582  
FXUS02 KWBC 261556  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1156 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
 
 
THE RIDGE OVER THE WESTERN U.S. WILL KEEP MUCH OF THE WEST COAST,  
SOUTHWEST AND GREAT BASIN HOT AND MOSTLY DRY. WITH THE HEAT WAVE  
PERSISTING, MANY LOCATIONS WILL LIKELY HAVE HEAT ADVISORIES AND/OR  
EXCESSIVE HEAT WARNINGS IN EFFECT. LOW HUMIDITY DURING THE  
AFTERNOON, ALONG WITH POOR RECOVERIES OVERNIGHT, CONDITIONS NEAR  
CRITICAL FIRE DANGER MAY PERSIST. ACTIVE IMPULSES LINGER IN THE  
SOUTHWEST/SOUTHERN ROCKIES AND OVER THE RIDGE AND WILL DIG INTO  
THE CENTRAL U.S. IN FAVORABLE UPPER DIFFLUENCE TO INTERACT WITH  
SURFACE BOUNDARIES, INSTABILITY, AND FAVORABLE LOW LEVEL MOISTURE  
INFLOW/CONVERGENCE. THE RIDGE OVER THE ATLANTIC OCEAN WILL  
RETROGRADE BACK TOWARD THE GULF STREAM, WHICH WILL RESULT IN THE  
TROUGH SANDWICHED OVER THE CENTRAL U.S. TO DIG FURTHER SOUTH WITH  
LITTLE EASTWARD PROGRESSION. OTHERWISE, A WEAK LONGWAVE TROUGH  
OFFSHORE THE PACIFIC NORTHWEST EARLY NEXT WEEK GRADUALLY EJECTS  
INLAND TO MODERATE FLOW.  
 
AS THE TROUGH DIGS THROUGH THE MISSISSIPPI VALLEY EARLY NEXT WEEK  
FRONTAL LOWS WILL DEVELOP WITH GRADUAL FRONTAL SYSTEM PROGRESSIONS  
DOWNSTREAM OVER THE E-CENTRAL U.S. EXPECT MULTIPLE EPISODES OF  
HEAVY CONVECTION FROM THE CENTRAL ROCKIES/PLAINS THROUGH THE  
MID-LOWER MISSISSIPPI VALLEY/MID-SOUTH THIS WEEKEND WHOSE THREAT  
SPREADS OVER MUCH OF THE EAST-CENTRAL TO SOUTHEAST/EASTERN U.S.  
NEXT WEEK. SLOW BANDS OF HEAVY RAINFALL TRACKING OVER THE SAME  
AREA WILL KEEP THREAT FOR WIDESPREAD EXCESSIVE RAINFALL ELEVATED  
IN THE EXTENDED PERIODS.  
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS DERIVED FROM A BLEND OF THE  
00 UTC ECMWF/GFS, 06 UTC GFS AND THE 00 UTC NAEFS/GEFS/ECMWF  
ENSEMBLES. THE ECMWF CONTINUE TO BE MORE AMPLIFIED THAN ITS  
COUNTERPARTS AND MAINTAINED A SLIGHTLY HIGH WEIGHTING THAN THE  
00/06 UTC RUNS OF THE GFS. WEIGHTING OF THE ENSEMBLE MEANS  
INCREASE INCREMENTALLY THROUGH THE END OF THE EXTENDED PERIOD.  
 
CAMPBELL  
 
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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