120  
FXUS02 KWBC 211558  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1058 AM EST TUE NOV 21 2017  
 
VALID 12Z FRI NOV 24 2017 - 12Z TUE NOV 28 2017  
   
..OVERVIEW/GUIDANCE PREFERENCES
 
 
THE PRIMARY FEATURES OVER THE NEXT WEEK WILL BE A TROUGH OVER THE  
EAST COAST WITH A STRONG RIDGE OVER THE WEST COAST. THIS RIDGE  
WILL EVENTUALLY BREAK DOWN BY THE BEGINNING OF NEXT WEEK AS A  
TROUGH MOVES OVER THE WEST COAST. FOR MOST OF THE MEDIUM RANGE  
PERIOD...AN ACTIVE PATTERN WILL BE IN PLACE FOR THE PACIFIC  
NORTHWEST... INTERMOUNTAIN WEST...IN ADDITION TO NORTHERN  
CALIFORNIA. FARTHER SOUTH...FLORIDA WILL FINALLY BE WANING OFF A  
WET PATTERN IN TIME FOR THE WEEKEND.  
 
THE MODELS AND ENSEMBLES CONTINUE TO BE IN GOOD AGREEMENT WITH THE  
SYNOPTIC PATTERN OVER THE NEXT WEEK...BUT THERE WERE DIFFERENCES  
WITH TIMING AND AMPLITUDE WITH THE SMALL SCALE SYSTEMS. THE  
BIGGEST CONFLICT WAS THE TIMING OF THE TROUGH COMING INTO THE WEST  
COAST BETWEEN SUNDAY AND MONDAY AND HOW IT EVOLVES MOVING INTO THE  
PLAINS BY TUESDAY. THE OPERATIONAL ECMWF AND EVEN THE GFS HAS  
ALTERNATED BETWEEN A DISTURBANCE MOVING ACROSS THE PLAINS TO A  
RIDGE BEING IN PLACE. HOWEVER...THEIR ENSEMBLES HAVE BEEN  
CONSISTENT WITH THE SLOWER SOLUTION. FOR THE BEGINNING OF THE  
MEDIUM RANGE PERIOD...HAD AN EVEN SPLIT BETWEEN THE 06Z GFS/00Z  
ECMWF AND A SLIGHT WEIGHT TO THEIR ENSEMBLES. BY DAYS 5-7  
(SUN-TUE)...MUCH LESS WEIGHT WAS GIVEN TO THE OPERATIONAL  
GFS/ECMWF AND PUT MORE WEIGHT TOWARD THE 00Z ECENS/NAEFS WITH SOME  
GEFS AS THE NAEFS WAS ALSO CONSISTENT WITH THE EVOLUTION OF THE  
FRONTAL SYSTEM MOVING INTO THE PLAINS BY MIDWEEK.  
   
..WEATHER HIGHLIGHTS
 
 
AS A COLD FRONT PUSHES SOUTHWARD ACROSS FLORIDA ON FRIDAY AND INTO  
SATURDAY...HEAVY RAINFALL WILL PERSIST ON FRIDAY AND COMPLETELY  
CLEARING OUT BY SATURDAY. DEPENDING ON HOW CLOSE THE SURFACE LOW  
MOVES ALONG THE EAST COAST...THE CAROLINAS COULD SEE SOME LIGHT TO  
MODERATE RAINFALL. A 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 SHIFTS TO THE WEST COAST BY THE BEGINNING OF NEXT  
WEEK AS THE TROUGH APPROACHES THE WEST COAST. HEAVY RAINFALL  
ALONG WITH HIGHER ELEVATION SNOW WILL INCREASE ACROSS THE PACIFIC  
NORTHWEST AND INTERMOUNTAIN WEST ON SUNDAY...AND WILL CONTINUE  
INTO MONDAY WHILE SPREADING FARTHER SOUTH ACROSS CALIFORNIA. BY  
TUESDAY...MOST OF THE WEST COAST WILL DRY OUT WITH THE EXCEPTION  
OF THE NORTHERN PORTIONS OF THE PACIFIC NORTHWEST WITH YET ANOTHER  
ROUND OF RAINFALL ALONG WITH HIGHER ELEVATION SNOW. THE BULK OF  
PRECIPITATION WILL BE IN THE NORTHERN PLAINS/UPPER MIDWEST...WITH  
A MIX OF RAIN/SNOW/WINTRY PRECIPITATION WILL BE POSSIBLE.  
 
IN TERMS OF TEMPERATURES...ABOVE AVERAGE TEMPERATURES WILL BE  
PRESENT ACROSS THE CENTRAL AND WESTERN PORTIONS OF THE U.S.  
THROUGH MOST OF THE WEEKEND. IN CONTRAST...BELOW AVERAGE  
TEMPERATURES WILL BE PRESENT ACROSS THE EASTERN AND SOUTHEASTERN  
U.S. THROUGHOUT THE WEEKEND. BELOW AVERAGE TEMPERATURES WILL  
CREEP IN ACROSS THE WEST COAST BY MONDAY AND BE PRESENT INTO  
TUESDAY.  
 
REINHART  
 

 
 
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