786  
FXUS02 KWBC 031558  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1157 AM EDT SAT NOV 03 2018  
 
VALID 12Z TUE NOV 06 2018 - 12Z SAT NOV 10 2018  
   
..OVERVIEW
 
 
BROAD CYCLONIC FLOW WILL REMAIN ANCHORED OVER MOST OF THE LOWER 48  
NEXT WEEK AS EMBEDDED SYSTEMS PASS THROUGH THE TROUGH. A LEAD  
SYSTEM ON TUESDAY WILL EXIT THROUGH THE CENTRAL GREAT LAKES WHILE  
ANOTHER WILL DIVE THROUGH THE WEST AND SPIN UP LATE THURSDAY INTO  
FRIDAY THROUGH THE EASTERN GREAT LAKES. THIS MAY SPREAD SOME  
WINTRY WEATHER ACROSS THE CENTRAL PLAINS AND TO THE NORTH OF THE  
SURFACE LOW TRACK.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
A MULTI-MODEL BLEND OFFERED A REASONABLE STARTING POINT FOR THE  
LEAD SYSTEM IN THE EAST TUE/WED AS THE COLD FRONT PUSHES OFFSHORE.  
BY NEXT THURSDAY, THE MODELS AND ENSEMBLES HAVE NOW SHOWN FOR TWO  
CONSECUTIVE RUNS (BUT MUCH UNLIKE 24 HRS AGO) A STRONGER NORTHERN  
STREAM SHORTWAVE THROUGH THE WEST ON WEDNESDAY THAT WILL LIKELY  
AMPLIFY INTO THE PLAINS THURSDAY AND SPIN UP A SURFACE LOW OVER  
THE LOWER MISSISSIPPI VALLEY THAT WILL LIFT NORTHEASTWARD FRIDAY  
AND OUT THROUGH THE ST. LAWRENCE VALLEY SATURDAY. THIS WAS A  
SIGNIFICANT CHANGE FROM THE 00Z/02 ENSEMBLES AS ONLY A FEW MEMBERS  
SHOWED SUCH A SOLUTION BUT THE CONSENSUS IS STRONG IN THE 00Z/03  
ENSEMBLES. HOWEVER, TIMING/AMPLITUDE DIFFERENCES ARE EVIDENT WITH  
THE 00Z/06Z GFS QUICKER/WEAKER AND THE 00Z ECMWF SLOWER/STRONGER.  
THEIR RESPECTIVE ENSEMBLE MEANS WERE A BIT SLOWER/QUICKER THAN  
THEIR DETERMINISTIC COUNTERPARTS, RESPECTIVELY, TO OFFER A BIT  
BETTER AGREEMENT. THE 00Z PARALLEL GFS (FV3-GFS) WAS CLOSE TO THE  
PREFERRED SPEED NEAR THE ENSEMBLES AS WAS THE 00Z CANADIAN TO A  
LESSER DEGREE.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
DYNAMIC SYSTEM IN THE EAST ON TUESDAY WILL SPREAD RAIN/STORMS  
(POSSIBLY SEVERE ALONG THE I-81 TO I-95 CORRIDOR BETWEEN GEORGIA  
AND PENNSYLVANIA) THROUGH THE EAST WITH ANOTHER SHOT OF COOLER AIR  
BEHIND IT THROUGH THE HIGH PLAINS. LATER WEEK MORE MODEST  
PRECIPITATION MAY RENEW OVER THE SOUTHERN PLAINS AS THE WESTERN  
SHORTWAVE TAPS AVAILABLE WESTERN GULF OF MEXICO MOISTURE ATOP A  
STATIONARY BOUNDARY. WITH MARGINALLY COLD AIR TO THE NORTH, WINTRY  
PRECIPITATION IS POSSIBLE ALONG AND EAST OF THE CENTRAL ROCKIES  
THROUGH THE CENTRAL PLAINS. ISOLATED BUT POTENTIALLY HEAVIER RAINS  
IN THE WARM SECTOR MAY SPREAD NORTHEASTWARD OUT OF THE LOWER  
MISSISSIPPI VALLEY FRIDAY INTO THE NORTHEAST AND CENTRAL  
APPALACHIANS AS THE SURFACE LOW DEEPENS AND HEADS TOWARD THE  
EASTERN GREAT LAKES. NORTHWEST FLOW AROUND THE WESTERN GREAT LAKES  
MAY SUPPORT ON AND OFF LAKE EFFECT SNOWS WITH COLD AIR ALOFT AND  
STILL MILD LAKE TEMPERATURES.  
 
TEMPERATURES WILL BE BELOW AVERAGE FROM THE NORTHERN ROCKIES  
THROUGH THE PLAINS INTO THE GREAT LAKES AND OHIO VALLEY AS  
REINFORCING COLD FRONTS DRAG COOL/COLD CANADIAN AIR THROUGH THE  
REGION. THE WEST WILL SEE NEAR TO ABOVE AVERAGE TEMPERATURES  
THANKS TO UPPER RIDGING WHILE THE EAST WILL BE A BIT VARIABLE --  
WARMING UP AHEAD OF THE GREAT LAKES SYSTEM TUE/WED THEN COOLING  
OFF AFTER THE FRONT PASSES.  
 
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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