282  
FXUS02 KWBC 150701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SUN MAY 15 2022  
 
VALID 12Z WED MAY 18 2022 - 12Z SUN MAY 22 2022  
 
...PERSISTENT RECORD-BREAKING HEAT IS LIKELY IN THE SOUTH-CENTRAL  
U.S. THROUGH THIS WEEK WITH ANOMALOUS HEAT EXPANDING INTO THE EAST  
BY NEXT WEEKEND...  
 
   
..OVERVIEW
 
 
UPPER TROUGHING SHOULD SHIFT OUT OF THE NORTHEAST AS THE PERIOD  
BEGINS ON WEDNESDAY, WITH BROAD RIDGING TO ZONAL FLOW BEHIND  
ACROSS THE REST OF THE LOWER 48. THE PATTERN IS EXPECTED TO  
AMPLIFY LATER IN THE WEEK AS UPPER TROUGHING DIGS IN THE WEST,  
YIELDING COOLER TEMPERATURES AND LOWERING SNOW LEVELS IN A ROUND  
OF PRECIPITATION SPREADING ACROSS THE NORTHWEST. STUBBORN RIDGING  
ACROSS THE SOUTH WILL CONTINUE TO PROMOTE UNSEASONABLY HOT  
WEATHER, WITH THE MOST PERSISTENT AND RECORD-BREAKING HEAT  
CENTERED IN TEXAS AND LOUISIANA. WARMER THAN NORMAL TEMPERATURES  
ARE FORECAST TO SPREAD EASTWARD AS THE RIDGE AMPLIFIES AHEAD OF  
THE TROUGH IN THE WEST, AND THE HEAT SHOULD FINALLY BREAK BY NEXT  
WEEKEND ACROSS THE SOUTH. THE BEST FOCUS FOR SHOWERS AND  
THUNDERSTORMS SHOULD BE ALONG A QUASI-STATIONARY BOUNDARY FROM THE  
CENTRAL PLAINS INTO THE OHIO VALLEY, WHILE SOME ROUNDS OF RAIN ARE  
ALSO POSSIBLE IN THE NORTH-CENTRAL U.S. AND SHOWER/THUNDERSTORM  
CHANCES WILL INCREASE IN FLORIDA LATE NEXT WEEK.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
RECENT MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT EARLY IN THE  
PERIOD WITH EJECTING TROUGH ENERGY IN THE NORTHEAST AND ALSO A  
WEAK SHORTWAVE THROUGH THE NORTHERN TIER WEDNESDAY-THURSDAY. AFTER  
THIS, MODELS AGREE THE PATTERN SHOULD BECOME MORE AMPLIFIED LATE  
PERIOD, BUT WITH VARYING DEGREES OF SEPERATION BETWEEN ANOTHER  
STRONGER SHORTWAVE ACROSS THE NORTHERN PLAINS AND ALSO ENERGY  
DIGGING ACROSS THE INTERMOUNTAIN WEST. YESTERDAYS 12Z RUN OF THE  
CMC WAS THE GREATEST OUTLIER SHOWING A FASTER AND MORE CONHESIVE  
TROUGH THROUGH THE WEST LATE WEEK, WHILE THE ECMWF AND GFS (AND  
UKMET BEFORE IT PHASES OUT AFTER DAY 5) EXHIBITED BETTER  
SEPERATION OF STREAMS. HOWEVER, THE 12Z ECMWF WAS MORE BULLISH ON  
DIGGING THE SOUTHERN STREAM ENERGY FARTHER SOUTH INTO THE  
SOUTHWEST, WHILE SUBSEQUENTLY BUIDLING A STRONGER RIDGE ACROSS THE  
EAST. TODAYS 00Z ECMWF (AVAILABLE AFTER FORECAST GENERATION TIME)  
CAME IN A LITTLE LESS AMPLIFIED AND MORE IN LINE WITH THE GFS AND  
CMC, BUT THERE IS STILL SO MUCH UNCERTAINTY IN THE DETAILS. WPCS  
FORECAST FOR TONIGHT USED A BLEND OF THE DETERMINISTIC MODELS  
EARLY ON TRENDING QUICKLY TOWARDS THE ENSEMBLE MEANS LATE PERIOD  
WHICH RESULTED IN A GOOD MIDDLE GROUND APPROACH. SOME  
DETERMINISTIC ECMWF AND GFS WERE MAINTAINED THROUGH DAY 7 THOUGH  
JUST FOR SOME ADDED SYSTEM DEFINITION TO THE NORMALLY WASHED OUT  
MEANS.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL RIDGING ACROSS THE SOUTHERN PLAINS AND THEN EVENTUALLY  
RISING HEIGHTS FARTHER EAST OVER THE DEEP SOUTH WILL PROMOTE A  
BROAD AREA OF HEAT ACROSS MUCH OF THE SOUTHERN U.S. DURING THE  
PERIOD. THE GREATEST AND MOST LASTING ANOMALIES THROUGH THE PERIOD  
SHOULD BE OVER TEXAS (PERSISTING FROM THE SHORT RANGE TIME FRAME)  
WHERE SOME LOCATIONS COULD SEE HIGHS UP TO 15-25F ABOVE NORMAL,  
WITH NUMEROUS DAILY RECORD HIGHS LIKELY. PARTS OF THE SOUTHWEST  
INTO THE CENTRAL GREAT BASIN AND SOUTHERN/CENTRAL ROCKIES CAN  
EXPECT HIGHS AROUND 10F ABOVE AVERAGE ON WEDNESDAY BEFORE A  
COOLING TREND AS THE DEEPER TROUGHING PRESSES INLAND. HOWEVER,  
WARM TO HOT TEMPERATURES COULD INCREASE FOR THE SOUTHEASTERN  
QUADRANT OF THE U.S. LATER NEXT WEEK, WITH POTENTIAL FOR DAILY  
RECORD HIGHS, AND WARMER THAN AVERAGE TEMPERATURES BY 10-20F  
SHOULD EXPAND IN COVERAGE ACROSS THE OHIO VALLEY TO EASTERN  
SEABOARD BY NEXT WEEK.  
 
