300  
FXUS02 KWBC 230501  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
101 AM EDT MON JUL 23 2018  
 
VALID 12Z THU JUL 26 2018 - 12Z MON JUL 30 2018  
   
..SOUTHWEST/WEST HEAT WAVE LINGERS INTO LATE WEEK
 
 
...HEAVY RAINFALL THREAT SHIFTS TO THE CENTRAL ROCKIES/PLAINS THEN  
MID-MS VALLEY/MID-SOUTH...  
   
..GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER THREATS
 
 
AMPLIFIED MID-UPPER LEVEL TROUGHING/HEIGHT FALLS WORK OVER THE  
GREAT LAKES/MIDWEST AND NORTHEAST LATER WEEK INTO THIS WEEKEND.  
EXPECT SOME PERIODS OF HEAVY CONVECTIVE RAINFALL WITH LOCAL RUNOFF  
ISSUES WITH PASSAGE OF LEAD MOISTURE POOLING FRONTAL SYSTEMS.  
ADDITIONAL ACTIVITY WILL TRAIL SOUTHWARD ALONG/OFF THE EAST COAST  
TO FL. DEEPENED MOISTURE MMAY ALLOW SOME RECORD HIGH MINIMUM  
TEMPERATURES OVER NEW ENGLAND.  
 
MEANWHILE, A HOT MID-UPPER LEVEL RIDGE OVER THE SOUTHWEST AND  
SPREAD UP OVER THE WEST AND POTENTIAL FOR RECORD MAXIMUM  
TEMPERATURES WILL EASE LATER THIS WEEK, BUT MONSOONAL MOISTURE  
COULD ALLOW FOR MORE RECORD HIGH MINIMUM TEMPERATURES. A SERIES OF  
IMPULSES ROTATING WITHIN AND ON THE PERIPHERY OF THE RIDGE DIG  
SOUTHEASTWARD INTO THE CENTRAL STATES TO INTERACT WITH SURFACE  
BOUNDARIES/INSTABILITY AND FAVORABLE LOWER LEVEL MOISTURE  
INFLOW/CONVERGENCE. FORECAST SPREAD INCREASES WITH POTENTIAL  
STREAM INTERACTIONS/WAVE GENESIS WITH MID-UPPER LEVEL TROUGH  
REDEVELOPMENT FROM THE N-CENTRAL U.S. THROUGH THE MS VALLEY DAYS  
6/7. RECENT GFS RUNS HAVE TRENDED TOWARD A BIT LESS AMPLIFIED/MORE  
PROGRESSIVE SOLUTION WITH THIS FEATURE. THE SW/WRN U.S. RIDGE  
POSITION, RECENT ERN U.S. SYSTEM HISTORY, CONTINUITY AND A  
MAJORITY GEFS/ECMWF ENSEMBLES SHOW BETTER SUPPORT FOR A SOLUTION  
MORE IN LINE WITH A MORE AMPLIFIED ECMWF. OVERALL, THIS PATTERN  
SUPPORTS MULTIPLE EPISODES OF HEAVY CONVECTION FROM THE CENTRAL  
ROCKIES/PLAINS TO THE MID-MS VALLEY AND MID-SOUTH. CONVECTIVE  
COMPLEXES/REPEAT CELLS WILL LEAD TO LOCALLY EXCESSIVE RAINFALL  
THREATS.  
 
OVERALL, THE WPC MEDIUM RANGE FORECAST SUITE WAS DERIVED FROM  
REASONABLY WELL CLUSTERED GUIDANCE FROM THE GFS/ECMWF/UKMET  
THU-SAT. OPTED TO BLEND THE WELL CLUSTERED ECMWF AND GEFS/ECMWF  
ENSEMBLE MEANS DAYS 6/7.  
 
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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