815  
FXUS02 KWBC 220700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST WED NOV 22 2017  
 
VALID 12Z SAT NOV 25 2017 - 12Z WED NOV 29 2017  
 
...GUIDANCE/UNCERTAINTY ASSESSMENT AND PATTERN/WEATHER THREAT  
HIGHLIGHTS...  
 
AN ACTIVE PATTERN REMAINS IN PLACE FOR THE PACIFIC NORTHWEST/NRN  
CA AND THE NRN INTERMOUNTAIN WEST/ROCKIES AS A SERIES OF ERN  
PACIFIC IMPUSLES LIFT INLAND INTO AN AMPLIFIED/WARMING LEAD  
W-CENTRAL US MID-UPPER LEVEL RIDGE POSITION. A LEAD CLIPPER SYSTEM  
WILL ALSO DELIVER A MIX OF RAIN AND SNOW TO THE UPPER  
MIDWEST/GREAT LAKES ON FRIDAY/SATURDAY...WITH SNOW LINGERING  
ACROSS THE LOWER GREAT LAKES AND INTERIOR NEW ENGLAND BY THE END  
OF THE WEEKEND. THE FOCUS OF ACTIVE WEATHER BY CYBER MONDAY WILL  
BE WITH AN AMPLIFIED TROUGH THAT REACHES THE WEST COAST. UNSETTLED  
WEATHER WORKS ACROSS THE WRN US/ROCKIES EARLY NEXT WEEK THEN WITH  
HEIGHT FALLS INTO THE CENTRAL THEN E-CENTRAL US INTO NEXT  
MIDWEEK...SPAWNING SURFACE SYSTEM GENESIS AND ADDITIONAL MODEST  
PCPN FOCUS. FARTHER SOUTH...FL WILL FINALLY BE WANING OFF A WET  
PATTERN IN TIME FOR THIS WEEKEND AS A FRONTAL LOW LIFTS OFFSHORE.  
 
MODELS AND ENSEMBLES ARE IN GOOD AGREEMENT WITH THE SYNOPTIC  
PATTERN EVOLUTION OVER THE NEXT WEEK. THERE ARE LINGERING  
DIFFERENCES WITH TIMING AND AMPLITUDE WITH THE EMBEDDED SMALL  
SCALE SYSTEMS...BUT ASSOCIATED SURFACE SYSTEM REFLECTIONS AND  
WEATHER FOCUS ARE BETTER CLUSTERED NOW. FORECAST SPREAD HAS  
DECREASED COMPARED TO THE LAST FEW DAYS AND THE WPC MEDIUM RANGE  
PRODUCT SUITE IS MAINLY DERIVED FROM A COMPOSITE BLEND OF THE  
REASONABLY COMPATABLE 18/00 UTC GFS/GEFS MEAN AND THE 12 UTC  
ECMWF/ECMWF ENSEMBLES.  
 
SCHICHTEL  
 

 
 
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