251  
FXUS02 KWBC 220329  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1128 PM EDT SAT JUL 21 2018  
 
VALID 12Z WED JUL 25 2018 - 12Z SUN JUL 29 2018  
   
..HEAVY RAIN AND FLOODING FOR THE EAST
 
   
..SOUTHWEST/WEST HEAT WAVE INTO MID-LATE WEEK
 
   
..CENTRAL ROCKIES/PLAINS TO MID-MS VALLEY HEAVY CONVECTION
 
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER THREATS
 
 
IT REMAINS THE CASE THAT FORECAST PREDICTABILITY REMAINS MUCH  
ABOVE NORMAL IN SHOWING AN AMPLIFIED MID-UPPPER LEVEL TROUGH  
LINGERING WITH AN AXIS ROUGHLY ALONG 85W INTO MIDWEEK. DEEP  
MOISTURE WITH POOLED PRECIPITABLE WATER VALUES UPWARDS OF 2"  
FEEDING INTO/AHEAD OF THE SYSTEM AND ASSOCIATED/SLOW MOVING  
SURFACE FRONTS/INSTABILITY WILL PROLONG A PATTERN FAVORABLE FOR  
CELL TRAINING/REPEAT ACTIVITY THAT WILL CONTINUE A THREAT OF  
LOCALLY HEAVY/EXCESSIVE RAINFALL FOR THE EASTERN SEABOARD. THIS  
SYSTEM WILL BE SURPLANTED BY A WELL DEFINED UPSTREAM TROUGH/HEIGHT  
FALLS WORKING ACROSS THE GREAT LAKES/MIDWEST AND NORTHEASTERN U.S.  
MID-LATE WEEK WHOSE DEVELOPMENT WILL FOCUS LINGERING HEAVY  
RAINFALL OVER THE NORTHEAST/COASTAL MID-ATLANTIC AND TRAILING TO  
FL/VICINITY CONSISTENT WITH DYNAMIC SUPPORT/FRONTAL PROGRESSIONS.  
FLASH FLOODING AND LONGER TERM/LARGER SCALE FLOODING REMAINS  
POSSIBLE IN THE WAKE OF RECENT RAINS.  
 
A HOT MID-UPPER LEVEL RIDGE MEANWHILE SETTLED OVER THE SOUTHWEST  
AND UP OVER THE WEST ALONG WITH POTENTIAL FOR RECORD MAXIMUM  
TEMPERATURES WILL GRADUALLY EASE THROUGH MID-LATER THIS WEEK, BUT  
MONSOONAL MOISTURE COULD ALLOW FOR MORE RECORD HIGH MINIMUM  
TEMPERATURES. A SERIES OF IMPULSES ROTATING WITHIN AND OVERTOP THE  
RIDGE OFFERS LESS PREDICTABLE TIMINGS INDIVIDUALLY, BUT EACH WILL  
PROVIDE ENHANCED LIFT. THIS MAY BE ESPECIALLY PROBLEMATIC IN UPPER  
DIFFLUENT FLOW/BOUNDARY CONVERGENCE FROM THE CENTRAL  
ROCKIES/PLAINS INTO THE MID-MS VALLEY WHERE CONVECTIVE  
COMPLEXES/THUNDERSTORMS WILL BE FUELED BY INFLOW POOLING MOISTURE  
AND HEAVY/REPEAT CELLS MAY LEAD TO A LOCAL EXCESSIVE RAINFALL  
THREAT.  
 
MUCH OF THIS MEDIUM RANGE FORECAST REMAINS OF HIGH CONFIDENCE  
DURING THIS CYCLE, WITH STRONG AGREEMENT AND CLUSTERING AMONG THE  
MODELS AND ENSEMBLES REGARDING THESE WELL DEFINED AND  
SLOWLY/STEADILY EVOLVING FEATURES. ACCORDINGLY, THE WPC MEDIUM  
RANGE FORECAST SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND  
OF THE LATEST GFS/ECMWF, GEFS AND ECMWF ENSEMBLE MEANS, THE NBM,  
AND 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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