550  
FXUS02 KWBC 041849  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
248 PM EDT MON JUL 04 2022  
 
VALID 12Z THU JUL 07 2022 - 12Z MON JUL 11 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 THE UPCOMING WEEKEND 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. THE MULTIPLE DAYS  
OF HIGH HEAT WITH LITTLE NIGHTTIME TEMPERATURE RELIEF WILL  
INCREASE THE POTENTIAL IMPACTS TO SENSITIVE AND MORE VULNERABLE  
GROUPS. ELSEWHERE ACROSS THE CONUS, AROUND THE PERIPHERY OF THIS  
UPPER RIDGE, TROUGHING IS EXPECTED IN THE NORTHWEST AND NORTHEAST  
U.S., WITH PERIODIC ROUNDS OF SHOWERS AND THUNDERSTORMS LIKELY  
MOVING THROUGH THE FLOW. THIS COULD PRODUCE MULTIPLE EPISODES OF  
STRONGER STORMS WITH THE POTENTIAL OF LOCALLY HEAVY RAINFALL  
ACROSS THE OHIO VALLEY TO MID-ATLANTIC AND SOUTHEAST LATE THIS  
WEEK AND THIS WEEKEND.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN GOOD  
AGREEMENT FOR THE LARGE SCALE SETUP AND EVOLUTION FROM LATER THIS  
WEEK THROUGH EARLY NEXT WEEK ACROSS THE CONUS. THE UPPER RIDGE  
STRENGTHENS/BUILDS AND REASSERTS ITSELF OVER THE SOUTHERN PLAINS  
WHILE TROUGHING INITIALLY OVER THE PACIFIC NORTHWEST EVENTUALLY  
WORKS ITS WAY TO DIG A STRONGER TROUGH OVER THE GREAT LAKES AND  
NORTHEAST BY THIS WEEKEND. THE EMBEDDED SHORTWAVES AND MESOSCALE  
DETAILS ARE YET TO BE RESOLVED BUT THERE IS GROWING CONSENSUS FOR  
A STRONG FRONTAL PASSAGE AND SHORTWAVE TROUGH ACROSS THE OHIO  
VALLEY AND MID-ATLANTIC FRIDAY INTO SATURDAY. SOME OF THE LARGE  
MODEL DIFFERENCES WERE WITH THE APPROACH AND PASSAGE OF SHORTWAVE  
ENERGY INTO THE PACIFIC NORTHWEST FRIDAY INTO FRIDAY NIGHT. HERE,  
THE GFS WAS A FASTER OUTLIER COMPARED TO THE REST OF THE GUIDANCE.  
FOR THE FORECAST BLEND, THE DAYS 3-5 WERE COMPOSED OF THE LATEST  
DETERMINISTIC GUIDANCE WHILE FOR DAYS 6-7, HIGHER WEIGHTS OF THE  
GEFS AND ECENS MEANS WERE USED FOR THE TYPICAL MODEL SPREAD AND  
UNCERTAINTY.  
   
..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 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 WITHIN A  
BROAD AREA FROM THE NORTHERN PLAINS/MIDWEST/UPPER GREAT LAKES INTO  
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 PRECLUDES DELINEATING SLIGHT RISK AREAS IN THE  
EXPERIMENTAL DAY 4-5 EXCESSIVE RAINFALL OUTLOOK AT THIS POINT.  
SCATTERED THUNDERSTORMS ARE ALSO LIKELY IN THE SOUTHEAST THROUGH  
THE WEEK, AND THE CURRENT FORECAST SHOWS THE EASTERN PART OF THE  
MAIN FRONT SINKING SOUTHWARD FROM MEANDERING OVER THE MID-ATLANTIC  
INTO THE CAROLINAS AND EVENTUALLY THE GULF COAST BY NEXT WEEKEND,  
LEADING TO MORE FOCUSED RAINFALL IN THE SOUTHEAST AND CLEARING FOR  
THE NORTHEAST BEHIND THE FRONT. AT THE SAME TIME A FRONTAL SYSTEM  
EMERGING INTO THE NORTHERN PLAINS NEXT WEEKEND MAY PROVIDE ADDED  
CONVECTIVE FOCUS OVER THAT REGION ONCE AGAIN. MEANWHILE 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 UPPER 70S TO LOW 80S FOR SOME AREAS) WILL INCREASE  
THE POTENTIAL IMPACTS FROM THIS PROLONGED HEATWAVE TO THE MORE  
SENSITIVE AND VULNERABLE POPULATIONS. MEANWHILE, THE WEST COAST  
COULD SEE COOLER THAN NORMAL CONDITIONS LATE WEEK BEFORE  
MODERATING CLOSER TO AVERAGE, 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/TAYLOR  
 
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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