375  
FXUS02 KWBC 251242  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
842 AM EDT TUE JUN 25 2024  
 
VALID 12Z FRI JUN 28 2024 - 12Z TUE JUL 02 2024  
 
...HAZARDOUS HEAT THREATS TO FOCUS ACROSS PARTS OF THE SOUTH NEXT  
WEEKEND AND INTO EARLY NEXT WEEK...  
 
   
..OVERVIEW
 
 
AN UPPER RIDGE CENTERED OVER THE SOUTH WILL EXPAND AND STRENGTHEN  
WITH TIME DURING THE PERIOD, WITH ITS CORE MOST LIKELY SETTLING  
OVER THE LOWER MISSISSIPPI VALLEY THIS WEEKEND AND INTO EARLY NEXT  
WEEK. THIS RIDGE WILL BRING AN INCREASED THREAT FOR HAZARDOUS HEAT  
TO PORTIONS OF THE SOUTHERN U.S. FOR MUCH OF THE PERIOD. TO THE  
NORTH, A SERIES OF SHORTWAVES/TROUGHS WILL PROGRESS FROM WEST TO  
EAST ACROSS THE NORTHERN TIER INTO EARLY NEXT WEEK. SHOWERS AND  
THUNDERSTORMS WILL ACCOMPANY THE ASSOCIATED FRONTAL BOUNDARIES,  
WITH THE BEST CHANCE FOR HEAVY TO EXCESSIVE RAINFALL ACROSS PARTS  
OF THE MIDWEST ON FRIDAY. HEAVY RAINFALL THREATS MAY INCREASE AGAIN  
FOR PARTS OF THE NORTHERN PLAINS TO UPPER MIDWEST EARLY NEXT WEEK  
AS THE NEXT SHORTWAVE REACHES THE REGION.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
OVERALL THE LATEST DYNAMICAL AND MACHINE LEARNING GUIDANCE OFFERS  
BETTER THAN AVERAGE AGREEMENT AND CONTINUITY THROUGH THE PERIOD.  
THERE ARE SOME LINGERING DIFFERENCES IN THE TIMING AND STRENGTH OF  
THE PROGRESSIVE NORTHERN STREAM SHORTWAVES WHICH WOULD HAVE IMPACTS  
ON SENSIBLE WEATHER AND QPF, AND EVEN THESE DETAILS COULD TAKE  
UNTIL THE SHORT RANGE PERIOD TO FULLY RESOLVE. GIVEN THE AGREEMENT,  
A GENERAL MODEL BLEND (WITH THE ENSEMBLE MEANS, ESPECIALLY LATER  
IN THE PERIOD) SHOULD SUFFICE AS A GOOD STARTING POINT FOR THE  
FORECAST.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
A FRONTAL SYSTEM THROUGH THE NORTHERN TIER SHOULD FOCUS THE BEST  
HEAVY TO EXCESSIVE RAINFALL POTENTIAL CENTERED OVER AN AREA  
INCLUDING PARTS OF ILLINOIS/WISCONSIN/IOWA/MISSOURI -- OVERLAPPING  
WITH AREAS WHICH HAVE SEEN SIGNIFICANT RAINFALL RECENTLY. SHOWERS  
AND THUNDERSTORMS ACCOMPANYING THIS SYSTEM SHOULD REACH INTO THE  
EASTERN U.S. AND BACK INTO THE CENTRAL PLAINS NEXT WEEKEND.  
 
COVERAGE OF STORMS ACROSS THE SOUTHWEST SHOULD DECREASE BY FRIDAY  
BUT, RAINFALL COVERAGE MAY INCREASE ONCE AGAIN ESPECIALLY IN NEW  
MEXICO AND THE SOUTHERN ROCKIES OVER THE WEEKEND AND EARLY NEXT  
WEEK WITH A RENEWED THREAT FOR HEAVY RAINFALL AND FLASH FLOODING,  
PARTICULARLY OVER BURN SCARS/SLOT CANYONS.  
 
SHOWERS AND THUNDERSTORMS ASSOCIATED WITH FRONTAL BOUNDARIES MAY  
ALSO LINGER ACROSS THE SOUTHEAST/FLORIDA THROUGH THE PERIOD, BUT  
DRY CONDITIONS/HIGH FFGS SHOULD LIMIT AND FLASH FLOOD THREATS.  
ANOTHER NORTHERN TIER SYSTEM MAY GENERATE AN EPISODE OF POTENTIALLY  
HEAVY RAINFALL OVER PARTS OF THE NORTHERN PLAINS AND UPPER MIDWEST  
AROUND NEXT MONDAY INTO TUESDAY. THIS SYSTEM WILL REQUIRE CLOSE  
MONITORING GIVEN THE REGION'S SENSITIVITY TO ADDITIONAL RAINFALL.  
 
HAZARDOUS HEAT POTENTIAL WILL FOCUS ACROSS THE SOUTH FROM THE  
SOUTHERN PLAINS INTO THE SOUTHEAST MUCH OF THE PERIOD UNDERNEATH  
THE BUILDING AND NEARLY STAGNANT UPPER RIDGE. THIS WILL BRING  
SEVERAL DAYS OF ABOVE NORMAL TEMPERATURES (BOTH DAYTIME HIGHS AND  
OVERNIGHT LOWS) FROM THE SOUTH-CENTRAL PLAINS EASTWARD. A FAIRLY  
BROAD AREA MAY CHALLENGE RECORD WARM LOWS, ESPECIALLY DURING THE  
WEEKEND. MEANWHILE THE MAIN AREA OF COOLER TEMPERATURES WILL BE  
ACROSS THE NORTHERN TIER, WHERE UPPER SHORTWAVES AND SURFACE FRONTS  
PROVIDE SOME RELIEF TO NORMAL SUMMERTIME HEAT.  
 
SANTORELLI/RAUSCH  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM  
RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
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