232  
FXUS02 KWBC 211601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT THU JUN 21 2018  
 
VALID 12Z SUN JUN 24 2018 - 12Z THU JUN 28 2018  
   
..NORTH-CENTRAL U.S. HEAVY CONVECTIVE RAINFALL PATTERN
 
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENTS WITH WEATHER HIGHLIGHTS
 
 
MODELS AND ENSEMBLES CONTINUE TO SHOW EXCELLENT AGREEMENT THAT A  
SPLIT FLOW UPPER-LEVEL PATTERN ACROSS NORTH AMERICA WILL GRADUALLY  
BECOME MORE CONSOLIDATED BY THE MIDDLE OF NEXT WEEK AS HEIGHTS ARE  
FORECAST TO INCREASE OVER THE CENTRAL AND EASTERN U.S. UNTIL  
THEN, A COUPLE OF UPPER-LEVEL SHORTWAVES ARE EXPECTED TO TRACK  
GENERALLY FROM THE NORTHERN ROCKIES ACROSS THE CENTRAL PLAINS AND  
THEN LIFTS OUT INTO THE GREAT LAKES. THIS MODESTLY PROGRESSIVE  
PATTERN APPEARS TO SUPPORT THE AMPLIFICATION OF MESOSCALE  
CONVECTIVE SYSTEMS OVER THE CENTRAL PLAINS EARLY NEXT WEEK WHERE  
LOCALLY EXCESSIVE RAINFALL IS POSSIBLE. BY THE MIDDLE OF NEXT  
WEEK, MODELS AGREE THAT THE MAIN ENERGY ASSOCIATED WITH THE  
SHORTWAVES WILL WEAKEN AND LIFTS TOWARD THE GREAT LAKES AS A  
PACIFIC FRONT DIPS INTO THE NORTHERN PLAINS. SOME REMNANT  
THUNDERSTORMS SHOULD PUSH INTO THE OHIO VALLEY INTO THE  
APPALACHIANS BY THE MIDDLE OF NEXT WEEK. OVER THE SOUTHEASTERN  
U.S., A WEAKENING FRONT SHOULD PROMOTE SHOWERS AND THUNDERSTORMS  
FROM FLORIDA WESTWARD INTO THE CENTRAL GULF COAST. MEANWHILE, THE  
GFS HAS BEGUN TO INDICATE THE POSSIBILITY OF A SURFACE LOW  
LINGERING JUST OFF THE CAROLINA COAST ALONG THE DYING FRONT TOWARD  
THE MIDDLE OF NEXT WEEK.  
 
ACCORDINGLY, THE WPC MEDIUM RANGE MORNING PRODUCT SUITE WAS  
DERIVED FROM A COMPOSITE BLEND OF THE 00Z ECMWF AND 06Z GFS  
TRENDING TOWARD THEIR ENSEMBLE MEANS THROUGH DAY 7. THIS  
MAINTAINS EXCELLENT WPC CONTINUITY.  
 
KONG  
 
WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS, SURFACE SYSTEMS,  
WEATHER GRIDS, QUANTITATIVE PRECIPITATION, AND WINTER WEATHER  
OUTLOOK PROBABILITIES ARE FOUND AT:  
 
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
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