163  
FXUS02 KWBC 140538  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
137 AM EDT SUN OCT 14 2018  
 
VALID 12Z WED OCT 17 2018 - 12Z SUN OCT 21 2018  
   
..PATTERN OVERVIEW
 
 
UPPER RIDGING OVER BRITISH COLUMBIA AND FLORIDA WILL FAVOR  
PROGRESSIVE TROUGHING THROUGH THE NORTHERN TIER EAST OF THE  
ROCKIES WITH A CLOSED LOW IN THE SOUTHWEST. A COUPLE CANADIAN  
FRONTS WITH LIMITED MOISTURE WILL SWING THROUGH THE GREAT  
LAKES/NORTHEAST LATER THIS WEEK INTO THE WEEKEND WITH A RENEWED  
PUSH OF COOLER AIR. FLORIDA WILL REMAIN WARM/HOT WITH SCATTERED  
SHOWERS/STORMS AND THE PACIFIC NORTHWEST SHOULD SEE ABOVE AVERAGE  
TEMPERATURES AND DRY CONDITIONS.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
A MULTI-MODEL DETERMINISTIC BLEND (GFS/ECMWF/CANADIAN) SUFFICED  
FOR THE WED-FRI PERIOD AS MODELS SHOWED GENERALLY GOOD CONSENSUS  
WITH RESPECT TO THE UPPER LOW LINGERING ACROSS THE SOUTHWEST AND  
WITH AMPLIFYING SHORTWAVE ENERGY CROSSING THE GREAT LAKES. FOR  
SAT/SUN, ONE POINT OF CONTENTION AMONG THE GUIDANCE BECOMES HOW  
MUCH EROSION/FLATTENING OF THE WESTERN NORTH AMERICAN RIDGE OCCURS  
AS SHORTWAVE ENERGY EXITS THE NORTHEASTERN PACIFIC. THE ECMWF AND  
ITS ENSEMBLES HAVE MOSTLY BEEN MORE AGGRESSIVE WITH FLATTENING THE  
RIDGE WHILE THE GFS/GEFS HAVE MAINTAINED IT, THOUGH THE LATEST  
ECMWF GUIDANCE WAS CLOSER TO THE GFS/GEFS THAN PREVIOUS CYCLES. IN  
THE EAST, GFS/CANADIAN WERE MUCH STRONGER WITH THE UPPER TROUGH  
AND SURFACE LOW EXITING THE NORTHEAST BUT A BLEND OF THE SOLUTIONS  
WITH MORE ENSEMBLE WEIGHTING PROVED TO BE A REASONABLE COMPROMISE  
FOR NOW.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
BELOW AVERAGE TEMPERATURES WILL CONTINUE LATE THIS WEEK INTO THE  
WEEKEND FOR THE SOUTHWEST THROUGH THE SOUTHERN PLAINS (ESPECIALLY  
TEXAS) NORTHEASTWARD THROUGH THE OHIO VALLEY INTO THE NORTHEAST.  
ON THE WARM SIDE OF THE STATIONARY FRONT, FLORIDA WILL SEE  
WARM/HOT TEMPERATURES THAT MAY TIE/BREAK RECORD HIGHS AT SOME  
LOCATIONS BUT THE CHANCE OF SHOWERS/STORMS WILL REMAIN FOR MUCH OF  
THE STATE.  
 
PRECIPITATION WILL BE GENERALLY LIGHT EXCEPT FOR THE TEXAS COAST  
JUST TO THE NORTHEAST OF THE LINGERING FRONT ALONG AN INVERTED  
TROUGH. THIS SIGNAL HAS BEEN STEADY FOR SEVERAL MODEL/ENSEMBLE  
CYCLES (ROUGHLY VICTORIA TO BROWNSVILLE). UPPER LOW IN THE  
SOUTHWEST WILL SUPPORT RAIN/SNOW SHOWERS FOR AT LEAST THE HIGHER  
ELEVATIONS THOUGH ITS FOCUS KEEPS SHIFTING WITH THE SMALL CHANGES  
IN THE SHAPE OF THE UPPER LOW PER THE MODELS. THE REST OF THE  
LOWER 48 WILL BE LARGELY DRY WITH SOME GENERALLY LIGHT RAIN/SNOW  
SHOWERS AROUND THE LAKES AND INTO THE NORTHEAST ALONG/AHEAD OF THE  
COLD FRONT NEXT WEEKEND.  
 
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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