295  
FXUS02 KWBC 230704  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
203 AM EST THU NOV 23 2017  
 
VALID 12Z SUN NOV 26 2017 - 12Z THU NOV 30 2017  
   
..GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN/THREAT HIGHLIGHTS
 
 
LEAD MID-UPPER LEVEL TROUGH AND SURFACE LOW/FRONTAL SYSTEM/MODEST  
PCPN EJECTS FROM THE NERN US SUN TO THE CANADIAN MARITIMES BY  
CYBER MON. MEANWHILE...THE UPSTREAM PATTERN REMAINS AMPLIFIED  
ALOFT AS AN ENERGETIC ERN PACIFIC TROUGH THREATENS THE WEST COAST.  
THE MODELS NO LONGER OFFER A WELL CLUSTERED ENVELOPE OF SOLUTIONS  
WITH THE FORECAST STRENGTH/TIMING OF THIS FEATURE DAYS 3-7. MODEL  
RUN TO RUN CONTINUITY BECAME ABYSMAL TODAY WITH THE GFS MORE  
PROGRESSIVE THAN EARLIER RUNS AND THE ECMWF LESS PROGRESSIVE AND  
MORE DIGGY/AMPLIFIED. GIVEN ABOVE NORMAL UNCERTAINTY...PREFER AN  
ENSEMBLE MEAN APPROACH USING THE 12 UTC ECMWF ENSEMBLE MEAN AND TO  
A MUCH LESSER EXTENT THE 18 UTC GEFS MEAN. CONSIDERING WATER VAPOR  
FLOW/UPSTREAM FLOW AMPLITUDE AND CONTINUITY HOWEVER...OPTED TO  
LEAN STRONGLY ON ECMWF ENSEMBLES THAT OFFER LESS PROGRESSION/MORE  
AMPLITUDE THAN GEFS/NAEFS...ALBEIT NOT AS MUCH AS THE 12 UTC  
ECMWF. THE NEWER 00 UTC ECMWF HAS EASED FROM 12 UTC ECMWF  
AMPLITUDE. THIS FEATURE IS THE KEY TO THE SUBSEQUENT DOWNSTREAM  
FLOW EVOLUTION NEXT WEEK IN A PATTERN THAT GUIDANCE SEEMS TO BE  
EXTREMELY SENSITIVE TO THE DETAILS OF MID-UPPER LEVEL SUPPORT TO  
LEAD TO SURFACE CYCLOGENESIS  
AND ASSOCIATED MODESTLY EMERGING FRONT MOISTURE/PCPN FOCUS. THE  
WPC SOLUTION WOULD PROVIDE UNSETTLED WEATHER AND PCPN SWATH SEWD  
ACROSS THE WRN US MON INTO TUE...WITH IMPROVING WEATHER AND  
WARMING OVER MUCH OF THE WEST IN ITS WAKE UNDER A BUILDING RIDGE  
ALOFT. CONTINUED MID-UPPER LEVEL TROUGH EJECTION AND EXPANDING  
POTENTIAL WILL THEN BE HIGHLIGHTED ACROSS THE CENTRAL TO ERN US  
TUE-NEXT THU AT WHICH TIME NEW BUT UNCERTAIN PACIFIC ENERGIES  
POTENTIALLY APPROACH THE WEST COAST.  
 
SCHICHTEL  
 

 
 
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