188  
FXUS02 KWBC 261319  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
818 AM EST SUN NOV 26 2017  
 
VALID 12Z WED NOV 29 2017 - 12Z SUN DEC 03 2017  
 
OVERVIEW/GUIDANCE EVALUATION  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
THE GUIDANCE SHOWS VERY GOOD AGREEMENT WITH THE PROGRESSION OF  
SYSTEMS THIS PERIOD. SOME SLOWING IS NOTED BY LATE NEXT WEEKEND  
AS TROUGHS ALOFT GAINS SOME AMPLITUDE ACROSS ATLANTIC CANADA AND  
THE WEST. THE PRESSURES, WINDS, 500 HPA HEIGHTS, AND FRONTS USED  
A BLEND OF THE 00Z CANADIAN, 00Z UKMET, 06Z GFS, AND 00Z ECMWF  
THROUGH MUCH OF THE PERIOD, WITH SOME ADDITION OF 00Z ECMWF AND  
00Z NAEFS ENSEMBLE MEANS NEXT WEEKEND TO ACCOUNT FOR UNCERTAINTY.  
THIS LED TO REASONABLE CONTINUITY. THE TEMPERATURES, DEW POINTS,  
CLOUDS, WEATHER TYPE, AND RAIN CHANCES ARE A FAIRLY EVEN BLEND OF  
THE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE TO BETTER ACCOUNT FOR  
UNCERTAINTY. WILL AWAIT THE 12Z GFS BEFORE MAKING ANY  
DETERMINATION ON QPF DUE TO THE SPREAD SEEN WITH THE EASTERN  
SYSTEM.  
 
WEATHER HIGHLIGHTS  
~~~~~~~~~~~~~~~~~~  
THE WEST WILL SEE A GRADUAL INCREASE IN MOISTURE WITH TIME AS  
UPPER TROUGHING APPROACHES/ARRIVES. UPPER TROUGHING WILL SUPPORT A  
TREND TOWARD BELOW NORMAL TEMPS OVER AN INCREASING PORTION OF THE  
WEST NEXT WEEKEND. MOISTURE WILL REACH THE NORTHWEST AROUND LATE  
WEEK WITH OTHER PARTS OF THE WEST STARTING TO SEE AREAS OF PRECIP  
DURING THE WEEKEND. THE PACIFIC NORTHWEST/NORTHERN ROCKIES WILL  
BE ONE FAVORED AREA OF FOCUS. THE AREA ENCOMPASSING  
CENTRAL-SOUTHERN CALIFORNIA NORTHEASTWARD INTO THE ROCKIES MAY BE  
ANOTHER REGION WITH SOME LOCALLY ENHANCED TOTALS DEPENDING ON  
DETAILS OF THE UPPER TROUGH AND LINGERING SOUTHERN STREAM ENERGY  
EJECTING AHEAD OF THE TROUGH.  
 
EXPECT THE NORTHERN PLAINS AND VICINITY TO SEE THE MOST CONSISTENT  
WARMTH DURING THE PERIOD WITH TEMPS AVERAGING 10-15F ABOVE NORMAL.  
SOME OF THIS WARMTH WILL EXTEND INTO THE CENTRAL HIGH PLAINS DAY  
3 WED, AND PATTERN EVOLUTION BY NEXT WEEKEND SHOULD SUPPORT A  
BROADER AREA OF PLUS 10F OR GREATER ANOMALIES OVER THE CENTRAL  
U.S..  
 
THE LEADING IMPULSE OVER THE SOUTH-CENTRAL PLAINS/MS VALLEY MAY  
PRODUCE A LOCALIZED AREA OF ENHANCED RAINFALL AROUND MID-WEEK  
BEFORE WEAKENING. THE TRAILING WESTERN U.S. SHORTWAVE SHOULD  
PRODUCE SOME LIGHT RAIN/HIGH ELEVATION SNOW OVER/NEAR THE  
NORTHERN/CENTRAL ROCKIES WED AND THEN PROMOTE A GENERAL INCREASE  
IN COVERAGE OF PRECIP OVER THE EAST BY THURSDAY AND FRIDAY.  
HOWEVER, SOME GUIDANCE SPREAD LEADS TO UNCERTAINTY IN EXACT TIMING  
AND PRECIPITATION TYPE. IF ANY HEAVIER PRECIP OCCURS, IT IS MOST  
LIKELY FROM THE MID ATLANTIC INTO THE NORTHEAST, BUT NOTE THAT A  
FAIRLY PROGRESSIVE/LIGHT EPISODE OF PRECIP IS ALSO A POSSIBLE  
SCENARIO. THERE IS THE POTENTIAL FOR A PERIOD OF BREEZY TO WINDY  
CONDITIONS. THE SYSTEM CROSSING THE EAST WILL BRING A COOLING  
TREND TO THAT PART OF THE COUNTRY FOR THE LATE WEEK/WEEKEND TIME  
FRAME.  
 
ROTH/RAUSCH  

 
 
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