408  
FXUS02 KWBC 260412  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1211 AM EDT THU JUL 26 2018  
 
VALID 12Z SUN JUL 29 2018 - 12Z THU AUG 02 2018  
   
..HEAT WAVE LINGERS OVER THE WEST
 
 
...HEAVY RAINFALL THREAT TO SPREAD FROM THE CENTRAL PLAINS TO  
MID-SOUTH THEN THE SOUTHEAST/EASTERN U.S...  
   
..PATTERN OVERVIEW AND WEATHER HIGHLIGHTS/THREATS
 
 
POTENT MID-UPPER LEVEL RIDGES CENTER OVER THE SOUTHWEST AND  
WESTERN ATLANTIC, WITH THE LATTER RETROGRADING BACK TOWARD THE  
GULF STREAM. SANDWICHED IN BETWEEN THIS PAIR OF 2 SIGMA POSITIVE  
HEIGHT ANOMALIES WILL BE ANOTHER WET CUT-OFF LOW MEANDERING ABOUT  
THE MID-MS VALLEY/MID-SOUTH EARLY TO MID NEXT WEEK. OTHERWISE, A  
WEAK LONGWAVE TROUGH OFFSHORE THE PACIFIC NORTHWEST EARLY NEXT  
WEEK GRADUALLY EJECTS INLAND TO MODERATE FLOW.  
 
ACTIVE IMPULSES LINGER IN THE SOUTHWEST/SRN ROCKIES AND OVER THE  
RIDGE. THESE DIG INTO THE CENTRAL U.S. IN FAVORABLE UPPER  
DIFFLUENCE TO 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 FRONTAL LOWS AND  
GRADUAL FRONAL SYSTEM PROGRESSIONS DOWNSTREAM OVER THE E-CENTRAL  
U.S. EXPECT MULTIPLE EPISODES OF HEAVY CONVECTION FROM THE CENTRAL  
ROCKIES/PLAINS THROUGH THE MID-LOWER MS/MID-SOUTH THIS WEEKEND  
WHOSE THREAT SPREADS OVER MUCH OF THE E-CENTRAL TO SOUTHEAST/ERN  
U.S. NEXT WEEK. HEAVY RAINFALL WITH 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 AS STORMS CHANNEL BETWEEN THE SLOW TO TRANSLATE  
UPSTREAM TROUGH ALOFT AND A DOWNSTREAM WESTERN ATLANTIC RIDGE.  
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A  
COMPOSITE BLEND OF THE 12 UTC ECMWF AND 18 UTC GEFS/12 UTC ECMWF  
ENSEMBLES IN A PATTERN WITH AVERAGE TO BELOW NORMAL FORECAST  
SPREAD/UNCERTAINTY. THE ECMWF IS ON THE AMPLIFIED SIDE OF THE FULL  
ENVELOPE OF SOLUTIONS AND THAT TREND SEEMS REASONABLE GIVEN  
OVERALL ANOMALOUS FLOW CHARACTERISTICS AND RECENT FLOW HISTORY.  
THIS SOLUTION MAINTAINS VERY NICE WPC CONTINUITY.  
 
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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