417  
FXUS02 KWBC 210657  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 AM EDT TUE JUN 21 2022  
 
VALID 12Z FRI JUN 24 2022 - 12Z TUE JUN 28 2022  
 
...EXPANSIVE AREA OF EXCESSIVE HEAT LIKELY TO PERSIST ACROSS THE  
SOUTH THROUGH SATURDAY...  
 
   
..OVERVIEW
 
 
A BROAD UPPER LEVEL RIDGE PARKED OVER THE SOUTHERN U.S. WHEN THE  
PERIOD BEGINS FRIDAY, WILL CONTINUE TO BRING AN EXTENDED PERIOD OF  
EXCESSIVE HEAT AND RECORD TEMPERATURES INTO THE WEEKEND, BUT  
SHOULD FINALLY BEGIN TO WEAKEN AND BREAK DOWN EARLY NEXT WEEK. TO  
THE NORTH, A MODEST TROUGH WILL RIDE AROUND THE TOP OF THE RIDGE  
FROM THE NORTHWEST TO THE MIDWEST, EVENTUALLY AMPLIFYING AS IT  
REACHES THE GREAT LAKES/NORTHEAST LATER IN THE PERIOD ACTING TO  
ERODE THE MASSIVE SOUTHERN HEAT DOME. MONSOONAL MOISTURE WILL  
LIKELY PERSIST OVER THE FOUR CORNERS REGION THROUGH MUCH OF THE  
PERIOD AND COULD CONTRIBUTE TO HEAVIER RAINFALL ALONG THE SOUTHERN  
HALF OF THE ROCKIES BY THE WEEKEND WITH THE ARRIVAL OF A SURFACE  
FRONT AND TRAILING LOW LEVEL UPSLOPE FLOW.  
 
   
..GUIDANCE/PREDICTABILITY EVALUATION
 
 
MODELS AND ENSEMBLES CONTINUE TO SHOW GOOD OVERALL AGREEMENT ON  
THE PATTERN THE FIRST HALF OF THE PERIOD, WHEN THE FOCUS WILL BE  
ON A PERSISTENT AND EXPANSIVE UPPER RIDGE PARKED OVER THE SOUTHERN  
U.S.. THE MOST UNCERTAIN PART OF THE FORECAST CONTINUES TO BE WITH  
DETAILS OF THE TROUGH ROUNDING THE TOP OF THE RIDGE AND INDIVIDUAL  
PIECES OF ENERGY CONTAINED WITHIN ACTING TO EVENTUALLY AMPLIFY THE  
TROUGH AS IT MOVES THROUGH THE GREAT LAKES AND THE NORTHEAST.  
THESE KINDS OF SMALL SCALE UNCERTAINTIES PLAY A ROLE IN THE TIMING  
OF THE LEADING FRONTAL SYSTEM THROUGH THE NORTHERN TIER STATES.  
OTHER AREAS TO MONITOR INCLUDE THE DETAILS OF INITIAL CLOSED  
LOW/TROUGHING OFF THE NORTHEAST COAST LATE THIS WEEK (THOUGH  
MODELS SEEM TO BE COMING TO A CONSENSUS ON THIS COMPARED TO  
PREVIOUS DAYS), AS WELL AS A LARGE CLOSED UPPER LOW APPROACHING  
THE NORTHWEST COAST LATE IN THE PERIOD. THE WPC PROGS RELIED ON A  
BLEND OF THE DETERMINISTIC GUIDANCE FOR THE FIRST HALF OF THE  
PERIOD, WHICH SEEMED TO MITIGATE ANY SMALL SCALE DETAIL  
DIFFERENCES WHICH MAKE TAKE UNTIL THE SHORT RANGE TO RESOLVE. BY  
DAYS 6 AND 7, THE PREFERENCE IS TOWARDS THE ENSEMBLE MEANS AND THE  
CMC WHICH ARE MOST MIDDLE GROUND BETWEEN THE FASTER ECMWF AND  
SLOWER GFS WITH THE MAIN TROUGH THROUGH THE GREAT LAKES AND  
NORTHEAST.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
ANOMALOUSLY HIGH MONSOONAL MOISTURE FOR THIS TIME OF YEAR, LIKELY  
TIED AT LEAST IN PART TO AN EASTERN PACIFIC TROPICAL SYSTEM, WILL  
CONTINUE STREAMING INTO THE FOUR CORNERS STATES INTO EARLY NEXT  
WEEK. LOCALLY HEAVY TO EXCESSIVE RAINFALL IS POSSIBLE,  
PARTICULARLY OVER SENSITIVE BURN SCAR AREAS AND CONSIDERING THE  
MULTIPLE DAY REPEATING NATURE OF THIS ACTIVITY. RAINFALL MAY TREND  
HEAVIER OVER PARTS OF COLORADO/NEW MEXICO BY THE WEEKEND AS A  
FRONT DROPPING SOUTH THROUGH THE REGION AND TRAILING LOW LEVEL  
UPSLOPE FLOW COULD INTERACT WITH THE MOISTURE ALREADY IN PLACE. A  
SHOWERY/STORMY PATTERN COULD ALSO SET UP THROUGH FRIDAY IN PARTS  
OF THE NORTHERN HALF OF THE PLAINS/MISSISSIPPI VALLEY WITH THE  
COMBINATION OF A COLD FRONT PUSHING INTO THE AREA FROM THE WEST  
AND LEADING WARM FRONT LIFTING NORTHEASTWARD. RAINFALL TOTALS WILL  
DEPEND IN PART ON STILL UNCERTAIN FRONTAL TIMING. PROGRESSION OF  
THE PLAINS COLD FRONT SHOULD INCREASE COVERAGE OF  
RAIN/THUNDERSTORMS OVER THE EAST BY THE START OF NEXT WEEK. A  
FRONT SETTLING ACROSS THE SOUTHEAST FRIDAY-SATURDAY SHOULD ALSO  
BRING A PERIOD OF ENHANCED RAINFALL TO PARTS OF THE NORTHERN  
FLORIDA PENINSULA.  
 
