330  
FXUS02 KWBC 080701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EST THU NOV 08 2018  
 
VALID 12Z SUN NOV 11 2018 - 12Z THU NOV 15 2018  
 
...GREAT LAKES/OH VALLEY/APPALACHIANS TO INTERIOR NORTHEAST EARLY  
SEASON SNOW THREAT...  
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
GFS/ECMWF AND GEFS/ECMWF ENSEMBLE SOLUTIONS ARE WELL CLUSTERED  
INTO EARLY NEXT WEEK, BUT BECOME INCREASING VARIED WITH SMALLER  
SCALE SYSTEM DETAILS INTO NEXT MID-LATE WEEK WHEN A COMPOSITE  
BLEND OF ENSEMBLE MEANS IS PREFERRED. THIS SOLUTION MAINTAINS GOOD  
WPC CONTINUITY.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A STORM TRACK TO THE NORTHEAST PACIFIC/GULF OF ALASKA MAINTAINS AN  
AMPLIFIED RIDGE AXIS ALOFT ALONG/OFFSHORE WESTERN NORTH AMERICA  
INTO EARLY NEXT WEEK. DOWNSTREAM CLIPPER LOW TRACK AND FAVORABLE  
DYNAMICS WILL SQUEEZE OUT A SWATH OF SNOW IN COOLED AIR OF THE  
GREAT LAKES/NORTHEAST. MEANWHILE, POTENT WEEKEND SHORTWAVE DIGGING  
THROUGH THE INTERMOUNTAIN WEST/ROCKIES WILL FAVOR A LEAD SNOW  
BURST OVER THE SOUTH-CENTRAL ROCKIES SUNDAY TO SPILL INTO THE  
PLAINS AS AIDED BY COLD POST-FRONTAL UPSLOPE FLOW.  
 
THE UPPER TROUGH WILL AMPLIFY OVER THE CENTRAL U.S. EARLY NEXT  
WEEK WITH INCREASING NORTHERN AND SOUTHERN STREAM PHASING TO THE  
LEE OF THE AMPLIFIED BUT GRADUALLY INLAND SHIFTING UPSTREAM RIDGE.  
LEAD WAVE/FRONTAL GENESIS AND DEEP MOISTURE RETURN WILL FUEL HEAVY  
RAIN/CONVECTION EXPANSION NORTHWARD ACROSS THE EAST-CENTRAL THEN  
EASTERN U.S. MOISTURE FEEDING BACK INTO A SHARPENING BAROCLINIC  
ZONE MEANWHILE PRESENTS AN ORGANIZED SNOW THREAT THROUGH THE  
APPALACHIANS/OHIO VALLEY, WITH AMPLE LAKE EFFECT ENHANCEMENT LEE  
OF THE GREAT LAKES. THERE IS CONTINUED UNCERTAINTY WITH RESPECT TO  
THE LEAD COASTAL/INLAND LOW TRACK AND WESTERN EXTENT OF THE MAIN  
PRECIPITION SHIELD/COLD AIR WITH RECENT ECMWF RUNS OFFERING A MORE  
INLAND TRACK THAN MORE COASTAL TRACKS FROM RECENT GFS RUNS. A  
LARGER PERCENTAGE OF GEFS AND ECMWF ENSEMBLE MEMBERS FAVOR THE  
COASTAL SOLUTION BUT THE MINORITY SUBSET OF MORE INLAND SOLUTIONS  
CANNOT BE RULES OUT CONSIDERING THE AMPLITUDE AND WESTWARD  
POSITION OF THE MAIN MID-UPPER LEVEL TROUGH. ENSEMBLE MEANS OFFER  
A DECENT COMPROMISE AT THIS POINT. OVERALL, THERE IS A THREAT FOR  
HEAVY GREAT LAKES/OH VALLEY/APPALACHIANS TO INTERIOR NORTHEAST  
EARLY SEASON SNOWS.  
 
WELL UPSTREAM, PACIFIC TROUGH ENERGY AND HEIGHT FALLS START TO  
WORK INTO THE NORTHWEST EARLY-MID NEXT WEEK AS THE LEAD/AMPLIFIED  
RIDGE ALOFT GRADUALLY/FINALLY SHIFTS INLAND. THIS SUPPORTS AN  
INCREASED CHANCE FOR PRECIPITATION INCLUDING MODEST ELEVATION  
SNOWS.  
 
SCHICHTEL  
 
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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