775  
FXUS02 KWBC 021600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT THU NOV 02 2017  
 
VALID 12Z SUN NOV 05 2017 - 12Z THU NOV 09 2017  
   
..OVERVIEW WITH WEATHER/THREAT HIGHLIGHTS
 
 
THE UPPER PATTERN OVER THE LOWER 48 WILL BE DRIVEN BY UPPER RIDGES  
OVER MEXICO AND WELL UPSTREAM NEAR ALASKA WITH TROUGHING IN  
BETWEEN...CENTERED OVER THE NWRN US. A COUPLE OF SYSTEMS PUSH  
THROUGH THE WEST DURING THE PERIOD WITH COOLER TEMPERATURES AND  
WIDESPREAD RAIN AND SNOW. THE ERN STATES TREND TOWARD LOWER  
HEIGHTS AS A LEAD FRONT PUSHES OFFSHORE MON. A SERIES OF UNCERTAIN  
AND PCPN FOCUSING WAVES ALONG THE FRONT LIFT THROUGH THE CENTRAL  
US THEN MID-ATLC/SE US NEXT WEEK THAT MAY DEVELOP OFFSHORE.  
POST-FRONTAL COOLING HIGH PRESSURE ALSO FILTERS OVER MUCH OF THE  
CENTRAL AND ERN US MID-LATE NEXT WEEK TO SUPPLANT SOME RECORD  
PRE-FRONTAL WARMTH OVER THE US SRN TIER STATES EARLIER IN THE  
WEEK.  
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MODELS AND ENSEMBLES REMAIN WELL CLUSTERED TO START THE FORECAST  
ON SUN/MON...LENDING A COMPOSITE 06 UTC GFS/GEFS AND 00 UTC  
ECMWF/ECMWF ENSEMBLES BLEND THAT OFFERS GOOD CONTINUITY AND  
FORECASTER CONFIDENCE. HOWEVER...SOLUTIONS DIVERGE RAPIDLY DAYS  
5-7. GUIDANCE CONTINUES TO SHOW QUITE VARIED SOLUTIONS ALOFT WITH  
RESPECT TO THE AMPLITUDE AND TIMING OF MAIN TROUGH ENERGY PATTERN  
EVOLUTIONS OVER THE NERN PACIFIC AND IN ADVANCE IN RESPONSE OUT  
THROUGH THE WRN US/ROCKIES TO THE CENTRAL THEN ERN US WITH LEAD  
TROUGH ENERGIES. ACCORDINGLY...THERE ARE SIGNIFICANT RUN TO RUN  
INCONSISTENCIES WITH ASSOCIATED SURFACE SYSTEM REFLECTIONS AND  
SENSIBLE WEATHER/THREATS FOCUS. THE 00 UTC GFS IS MUCH MORE  
PROGRESSIVE THAN THE 00 UTC ECMWF...BUT THE 06 UTC GFS IS LESS  
PROGRESSIVE THAN THE ECMWF.  
THE 00 UTC UKMET/CANADIAN AND SOME ENSEMBLE MEMBERS ALSO OFFER  
POTENTIAL FOR A MORE PINCHED/OFFSHORE NERN PACIFIC CLOSED LOW. WPC  
MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS FOR DAYS  
5-7 (TUE-NEXT THU) WERE PRIMARILY ENSEMBLE MEAN BASED TO  
DE-EMPHASIZE THE LESS PREDICTABLE EMBEDDED FEATURES UNTIL BETTER  
CLUSTERING EVOLVES. THE POTENTIAL IS STILL THERE THOUGH FOR ANY OF  
THESE SHORTWAVE ALOFT BASED LOWS TO DEVELOP FURTHER THAN IN WPC  
PROGS. LEANED MORE WEIGTHING ON THE ECMWF ENSEMBLE MEAN THAT  
MAINTAINS FLOW AMPLITUDE LONGER THAN RECENT GEFS RUNS.  
 
SCHICHTEL  
 

 
 
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