LIKELY THE BIGGEST THREAT OF THE MEDIUM RANGE PERIOD WILL BE A  
BROAD AREA OF POTENTIALLY RECORD-BREAKING HEAT ACROSS SOUTHERN  
PARTS OF THE PLAINS INTO THE SOUTHEAST. EXPECT DAILY RECORD MAX OR  
MIN TEMPERATURES BE SET WITHIN THIS AREA, INCLUDING HIGHS  
EXCEEDING 100F AND LOWS WELL INTO THE 70S MEANING LITTLE RELIEF  
OVERNIGHT IN MANY AREAS. TEMPERATURES 10-15F ABOVE NORMAL COULD  
STRETCH FARTHER NORTH INTO MUCH OF THE PLAINS AND MISSISSIPPI AND  
OHIO VALLEYS, MAINLY FRIDAY INTO SATURDAY. THE SOUTH SHOULD  
FINALLY SEE A MODERATING TREND BY THE WEEKEND AND ESPECIALLY EARLY  
NEXT WEEK AS A LEADING FRONT DIPS INTO THE SOUTHEAST AND THEN THE  
LATE WEEK PLAINS FRONT REACHES INTO THE SOUTH AND EAST.  
TEMPERATURES ALONG THE EAST COAST SHOW THE MOST FORECAST SPREAD,  
AND WILL BE DEPENDENT ON THE UPPER PATTERN. RELATIVELY COOLER  
TEMPERATURES WITH WELL BELOW NORMAL HIGHS ARE LIKELY TO BE MOST  
PERSISTENT OVER NEW MEXICO GIVEN THE MONSOONAL CLOUDS AND RAIN  
COVERAGE. THE NORTHERN HIGH PLAINS MAY ALSO SEE COOL HIGHS FROM  
FRIDAY INTO THE WEEKEND, DROPPING INTO COLORADO FROM THE WEEKEND  
INTO EARLY NEXT WEEK WITH SOUTHWARD COLD FRONT PROGRESSION. THE  
WEST COAST STATES SHOULD SEE HIGHS 5-15F ABOVE AVERAGE.  
 
SANTORELLI  
 
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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