089  
FXUS02 KWBC 190651  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 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
 
 
MULTI-MODEL BLEND PROVED TO BE A GOOD STARTING POINT FOR THU/FRI  
AS THE NORTHEASTERN TROUGH EXITS AND THE WESTERN TROUGH PLOWS  
EASTWARD. DIFFERENCES START TO EXPAND IN THE SOUTHEAST BY SATURDAY  
AS LOW PRESSURE ORGANIZES IN THE NORTHEASTERN GULF OF MEXICO AND  
LIFTS NORTHEASTWARD ALONG THE COAST. THE ECMWF AND MOST OF ITS AND  
THE GEFS' ENSEMBLES WERE GENERALLY A BIT WEST OF RECENT GFS RUNS  
EXCEPT FOR PERHAPS THE FV3 (WHICH WAS A BIT QUICKER). GIVEN THE  
TREND TOWARD MORE AMPLIFICATION IN THE MEDIUM RANGE VS EARLIER  
FORECASTS, PREFERRED THE MORE ROBUST/WEST SOLUTIONS NEAR THE 12Z  
ECMWF/CANADIAN WHICH WILL TAKE THE LOW UP THE COAST TO ABOUT THE  
MID-ATLANTIC BEFORE TURNING EASTWARD IN RESPONSE TO INCREASED  
RIDGING TO ITS NORTHEAST. UPSTREAM, PAIR OF FRONTS WILL CONVERGE  
AND SLOW INTO 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. GAVE MUCH MORE WEIGHT TO THE 12Z  
ECMWF ENSEMBLE MEAN BY NEXT SUN/MON WHICH WAS MORE AMPLIFIED THAN  
THE GEFS MEAN.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THANKSGIVING SUMMARY (THU 11/22) - COLD TURKEY, INDEED. RECORD  
COLD WILL LIKELY BE AN UNWELCOME THANKSGIVING GUEST FOR MANY IN  
THE NORTHEAST, WITH HIGH TEMPERATURES 15 TO NEAR 30 DEG F BELOW  
AVERAGE AND MANY AREAS STAYING WELL BELOW FREEZING, WHILE LOW  
TEMPERATURES MAY REACH THE SINGLE DIGITS ON EITHER SIDE OF ZERO.  
WET ALONG THE WEST COAST INTO THE GREAT BASIN AND ROCKIES WITH  
NEAR AVERAGE TEMPERATURES AND HIGHER ELEVATION SNOW. MILDER AND  
DRY FOR THE HIGH PLAINS WITH 40S/50S COMMON. RAIN CHANCE FOR THE  
GULF COAST FROM TEXAS EASTWARD THROUGH MUCH OF FLORIDA TO THE  
NORTH OF A FRONT IN THE FLORIDA STRAITS AND SURFACE LOW SOUTH OF  
HOUSTON.  
 
THE ENTIRE WEST COAST AND MUCH OF THE INTERIOR WILL SEE WIDESPREAD  
RAIN/ELEVATION SNOW TO START THE PERIOD WEDNESDAY. MULTI-DAY  
RAINFALL AMOUNTS MAY BE IN THE 3-6 INCH RANGE OVER FAVORED AREAS  
AND 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.  
A POTENTIAL LOW PRESSURE SYSTEM MOVING FROM THE GULF AND ACROSS  
THE SOUTHEAST NEXT WEEKEND WOULD SUPPORT THE POTENTIAL FOR HEAVY  
PRECIPITATION ACROSS PORTIONS OF THE SOUTHEAST, MID-ATLANTIC, AND  
SOUTHERN/CENTRAL APPALACHIANS. THIS MAY COINCIDE WITH ANOTHER VERY  
BUSY TRAVEL DAY ON SUNDAY.  
 
MUCH BELOW AVERAGE TEMPERATURES IN THE NORTHEAST WILL SLOWLY EASE  
BACK TOWARD TYPICAL LATE NOVEMBER VALUES BY THE WEEKEND (AND  
LIKELY ABOVE AVERAGE MIN TEMPERATURES). TEMPERATURES IN THE WEST  
WILL BE NEAR TO ABOVE AVERAGE FOR OVERNIGHT LOWS BUT NEAR TO BELOW  
AVERAGE FOR AFTERNOON HIGHS THANKS TO AN ABUNDANCE OF CLOUD COVER.  
THAT WILL TREND BACK TO NEAR AVERAGE BY THE END OF THE PERIOD. THE  
PLAINS AND UPPER MIDWEST WILL SEE MILDER TEMPERATURES  
THURSDAY-SATURDAY, GENERALLY ABOVE FREEZING FOR AFTERNOON HIGHS,  
BUT THEN COLDER AIR WILL LIKELY MOVE IN BEHIND A FRONT THIS  
WEEKEND.  
 
RYAN/FRACASSO  
 
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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