150  
FXUS02 KWBC 010657  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 AM EDT WED NOV 01 2017  
 
VALID 12Z SAT NOV 04 2017 - 12Z WED NOV 08 2017  
   
..COLDER AND STORMY FOR THE WEST
 
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER/THREAT HIGHLIGHTS
 
 
THE LATEST 12Z GFS/ECMWF/ECMWF ENSEMBLE MEAN AND 18Z GFS/GEFS MEAN  
OFFERED A REASONABLE STARTING POINT TO THE FORECAST. TRENDED AWAY  
FROM THE 12Z GFS/ECMWF MID-PERIOD DUE TO UNCERTAINTY IN HOW  
QUICKLY THE UPPER TROUGH PROGRESSES THROUGH CANADA (TREND HAS BEEN  
QUICKER) AND HOW A SECONDARY SHORTWAVE MODULATES THE WESTERN  
TROUGH AROUND MONDAY. BY NEXT TUE/WED, 18Z GFS AND 12Z ECMWF FELL  
BACK IN LINE WITH THEIR ENSEMBLE MEANS AS YET ANOTHER UPPER LOW  
LOOKS TO RELOAD THE WESTERN TROUGH JUST OFF THE PAC NW COAST. THE  
EAST SHOULD THEN SEE LOWERING HEIGHTS AS THE UPPER RIDGE REMAINS  
OVER MEXICO. PRECIPITATION SHOULD FOCUS ALONG THE WAVY BOUNDARY  
AND SFC LOW THAT LIFTS THROUGH THE GREAT LAKES SUN/MON AND THEN  
SETTLES INTO THE SOUTHEAST TUE/WED. THE WEST STANDS TO SEE  
APPRECIABLE PRECIPITATION NEARLY EVERYWHERE OUTSIDE THE LOWER  
DESERTS OF AZ. THE SIERRAS AND CENTRAL ROCKIES COULD SEE SEVERAL  
FEET OF SNOW OVER THE COURSE OF THE WEEK.  
 
FRACASSO  
 

 
 
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