922  
FXUS02 KWBC 050651  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
251 AM EDT TUE JUL 05 2022  
 
VALID 12Z FRI JUL 08 2022 - 12Z TUE JUL 12 2022  
 
...PROLONGED HEATWAVE THIS WEEK AND UPCOMING WEEKEND ACROSS  
SOUTHERN PLAINS TO MID SOUTH...  
   
..OVERVIEW
 
 
A PERSISTENT AND STRONG UPPER LEVEL HIGH CENTERED OVER THE  
SOUTHERN U.S. THROUGH THIS WEEK AND INTO EARLY NEXT WEEK WILL KEEP  
VERY HOT TEMPERATURES IN PLACE ACROSS MUCH OF THE CENTRAL CONUS.  
COMBINED WITH THE HUMIDITY, HEAT INDICES ARE LIKELY TO EXCEED  
105-110F IN PLACES AND WITH VERY LITTLE NIGHTTIME RELIEF IN  
TEMPERATURES, A PROLONGED HEATWAVE IS EXPECTED ACROSS THE SOUTHERN  
HALF OF THE PLAINS AND MISSISSIPPI VALLEY. ON THE PERIPHERY OF THE  
UPPER RIDGE, TROUGHING INITIALLY ACROSS THE EASTERN PACIFIC FRIDAY  
WILL SHIFT EASTWARD ACROSS THE NORTHWESTERN TO NORTH-CENTRAL U.S.  
OVER THE WEEKEND INTO EARLY NEXT WEEK, WHILE TROUGHING OVER THE  
NORTHEAST THROUGH THE WEEKEND MAY SHIFT AWAY AROUND MONDAY.  
MULTIPLE IMPULSES MOVING THROUGH THE FLOW NORTH OF THE RIDGE  
SHOULD PRODUCE MULTIPLE EPISODES OF POTENTIALLY STRONG STORMS WITH  
THE POTENTIAL OF LOCALLY HEAVY RAINFALL ACROSS THE OHIO/TENNESSEE  
VALLEYS AND APPALACHIANS TO THE EAST COAST, AS WELL AS ACROSS THE  
NORTHERN PLAINS TO UPPER MIDWEST.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN GOOD  
AGREEMENT FOR THE LARGE SCALE SETUP AND EVOLUTION FOR LATE WEEK AS  
THE CENTER OF THE UPPER HIGH DRIFTS WESTWARD WHILE THE RIDGE AXIS  
STRENGTHENS OVER THE HIGH PLAINS. MODELS FOR THE MOST PART SHOW  
TROUGHING ACROSS THE EAST COAST DEEPENING A BIT INTO THE WEEKEND  
AND PUSHING A COLD FRONT SOUTHWARD. THE TREND HAS BEEN TOWARD A  
SLIGHTLY FASTER FRONT AND THUS QPF WAS FARTHER SOUTH THAN THE  
PREVIOUS ISSUANCE AROUND FRIDAY-SATURDAY. DIFFERENCES IN SMALLER  
SCALE SHORTWAVES REMAIN WITHIN THE TROUGH, WHICH HAVE LOW  
PREDICTABILITY LIKELY EVEN INTO THE SHORT RANGE AND WILL BE  
IMPORTANT FOR THE DETAILS OF RAINFALL AMOUNTS AND PLACEMENT.  
MEANWHILE, TROUGHING WITH ITS AXIS NEAR THE WEST COAST FRIDAY  
SHOULD SHIFT INLAND THIS WEEKEND, BUT WITH SOME DIFFERENCES IN THE  
DETAILS OF TIMING AND ENERGY DISTRIBUTION WITHIN THE TROUGH AS IT  
LIFTS NORTHEAST AND THEN EASTWARD EARLY NEXT WEEK. SPECIFICALLY,  
GFS RUNS HAVE BEEN SOMEWHAT FASTER TO PRESS ENERGY EAST INTO THE  
NORTHERN PLAINS COMPARED TO THE ECMWF RUNS, WHILE THE CMC HAS BEEN  
MORE ALONG THE LINES OF THE GFS, BUT BECOMES FLATTER THAN  
PREFERRED WITH ITS FLOW OVER THE LOWER 48 BY AROUND MONDAY.  
PREFERRED A MIDDLE GROUND SOLUTION BETWEEN THE FASTER GFS AND  
SLOWER ECMWF. MODEL AGREEMENT SEEMS TO ACTUALLY INCREASE SLIGHTLY  
DAY 7/TUESDAY GIVEN THE TROUGH COULD SLIGHTLY AMPLIFY OVER THE  
GREAT LAKES REGION. FOR THE WPC FORECAST BLEND, UTILIZED A  
MULTI-MODEL DETERMINISTIC BLEND EARLY IN THE PERIOD, WITH  
INCREASING PROPORTIONS OF THE GEFS AND ECENS MEANS BY THE LATER  
PERIOD TO ABOUT 40 PERCENT TO SMOOTH OUT SOME MODEL DIFFERENCES  
BUT MAINTAINING GFS AND ECMWF COMPONENTS TO ENHANCE FEATURES.  
 