A WARM FRONT LIFTING THROUGH THE MID-MISSISSIPPI VALLEY AND OHIO  
VALLEY WILL PROVIDE A FOCUS FOR MULTIPLE AREAS OF SHOWERS AND  
STORMS/CONVECTIVE COMPLEXES DURING THE MIDDLE TO LATTER PART OF  
NEXT WEEK. THE INGREDIENTS ARE IN PLACE FOR HEAVY RAINFALL, THOUGH  
THE SPECIFICS OF COVERAGE AND AMOUNTS ARE UNCERTAIN, BUT AT LEAST  
A LOCALIZED FLOOD THREAT IS LIKELY ESPECIALLY IF HEAVY RAIN FALLS  
IN AREAS THAT ARE SENSITIVE TO ADDITIONAL RAINFALL. ORGANIZED  
RAINFALL, HEAVY AT TIMES, IS LIKELY ALONG A FRONTAL BOUNDARY  
THROUGH THE NORTH-CENTRAL U.S. LATER IN THE WEEK WITH POTENTIAL  
FOR AT LEAST LOCALIZED FLOOD AND FLASH FLOOD THREATS GIVEN VERY  
WET ANTECEDENT CONDITIONS ACROSS THAT REGION. ADDITIONALLY,  
TROPICAL MOISTURE INCREASING ACROSS THE FLORIDA PENINSULA LATE  
NEXT WEEK COULD LEAD TO A MORE RAINY PATTERN FOR THE SUNSHINE  
STATE.  
 
AFTER A COUPLE OF INITIAL FRONTS CROSSING THE NORTHWEST, THE MAIN  
WELL-DEFINED FRONT AHEAD OF THE DEEPENING TROUGH WILL BRING  
UNSEASONABLY COOL TEMPERATURES TO THE NORTHWEST AND EXPANDING INTO  
THE NORTHERN ROCKIES AND HIGH PLAINS BY LATE WEEK. THIS WILL ALSO  
PROVIDE SUPPORT FOR A NOTABLE ROUND OF PRECIPITATION, WITH  
LOWERING SNOW LEVELS IN THE CASCADES TO NORTHERN ROCKIES AS THE  
WEEK PROGRESSES, WITH SOME CHANCE OF SNOW EVEN INTO NORTHERN PARTS  
OF THE HIGH PLAINS, THOUGH WITH VERY LOW CONFIDENCE AT THIS POINT.  
 
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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