889  
FXUS02 KWBC 140649  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
247 AM 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 PERIODS OF ANOMALOUS HEAT FOR THE REST OF THE  
SOUTHERN TIER AS WELL..  
 
   
..OVERVIEW
 
 
UPPER TROUGHING SHOULD BE EXITING THE EAST EARLY NEXT WEEK, WITH  
UNCERTAIN SHORTWAVE ENERGY SLIDING THROUGH THE GREAT LAKES AND  
NORTHEAST AROUND THURSDAY-FRIDAY. AFTER THIS, MODELS SUGGEST THE  
PATTERN OVER THE CONUS MAY AGAIN AMPLIFY AS TROUGHING DIGS INTO  
THE WEST AND UPPER RIDGING EXPANDS INTO THE EAST. MEANWHILE TO THE  
SOUTH, STRONG AND STUBBORN RIDGING WILL CONTINUE TO PROMOTE  
UNSEASONABLY HOT WEATHER ACROSS THE SOUTHERN U.S., WITH THE MOST  
PERSISTENT AND RECORD-BREAKING HEAT CENTERED IN TEXAS AND  
LOUISIANA. THE BEST FOCUS FOR SHOWERS AND THUNDERSTORMS SHOULD BE  
ALONG A QUASI-STATIONARY BOUNDARY FROM THE CENTRAL PLAINS INTO THE  
OHIO VALLEY, WHILE THE WEST SEES COOLING TEMPERATURES IN RESPONSE  
TO UPPER TROUGHING AS THE WEEK PROGRESSES, ALONG WITH LOWERING  
SNOW LEVELS BY MIDWEEK WITHIN ROUNDS OF PRECIPITATION.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
RECENT MODEL GUIDANCE REMAINS IN MOSTLY GOOD AGREEMENT WITH THE  
OVERALL PATTERN DURING THE MEDIUM RANGE PERIOD, BUT WITH PLENTY OF  
UNCERTAINTIES SURROUNDING SMALLER SCALE FEATURES AND EVOLUTION OF  
THE TROUGH OUT WEST LATER IN THE PERIOD. TIMING OF THE TROUGH OUT  
OF THE EAST ON TUESDAY HAS IMPROVED, WITH MODELS SUGGESTING MORE  
SEPARATION BETWEEN THIS AND A DEEP CLOSED LOW OVER HUDSON BAY  
WHICH LOOKS TO LINGER FOR SEVERAL DAYS NEXT WEEK. EVEN THOUGH THE  
BULK OF THIS FEATURE IS WELL NORTH OF THE CONUS, IT SHOULD PLAY A  
ROLE IN THE EVOLUTION OF THE PATTERN UPSTREAM OVER THE WEST.  
MODELS ARE SPLIT ON HOW STRONG A LEADING SHORTWAVE WILL BE ACROSS  
THE NORTHERN TIER WEDNESDAY-FRIDAY WITH THE GFS AND UKMET  
STRONGEST, AND ECMWF AND CMC FAIRLY WEAK. GUIDANCE SHOWS SOME  
VARYING RUN TO RUN CONTINUITY SUGGESTING LOW CONFIDENCE ON THE  
SPECIFICS OF THIS FEATURE WHICH HAS IMPORTANT IMPLICATIONS ON  
FRONTAL POSITIONS 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, THOUGH WITH MORE EMPHASIS TOWARDS THE ECMWF  
WHICH SEEMED MOST CONSISTENT ACROSS THE BOARD.  
 
BIG UNCERTAINTIES BEGIN AS EARLY AS DAY 5 WITH A CLOSED LOW OFF  
THE BRITISH COLUMBIA COAST WHICH LOOKS TO DIG INTO THE WESTERN  
U.S. LATE NEXT WEEK. THE 12Z/YESTERDAY CMC WAS SIGNIFICANTLY  
WEAKER/LESS AMPLIFIED WITH THIS TROUGH THROUGH THE NORTHWEST WITH  
MORE EVENTUAL INTERACTION/PHASING WITH THE LOW OVER HUDSON BAY,  
BUT THE NEWEST 00Z RUN (AVAILABLE AFTER FORECAST PRODUCTION TIME)  
CAME IN A BIT MORE AMPLIFIED AND CLOSER TO THE CONSENSUS. RECENT  
RUNS OF THE GFS AND ECMWF (ALONG WITH THE ENSEMBLES) SHOW A MORE  
AMPLIFIED PATTERN ACROSS THE CONUS BY NEXT SATURDAY, BUT DIFFER IN  
THE DETAILS OF HOW TO GET THERE. WPC LEANED ON THE ENSEMBLE MEANS  
TO HELP TEMPER THESE SMALLER SCALE DIFFERENCES, BUT WITH AT LEAST  
HALF GFS/ECMWF TO HELP WITH SYSTEM DEFINITION.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
INITIAL RIDGING ACROSS THE SOUTHWEST AND 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 10-15F ABOVE AVERAGE FOR THE FIRST  
HALF OF THE WEEK 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.  
 
A WARM FRONT LIFTING THROUGH THE MID-MISSISSIPPI VALLEY AND OHIO  
VALLEY WILL PROVIDE 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, BUT PLENTY OF UNCERTAINTY REMAINS IN THE GUIDANCE WITH  
RESPECT TO COVERAGE AND AMOUNTS, ALTHOUGH IT SEEMS LIKELY THIS  
SHOULD PRESENT AT LEAST A LOCALIZED FLOOD THREAT GIVEN RECENT  
HEAVY RAINS IN SOME OF THESE AREAS.  
 
THE SERIES OF SURFACE WAVES/FRONTS AHEAD OF THE  
APPROACHING/ARRIVING EASTERN PACIFIC UPPER TROUGH WILL KEEP THE  
PACIFIC NORTHWEST ON THE COOL SIDE WITH FREQUENT EPISODES OF  
PRECIPITATION. THE TROUGH SHOULD REACH FAR ENOUGH EASTWARD TO  
BRING HIGHS DOWN TO 10-20F BELOW NORMAL OVER THE  
NORTHWEST/NORTHERN ROCKIES BY NEXT THURSDAY-FRIDAY. SNOW LEVELS  
SHOULD LOWER AS THE WEEK GOES ON AS THE MAIN UPPER TROUGH ARRIVES.  
A LEADING WELL DEFINED FRONT WILL PRESS EAST ACROSS THE REGION,  
WITH RAINFALL LIKELY ARRIVING INTO PARTS OF THE NORTH-CENTRAL  
PLAINS BY NEXT WEEKEND.  
 
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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