MORE  
MODEST FLOW SEPARATION AND WEATHER FOCUS THAN THE ECMWF...BUT MUCH  
MORE THAN THE GFS/GEFS. THAT SEEMS REASONABLE GIVEN OVERALL FLOW  
AMPLIFICATION UPSTREAM AND RECENT OVERALL MODEL TRENDS.  
 
MEANWHILE...CONTINUED INLAND FLOW OF ERN PACIFIC IMPULSES FROM AN  
AMPLIFIED OFFSHORE MID-UPPER LEVEL MEAN TROUGH WILL PROLONG A WET  
PATTERN INCLUDING ELEVATION SNOWS OVER THE NWRN US THROUGH NEXT  
MIDWEEK. FORECAST SPREAD AND UNCERTAINTY GROWS RAPIDLY INTO  
THANKSGIVING AROUND WHEN THE POTENTIAL EXISTS FOR SOME BULK OF  
THIS TROUGH ENERGY TO WORK TO THE COAST ALONG WITH LEAD MOISTURE  
PLUME TAP THAT COULD FUEL ENHANCED PCPN.  
 
SCHICHTEL  
 

 
 
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