899  
FXUS02 KWBC 191607  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1106 AM EST MON NOV 19 2018  
 
VALID 12Z THU NOV 22 2018 - 12Z MON NOV 26 2018  
 
...RECORD COLD TEMPERATURES ON THANKSGIVING/BLACK FRIDAY FOR MUCH  
OF THE NORTHEAST/NEW ENGLAND...  
 
...COULD BE THE COLDEST THANKSGIVING SINCE 1996 FOR THE  
DC-PHL-NYC-BOS CORRIDOR...  
 
   
..OVERVIEW
 
 
VERY COLD BUT MOSTLY DRY IN MUCH OF THE EAST WHILE IT WILL BE  
STORMY IN THE WESTERN US LATER THIS WEEK. A COUPLE OF COLD FRONTS  
WILL PUSH ACROSS THE LOWER 48 AND POTENTIALLY LIFT UP ALONG THE  
EAST COAST SAT/SUN DURING A VERY BUSY TRAVEL TIME. ABOVE AVERAGE  
TEMPERATURES IN THE HIGH PLAINS WILL TREND BACK TO BELOW AVERAGE  
BY NEXT WEEK.  
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MODEL GUIDANCE SUGGEST A SPLIT FLOW PATTERN THROUGH MUCH OF  
EXTENDED PERIODS, WITH THE SOUTHERN STREAM BECOMING MORE DOMINANT  
THIS WEEKEND. MODEL DIFFERENCES ARE APPARENT AFTER DAY 3  
(THANKSGIVING) AND CONTINUE TO INCREASE THROUGH THE END OF THE  
FORECAST. THE LAST TWO RUNS OF THE GFS CONTINUE TO BE FASTER WHILE  
THE ECWMF, CANADIAN, UKMET AND ENSEMBLE MEANS MAINTAIN A  
SLOWER/WEST SOLUTION. CHOSE TO MAINTAIN CONTINUITY BY USING A  
MULTI-MODEL BLEND, USING THE GFS VERY SPARINGLY.  
 
GUIDANCE CONTINUES TO DEPICT A PAIR OF FRONTS CONVERGING/SLOWING  
OVER THE MID-MISSISSIPPI AND WESTERN OHIO VALLEYS AS THE UPPER  
TROUGH SHARPENS. THIS MAY TAKE ANOTHER AREA OF LOW PRESSURE  
NORTHEASTWARD BUT ON THE WEST SIDE OF THE APPALACHIANS NEXT  
SUN/MON. AGAIN PREFERRED THE SLOWER/SHARPER SOLUTIONS UNLIKE THE  
RECENT QUICKER/WEAKER GFS RUNS.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A RATHER CHILLY THANKSGIVING DAY IS IN STORE FOR MUCH OF THE  
NORTHEAST, LOWER GREAT LAKES AND NORTHERN MID-ATLANTIC REGIONS  
WHERE AFTERNOON HIGHS WILL HOVER NEAR 15 TO 30 DEG F BELOW  
AVERAGE. THE MAJORITY OF AREA WILL STAY WELL BELOW FREEZING, WHILE  
LOW TEMPERATURES MAY REACH THE SINGLE DIGITS ON EITHER SIDE OF  
ZERO. THE MUCH BELOW AVERAGE TEMPERATURES IN THE NORTHEAST WILL  
SLOWLY EASE BACK TOWARD TYPICAL LATE NOVEMBER VALUES BY THE  
WEEKEND (AND LIKELY ABOVE AVERAGE MINIMUM TEMPERATURES).  
 
THE ENTIRE WEST COAST AND MUCH OF THE INTERIOR WEST WILL BE IN A  
PROLONGED ACTIVE, WET PATTERN. WITH EXTENSIVE CLOUD COVER  
EXPECTED, OVERNIGHT TEMPERATURES ARE FORECAST TO BE NEAR OR ABOVE  
AVERAGE THROUGH THE EXTENDED PERIODS. WIDESPREAD RAIN/ELEVATION  
SNOW WILL LIKELY RESULT IN MULTI-DAY TOTALS OF 3-6 INCHES,  
ESPECIALLY OVER THE FAVORED UPSLOPE AREAS- EVEN ABOUT AN INCH TO  
AN INCH AND A HALF IN THE CENTRAL VALLEY. SNOW LEVELS WILL WAVER  
BUT GENERALLY FALL THROUGH THE PERIOD WITH SEVERAL FEET OF SNOW  
LIKELY AT THE HIGHEST ELEVATIONS. ACROSS THE HIGH PLAINS, THIS  
NEXT WEEK WILL GENERALLY BE MILD AND DRY WITH TEMPERATURES MAINLY  
IN THE 40S AND 50S, COOLING TO THE 30S AND 40S DURING THE WEEKEND.  
THE COOLER TEMPERATURES WILL REACH THE CENTRAL PLAINS/MIDWEST BY  
THE WEEKEND AS A COLD FRONT PASSES THROUGH.  
 
THE GULF COAST HAS AN INCREASING CHANCE FOR RAIN AS A LOW PRESSURE  
SYSTEM DEVELOPS AND TRACKS EAST ACROSS THE SOUTH AND SOUTHEAST,  
WHICH MAY SUPPORT THE POTENTIAL FOR HEAVY PRECIPITATION ACROSS  
PORTIONS OF THE SOUTHEAST, MID-ATLANTIC, AND SOUTHERN/CENTRAL  
APPALACHIANS AS THE SYSTEM TRANSITIONS TO A NOR'ESTER. THIS MAY  
COINCIDE WITH ANOTHER VERY BUSY TRAVEL DAY ON SUNDAY.  
 
CAMPBELL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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