781  
FXUS02 KWBC 240647  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
247 AM EDT TUE JUL 24 2018  
 
VALID 12Z FRI JUL 27 2018 - 12Z TUE JUL 31 2018  
   
..HEAT WAVE LINGERS OVER THE WEST
 
 
...HEAVY RAINFALL THREAT TO SPREAD FROM CENTRAL ROCKIES/PLAINS TO  
MID-SOUTH THEN AGAIN OVER THE EAST...  
   
..GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER THREATS
 
 
AMPLIFIED MID-UPPER LEVEL TROUGHING/HEIGHT FALLS WORK OVER THE  
GREAT LAKES/OH VALLEY FRI THROUGH THE NORTHEAST THIS WEEKEND. SOME  
LINGERING HEAVY RAINS FUELED BY DEEPENED MOISTURE ALONG AND AHEAD  
OF SURFACE FRONTS CAN BE EXPECTED EARLY, WITH SOME LOCAL RUNOFF  
ISSUES POSSIBLE GIVEN WET ANTECEDENT CONDITIONS. ADDITIONAL  
ACTIVITY WILL TRAIL SOUTHWARD ALONG OR OFF THE EAST COAST AND  
ACROSS FLORIDA. MEANWHILE, A HOT MID-UPPER LEVEL RIDGE OVER THE  
SOUTHWEST/WEST OFFERS A CONTINUING PATTERN WITH ABOVE NORMAL  
SUMMER HEAT. A SERIES OF ACTIVE IMPULSES WILL LINGER WITHIN  
MONSOONAL FLOW OVER THE SOUTHWEST/SRN ROCKIES AND ALSO OVERTOP THE  
UPPER RIDGE. THESE WILL DIG INTO THE CENTRAL U.S. IN A REGION OF  
FAVORABLE UPPER DIFFLUENCE AND INTERACT WITH SURFACE BOUNDARIES,  
INSTABILITY, AND FAVORABLE LOW LEVEL MOISTURE INFLOW/CONVERGENCE.  
WEEKEND MID-UPPER LEVEL TROUGH AMPLIFICATION OVER THE N-CENTRAL  
U.S. WILL DIG THROUGH THE MS VALLEY EARLY NEXT WEEK AND INDUCE AN  
ORGANIZED LOW AND GRADUAL FRONTAL SYSTEM PROGRESSION DOWNSTREAM  
ACROSS THE EAST-CENTRAL U.S. THIS PATTERN SUPPORTS MULTIPLE  
EPISODES OF HEAVY CONVECTION FROM THE CENTRAL ROCKIES/PLAINS  
THROUGH THE MID-LOWER MS/MID-SOUTH INTO THE WEEKEND WHOSE THREAT  
SPREADS/EXPANDS OVER MUCH OF THE EAST-CENTRAL U.S. TO ERN U.S.  
EARLY-MID NEXT WEEK. HEAVY RAINFALL AND REPEAT CELLS OFFER A  
WIDESPREAD EXCESSIVE RAINFALL THREAT FUELED BY AN INCREASINGLY  
DEEP LAYERED MOISTURE INFLOW PATTERN TO ALIGN ROUGHLY PARALLEL TO  
THE MAIN FRONT/ACTIVITY WEDGED BETWEEN THE UPSTREAM TROUGH ALOFT  
AND DOWNSTREAM WESTERN ATLANTIC RIDGE.  
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A  
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FROM THE  
GFS/ECMWF/UKMET AND GEFS/ECMWF ENSEMBLES IN A PATTERN WITH ABOVE  
NORMAL PREDICTABILITY.  
 
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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