671  
FXUS02 KWBC 060651  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
250 AM EDT WED JUL 06 2022  
 
VALID 12Z SAT JUL 09 2022 - 12Z WED JUL 13 2022  
 
...A PROLONGED HEAT WAVE WILL LAST THROUGH EARLY NEXT WEEK ACROSS  
THE SOUTHERN PLAINS AND MID-SOUTH...  
   
..OVERVIEW
 
 
A PERSISTENT AND STRONG UPPER LEVEL HIGH CENTERED OVER THE  
SOUTHERN U.S. THROUGH THIS WEEK DRIFTING INTO THE FOUR CORNERS  
REGION 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 HEAT WAVE IS  
EXPECTED ACROSS THE SOUTHERN HALF OF THE PLAINS AND MISSISSIPPI  
VALLEY. ON THE PERIPHERY OF THE UPPER RIDGE, TROUGHING IS FORECAST  
OVER THE NORTHEAST THIS WEEKEND WHILE ANOTHER TROUGH ACROSS THE  
WEST COAST SATURDAY WILL QUICKLY TRACK ACROSS THE NORTH-CENTRAL  
U.S. AND REDEVELOP TROUGHING CENTERED IN THE NORTHEAST QUADRANT OF  
THE LOWER 48 BY TUESDAY-WEDNESDAY. ROUNDS OF STORMS ARE EXPECTED  
TO PUSH SOUTHWARD AHEAD OF A COLD FRONT ACROSS THE SOUTHEASTERN  
U.S. THROUGH THE WEEKEND, WITH FLASH FLOODING POSSIBLE. THE  
NORTHERN PLAINS TO UPPER MIDWEST SHOULD ALSO SEE RAIN AND  
THUNDERSTORM CHANCES, WHILE SOME MONSOONAL MOISTURE CONTINUES TO  
FLOW INTO THE SOUTHWEST.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN GOOD  
AGREEMENT FOR THE LARGE SCALE SETUP AND EVOLUTION FOR THIS WEEKEND  
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. THEN WHILE MODELS  
AGREE THAT THE WEST COAST TROUGHING SATURDAY SHOULD QUICKLY LIFT  
AND DEAMPLIFY SOMEWHAT AS IT TRACKS NEAR THE U.S./CANADA BORDER,  
THERE ARE SOME DIFFERENCES IN ENERGY EVOLUTION WITH IMPULSES  
STEMMING FROM THE ORIGINAL TROUGH BUT ALSO FROM CANADA, WHICH ARE  
ALL FORECAST TO COMBINE SOMEHOW TO AMPLIFY TROUGHING WITH ITS AXIS  
AROUND THE GREAT LAKES TUESDAY-WEDNESDAY. AT LEAST GUIDANCE HAS  
AGREEMENT ON THE LARGE SCALE FOR THIS AMPLIFYING TROUGH AND  
SURFACE LOW DEVELOPMENT IN SOUTH-CENTRAL CANADA, BUT THE DETAILS  
WILL IMPACT FRONTAL POSITIONS AND PLACEMENT OF RAINFALL. THE  
UPDATED WPC FORECAST HAS TRENDED A LITTLE FASTER WITH THE LOW  
PRESSURE/FRONTAL SYSTEM AND THE RAINFALL FORECAST IN THE  
NORTH-CENTRAL U.S. DESPITE THE MESOSCALE DIFFERENCES, GIVEN THE  
SYNOPTIC SCALE AGREEMENT, THE WPC FORECAST BLEND WAS ABLE TO USE  
THE DETERMINISTIC GUIDANCE EARLY IN THE PERIOD AND MAINTAINED A  
MAJORITY DETERMINISTIC BLEND THROUGH THE WHOLE PERIOD, TRADING THE  
UKMET FOR THE EC ENSEMBLE MEAN DAYS 6-7.  
 
   
..SENSIBLE WEATHER AND HAZARDS
 
 
AS THE EASTERN PART OF A COLD FRONT FINALLY BEGINS TO DROP  
SOUTHWARD THIS WEEKEND ALONG THE EAST COAST, IT WILL PROVIDE A  
FOCUS FOR ANOMALOUSLY HIGH MOISTURE TO POOL IN THE SOUTHEAST AND  
LEAD TO HEAVY RAINFALL AND POTENTIALLY FLASH FLOODING THIS  
WEEKEND. A SLIGHT RISK WAS ADDED TO THE EXPERIMENTAL DAY 4  
EXCESSIVE RAINFALL OUTLOOK OVER COASTAL NORTH CAROLINA AND  
PORTIONS OF SOUTH CAROLINA WHERE RAINFALL AND RAIN RATES COULD BE  
THE HEAVIEST. AS THE FRONT GRADUALLY SINKS SOUTH AND DISSIPATES,  
THE BEST RAIN CHANCES WILL SHIFT TOWARD THE GULF COAST AND  
FLORIDA, WHILE CLEARING IS EXPECTED FOR THE NORTHEAST AND  
MID-ATLANTIC BEHIND THE FRONT. FARTHER NORTH, SHORTWAVE ENERGY AND  
A FRONTAL SYSTEM OR TWO ARE FORECAST TO LEAD TO RAIN AND  
THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST THIS  
WEEKEND. WHILE MOISTURE IS HIGH THERE, THE POSSIBLY QUICKER STORM  
MOTIONS AND THE UNCERTAINTY IN THE DETAILS OF THE  
SHORTWAVES/FRONTAL PLACEMENT PRECLUDE ANY SLIGHT RISK ISSUANCES  
THERE. RAINFALL ACTIVITY SHOULD SHIFT TOWARD THE GREAT LAKES  
REGION AND THEN THE NORTHEAST MONDAY-TUESDAY, WITH SCATTERED  
STORMS ALSO POSSIBLE ALONG THE TRAILING COLD FRONT IN THE OHIO  
VALLEY AND EVEN POSSIBLY BACK INTO CENTRAL PARTS OF THE PLAINS AND  
MISSISSIPPI VALLEY. ELSEWHERE, MONSOONAL MOISTURE COULD PERSIST  
EVEN INTO NEXT WEEK WITH MOIST SOUTHWESTERLY FLOW/EMBEDDED  
SHORTWAVES LEADING TO MAINLY DIURNALLY DRIVEN SHOWERS AND STORMS  
OVER THE FOUR CORNERS STATES. THUS THE WEST COAST SHOULD BE THE  
MOST CONSISTENTLY DRY AREA THROUGH 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 THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY THROUGH AT  
LEAST EARLY NEXT WEEK, WHILE THE SOUTHEAST MAY ALSO EXPERIENCE  
THIS HEAT SATURDAY, THOUGH SHORT-LIVED THERE AHEAD OF THE COLD  
FRONT BRINGING IN SLIGHTLY BELOW NORMAL TEMPERATURES. 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. THE NORTHERN/CENTRAL HIGH PLAINS CAN ALSO EXPECT WARMER THAN  
NORMAL TEMPERATURES OVER THE WEEKEND BUT APPROACHING CLOSER TO  
NORMAL AS THE WORKWEEK BEGINS. AS THE UPPER RIDGE DRIFTS WESTWARD,  
THE WEST SHOULD SEE TEMPERATURES WARMING FROM SLIGHTLY BELOW  
NORMAL TO ABOVE NORMAL (BY 10+ DEGREES IN THE NORTHWEST) AS THE  
FIRST HALF OF NEXT WEEK PROGRESSES.  
 
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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