   
..SENSIBLE WEATHER AND HAZARDS
 
 
SCATTERED SHOWERS AND STORMS ARE LIKELY ACROSS MUCH OF THE U.S.  
FROM THE ROCKIES EASTWARD AT TIMES THIS WEEK INTO EARLY NEXT WEEK,  
WITH ENHANCED TOTALS IN THE VICINITY OF A COUPLE OF FRONTAL  
BOUNDARIES INITIALLY STRETCHING GENERALLY WEST TO EAST ACROSS THE  
NORTHERN HALF OF THE COUNTRY. NORTHWESTERLY FLOW ALOFT AND  
ABUNDANT MOISTURE AND INSTABILITY WILL CREATE A FAVORABLE PATTERN  
FOR MESOSCALE CONVECTIVE SYSTEMS AND HIGH RAINFALL RATES ACROSS  
THE OHIO VALLEY AND APPALACHIANS TO THE EAST COAST. AREAS OF  
EXCESSIVE RAINFALL/FLASH FLOODING ARE POSSIBLE THROUGH THE  
WEEKEND, BUT CONSIDERABLE UNCERTAINTY WITH THE PLACEMENT OF HEAVY  
RAIN AMOUNTS, AS WELL AS THE LIKELY FAST-MOVING NATURE OF THE  
STORMS, PRECLUDES DELINEATING SLIGHT RISK AREAS IN THE  
EXPERIMENTAL DAY 4-5 EXCESSIVE RAINFALL OUTLOOK AT THIS POINT. A  
COLD FRONT IN THE EAST WILL FINALLY BEGIN TO SINK SOUTHWARD OVER  
THE WEEKEND IN RESPONSE TO SLIGHTLY DEEPENING TROUGHING ALOFT.  
THIS COULD PROVIDE ADDITIONAL SUPPORT AND FOCUS FOR THUNDERSTORMS  
ACROSS THE CAROLINAS, SOUTHEAST, AND EVENTUALLY REACHING THE GULF  
COAST, WHILE CLEARING IS EXPECTED OVER THE NORTHEAST BEHIND THE  
FRONT. MEANWHILE, FRONTAL BOUNDARIES AND UPPER-LEVEL ENERGY COULD  
LEAD TO CONVECTION ACROSS THE NORTHERN PLAINS TO UPPER MIDWEST  
THROUGH THE WEEKEND WITH SOME POTENTIAL FOR FLASH FLOODING.  
THUNDERSTORMS MAY PUSH SOUTHEASTWARD FROM THOSE AREAS BY  
MONDAY-TUESDAY ALONG AND AHEAD OF A COLD FRONT. ELSEWHERE,  
MONSOONAL MOISTURE COULD PERSIST THROUGH MUCH OF THE WEEK WITH  
MOIST SOUTHWESTERLY FLOW/EMBEDDED SHORTWAVES LEADING TO MAINLY  
DIURNALLY DRIVEN SHOWERS AND STORMS OVER THE FOUR CORNERS STATES.  
THE SOUTHERN PLAINS AND CALIFORNIA INTO THE GREAT BASIN SHOULD BE  
THE MOST CONSISTENTLY DRY AREAS DURING THE PERIOD.  
 
VERY HOT WEATHER IS EXPECTED TO PERSIST ACROSS THE SOUTHERN HALF  
OF THE PLAINS/MISSISSIPPI VALLEY UNDERNEATH THE STRONG UPPER  
RIDGE/HIGH. HIGH TEMPERATURES NEAR OR EXCEEDING 100F ARE EXPECTED,  
WHICH IS BETWEEN 5 AND 15 DEGREES ABOVE NORMAL. COMBINED WITH THE  
HUMIDITY, DAILY MAXIMUM HEAT INDICES 105-110F+ ARE LIKELY AT TIMES  
ACROSS A LARGE PORTION OF THE MID-MISSISSIPPI VALLEY SOUTHWARD  
INTO THE SOUTHERN PLAINS AND GULF COAST/SOUTHEAST. THE REPEATING  
DAYS OF HIGH HEAT/HUMIDITY AND LACK OF ANY APPRECIABLE NIGHTTIME  
RELIEF (LOWS IN THE UPPER 70S TO LOW 80S FOR SOME AREAS) WILL  
INCREASE THE POTENTIAL FOR IMPACTS FROM THIS PROLONGED HEATWAVE TO  
THE MORE SENSITIVE AND VULNERABLE POPULATIONS. SOME DAILY RECORD  
HIGH TEMPERATURES ARE POSSIBLE, PARTICULARLY FOR WARM LOWS.  
MEANWHILE, THE WEST COAST COULD SEE COOLER THAN NORMAL CONDITIONS  
LATE WEEK BEFORE MODERATING CLOSER TO AVERAGE AND EVENTUALLY ABOVE  
AVERAGE EARLY NEXT WEEK, WHILE THE DESERT SOUTHWEST SHOULD SEE  
NEAR NORMAL TEMPERATURES BECOMING A FEW DEGREES ABOVE AVERAGE.  
PARTS OF THE EAST MAY SEE SLIGHTLY BELOW NORMAL TEMPERATURES  
SPREADING SOUTH THIS WEEKEND INTO MONDAY BEHIND A COLD FRONT.  
 
TATE  
 
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, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE  
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/#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  
 

 
 

 
 
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