213  
FXUS02 KWBC 051840  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
239 PM 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 AND  
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  
DEEPENING TROUGHING ACROSS THE EAST COAST INTO THE WEEKEND WHICH  
SHOULD HELP PUSH THE COLD FRONT SOUTHWARD. OUT WEST, A COUPLE OF  
SHORTWAVES SHOULD SLIDE INLAND, THE FIRST ON FRIDAY AND THEN  
ANOTHER THIS WEEKEND WHICH IS FORECAST TO ESSENTIALLY RIDE THE  
SOUTHERN U.S. RIDGE ACROSS THE FAR NORTHERN TIER AND POSSIBLY  
AMPLIFY SOME AS IT MOVES INTO THE GREAT LAKES EARLY NEXT WEEK.  
THERE ARE SOME TIMING QUESTIONS WITH THIS SECOND WAVE, WHICH ALSO  
AFFECTS HOW QUICKLY THE INITIAL TROUGH OVER THE EAST IS ABLE TO  
MOVE OUT AHEAD OF IT. THE CMC IS A LITTLE FASTER WITH THE WAVE AS  
IT COMES INTO THE UPPER GREAT LAKES NEXT MONDAY-TUESDAY SO IT WAS  
EXCLUDED FROM THE BLEND AFTER DAY 5. WPC USED A BLEND OF THE  
DETERMINISTIC GUIDANCE FOR DAYS 3-5, AMIDST GOOD AGREEMENT,  
TRANSITIONING TO A 50/50 MODEL/ENSEMBLE MEAN BLEND BY DAY 7  
BETWEEN THE GFS/ECMWF AND ECENS/GEFS MEANS. THIS APPROACH  
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.  
 
   
..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 FROM THE  
OHIO VALLEY AND APPALACHIANS TO THE EAST COAST. AREAS OF EXCESSIVE  
RAINFALL/FLASH FLOODING ARE POSSIBLE THROUGH THE WEEKEND, WITH  
CONSIDERABLE UNCERTAINTY WITH THE EXACT PLACEMENT OF HEAVY RAIN  
AMOUNTS GIVEN THE FAST-MOVING NATURE OF STORMS. HOWEVER, DESPITE  
THIS, A SLIGHT RISK WAS ADDED TO THE EXPERIMENTAL DAY 4 EXCESSIVE  
RAINFALL OUTLOOK FOR THE CENTRAL APPALACHINAS GIVEN HEAVY RAINFALL  
SENSITIVITY AND ENOUGH OF A CONSISTENT SIGNAL IN THE MODELS FOR  
HEAVIER ACTIVITY IN THAT REGION. 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. GIVEN THE  
POTENTIAL FOR SEVERAL ROUNDS OF HEAVY RAINFALL IN THE SHORT RANGE  
FOR PARTS OF EASTERN NORTH CAROLINA, A SECOND SLIGHT RISK WAS  
ADDED TO THE DAY 4 ERO FOR THAT AREA. 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.  
 
SANTORELLI/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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