694  
FXUS02 KWBC 310505  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
104 AM EDT TUE OCT 31 2017  
 
VALID 12Z FRI NOV 03 2017 - 12Z TUE NOV 07 2017  
   
..COLDER AND STORMY FOR THE WEST
 
 
   
..OVERVIEW AND GUIDANCE PREFERENCES
 
 
RATHER PERSISTENT UPPER PATTERN OF STRONG RIDGING IN WESTERN  
ALASKA AND OVER MEXICO COMBINED WITH AN UPPER LOW JUST WEST OF THE  
DAVIS STRAIT WILL SUPPORT TROUGHING IN THE WESTERN STATES INTO  
SOUTHERN CANADA THROUGH THE PERIOD. THE RECENT GFS/ECMWF AND THEIR  
ENSEMBLE MEANS FORMED A GOOD CONSENSUS. USED A MAJORITY ENSEMBLE  
MEAN WEIGHTING BY NEXT MONDAY AS THERE REMAINS DISAGREEMENT ON HOW  
THE TROUGH EJECTS OUT OF THE WEST (I.E., SPEED AND SHAPE OF  
EMBEDDED VORTICITY WITHIN THE FLOW).  
   
..WEATHER HIGHLIGHTS
 
 
A STRONG COLD FRONT WILL MOVE THROUGH THE NORTHWEST AND  
INTERMOUNTAIN WEST FRI/SAT BEFORE LIFTING THROUGH THE HIGH PLAINS  
SUNDAY. THE SOUTHERN PORTION OF THE FRONT WILL WORK THROUGH  
CALIFORNIA AND THE DESERT SOUTHWEST SAT-TUE. TO THE EAST, LEAD  
COLD FRONT WILL EXIT THE NORTHEAST BUT LEAVE ITS SOUTHERN  
EXTENSION BACK ACROSS THE CAROLINAS AND TN/OH VALLEY BEFORE  
LIFTING NORTHWARD AS A WARM FRONT AS THE PACIFIC SYSTEM MOVES  
THROUGH THE WESTERN GREAT LAKES. THE WESTERN BOUNDARY WILL  
SEPARATE COLD ARCTIC AIR (TEMPERATURES 10-25F BELOW AVERAGE)  
ACROSS MUCH OF MONTANA FROM MUCH MILDER AIR ACROSS THE  
CENTRAL/SOUTHERN PLAINS AND DEEP SOUTH (10-20F ABOVE AVERAGE)  
UNTIL A FRONT APPROACHES EARLY NEXT WEEK. THE ENTIRE WEST WILL SEE  
COOLER TEMPERATURES WITH TIME AND MOST AREAS WILL SEE AT LEAST  
SOME PRECIPITATION, FOCUSED ACROSS CENTRAL/NORTHERN CALIFORNIA AND  
THE INTERIOR WEST. HEAVY SNOW IS LIKELY FOR FAVORED AREAS IN  
HIGHER TERRAIN WITH WINDY CONDITIONS AS THE TROUGH PASSES THROUGH.  
 
FRACASSO  
 

 
 
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