166  
FXUS02 KWBC 141901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
301 PM EDT SAT MAY 14 2022  
 
VALID 12Z TUE MAY 17 2022 - 12Z SAT MAY 21 2022  
 
...PERSISTENT RECORD-BREAKING HEAT IS LIKELY IN THE SOUTH-CENTRAL  
U.S. NEXT WEEK WITH ANOMALOUS HEAT EXPANDING INTO THE EAST..  
 
   
..OVERVIEW
 
 
UPPER TROUGHING SHOULD SHIFT OUT OF THE EAST TUESDAY-WEDNESDAY  
EARLY IN THE MEDIUM RANGE PERIOD, WITH BROAD RIDGING TO ZONAL FLOW  
BEHIND. 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. 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 REMAINS IN MOSTLY GOOD AGREEMENT WITH THE  
OVERALL PATTERN AT LEAST THROUGH THE MIDDLE OF NEXT WEEK, THOUGH  
UNCERTAINTY IN THE DETAILS LINGERS. DESPITE SOME SMALL SCALE  
SHORTWAVE DIFFERENCES WITHIN THE EASTERN TROUGH, GUIDANCE  
CONTINUES TO SHOW IT LIFTING OUT OF THE U.S. ON WEDNESDAY WITH  
SOME SEPARATION FROM A DEEP CLOSED LOW OVER THE HUDSON BAY THAT  
LOOKS TO LINGER FOR SEVERAL DAYS NEXT WEEK. MODELS STILL VARY WITH  
THE POTENTIAL FOR ANOTHER SHORTWAVE TRAVERSING NEAR THE  
U.S./CANADA BORDER ON WEDNESDAY INTO THURSDAY, WITH THE 00Z GFS  
THE STRONGEST/DEEPEST AND THE 00Z UKMET ON THE DEEPER SIDE AS  
WELL. THE 06Z AND 12Z GFS RUNS BACKED OFF ON THIS FEATURE THOUGH.  
THOUGH THESE SHORTWAVES ARE SMALL SCALE, THEY IMPACT POSITIONS OF  
THE FRONTS AND RAINFALL/CONVECTION. DESPITE THE DIFFERENCES, IT  
SEEMS THE BEST APPROACH WAS A MIDDLE GROUND SO THE WPC FORECAST  
FOR DAYS 3-4 WAS BASED ON COMPOSITE BLEND OF THE DETERMINISTIC  
MODELS LED BY THE 00Z ECMWF, WHICH SEEMED MOST CONSISTENT ACROSS  
THE BOARD.  
 
BY AROUND DAY 5/THURSDAY, OVERALL MODELS AGREE THAT THE UPPER LOW  
SPINNING OFF THE BRITISH COLUMBIA COAST THROUGH THE SHORT TO EARLY  
MEDIUM RANGE PERIOD SHOULD SHIFT SOUTHEAST INTO THE PACIFIC  
NORTHWEST, OR AT LEAST THE ENERGY FROM IT WILL--MODELS ARE QUITE  
VARIABLE WITH THE DETAILS OF EMBEDDED UPPER LOWS WITHIN THE TROUGH  
BEING CREATED BY THIS DIGGING ENERGY, WHICH IS IMPACTED BY  
POTENTIAL INTERACTION WITH THE HUDSON BAY LOW AS WELL. CMC RUNS  
HAVE SHOWN A MORE SHALLOW TROUGH THAT IS FASTER TO MOVE EASTWARD  
COMPARED TO GFS AND ECMWF RUNS. THE NORTHERN PLAINS IS A  
PARTICULARLY UNCERTAIN REGION LATE WEEK AS FAR AS A RIDGE OR  
TROUGH IN THE UPPER FLOW. THE WPC FORECAST FOR THE LATTER PART OF  
THE PERIOD PHASED OUT THE CMC IN FAVOR OF THE GEFS AND EC MEANS,  
TURNING INTO ABOUT AN EVEN BLEND OF THE 00Z ECMWF/EC MEAN/06Z  
GFS/GEFS MEAN BY DAY 7, WHICH MAINTAINED GOOD CONTINUITY FROM THE  
PREVIOUS WPC FORECAST.  
 
   
..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 INTO MIDWEEK 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 THE END OF THE 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  
SOMEWHERE, 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. ROUNDS OF LIKELY LIGHTER RAINFALL ARE  
POSSIBLE ACROSS THE NORTH-CENTRAL U.S. THROUGH THE LATTER HALF OF  
THE WEEK AS WELL. ADDITIONALLY, TROPICAL MOISTURE INCREASING  
ACROSS THE FLORIDA PENINSULA LATE NEXT WEEK COULD LEAD TO A MORE  
RAINY PATTERN THERE.  
 
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.  
 
TATE/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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