956  
FXUS02 KWBC 070702  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SAT MAY 07 2022  
 
VALID 12Z TUE MAY 10 2022 - 12Z SAT MAY 14 2022  
 
...BLOCKY PATTERN NEXT WEEK TO SUPPORT RECORD HEAT OVER THE  
SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY INTO THE MIDWEST ALONG  
WITH EPISODES OF CENTRAL U.S. CONVECTION...  
   
..OVERVIEW
 
 
GUIDANCE CONTINUES TO SHOW A BLOCKY PATTERN DURING THE PERIOD.  
MEAN RIDGING ALOFT WILL SUPPORT A PROLONGED PERIOD OF WELL ABOVE  
NORMAL TEMPERATURES (CHALLENGING DAILY RECORDS OVER SOME AREAS)  
OVER THE MISSISSIPPI VALLEY/CENTRAL-SOUTHERN PLAINS EXTENDING INTO  
NEW ENGLAND. AT THE SAME TIME MEAN TROUGHING CONTAINING A COUPLE  
SEPARATE FEATURES WILL PRODUCE CHILLY AND UNSETTLED WEATHER OVER  
THE WEST, WITH WAVES/FRONTS AND A DRY LINE PROMOTING EPISODES OF  
RAIN AND THUNDERSTORMS BETWEEN THESE TWO REGIMES. MEANWHILE A  
RETROGRADING UPPER RIDGE OVER THE ATLANTIC WILL LIKELY PUSH AN  
INITIAL WESTERN ATLANTIC UPPER LOW BACK TOWARD THE SOUTHERN PART  
OF THE EAST COAST, BRINGING AN INCREASE OF MOISTURE TO CENTRAL AND  
SOUTHERN PORTIONS OF THE EAST LATE WEEK INTO THE WEEKEND.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
ONCE AGAIN THE MOST PRONOUNCED GUIDANCE DIFFERENCES IN THE  
FORECAST INVOLVE THE FEATURES WITHIN THE WESTERN MEAN TROUGH, WITH  
SIGNIFICANTLY VARYING IDEAS FOR THE COMBINATION OF A FAIRLY SHARP  
TROUGH/EMBEDDED LOW ALONG OR JUST INLAND FROM THE WEST COAST  
THROUGH MIDWEEK AND TRAILING NORTHEASTERN PACIFIC ENERGY THAT  
SHOULD REACH THE NORTHWEST AFTER MIDWEEK. EVEN WITH SOME  
DIFFERENCES IN HANDLING OF THE TRAILING ENERGY AMONG RECENT RUNS,  
THE GFS/CMC HAVE CONSISTENTLY BEEN ON THE FASTER SIDE OF THE  
ENVELOPE WITH EJECTION OF THE LEADING SYSTEM. ECMWF RUNS HAVE BEEN  
SLOWER BUT THE 12Z RUN WAS A BIT FASTER THAN THE PRIOR 00Z VERSION  
DUE TO TRENDING FASTER WITH THE TRAILING FLOW. THE 12Z UKMET AND  
TO SOME DEGREE THE NEW 00Z RUN ARE SLOWER TO BRING IN THE UPSTREAM  
TROUGHING, LEADING TO SLOW PROGRESSION OF THE LEADING FEATURE AND  
A RATHER FAR SOUTH TRACK OF THE UPPER LOW IN THE NEW RUN BY LATE  
THURSDAY. PREFERENCE CONTINUES TO BE FOR AN INTERMEDIATE TIMING  
UNTIL SOLUTIONS GRAVITATE MORE TO ONE SIDE OF THE SPREAD. THE NEW  
00Z ECMWF HAS ADJUSTED NOTICEABLY FASTER, TO A TIMING JUST AHEAD  
OF THE FAVORED COMPROMISE. BY DAY 7 SATURDAY THERE HAS ALSO BEEN  
QUITE A BIT OF VARIABILITY IN THE MODELS FOR HOW AMPLIFIED THE  
TRAILING ENERGY BECOMES AS IT CROSSES THE WEST, WITH A BLEND/MEAN  
APPROACH PROVIDING A REASONABLE STARTING POINT. TELECONNECTIONS  
RELATIVE TO THE CORE OF POSITIVE HEIGHT ANOMALIES OVER  
SOUTHEASTERN CANADA BY LATE IN THE PERIOD SUPPORT THE RESIDUAL  
WESTERN TROUGHING.  
 
THE UPPER LOW RETROGRADING BACK TO THE EAST COAST, ALONG WITH  
ASSOCIATED SURFACE LOW AND WARM FRONT, EXHIBIT TYPICAL DETAIL  
DIFFERENCES IN THE GUIDANCE, WITH A CONSENSUS APPROACH AMONG  
LATEST MODELS/MEANS OFFERING A REASONABLE STARTING POINT AND  
DECENT CONTINUITY. THE 12Z GFS APPEARED TO BE A LITTLE QUICK TO  
LIFT IT NORTHWESTWARD AND OPEN IT UP LATE IN THE PERIOD THOUGH. IF  
ANYTHING, LATEST TRENDS SEEM TO BE NUDGING THE UPPER LOW CENTER A  
LITTLE FARTHER SOUTH.  
 
THE UPDATED FORECAST STARTED WITH A 12Z/18Z OPERATIONAL MODEL  
BLEND ON TUESDAY BUT THEN PHASED OUT THE UKMET DUE TO QUESTION  
MARKS WITH ITS NORTHEASTERN PACIFIC PATTERN AND ITS EVENTUAL  
EFFECT ON THE WEST, FOLLOWED BY THE CMC BY THURSDAY DUE TO ITS  
OVERALL FASTER PROGRESSION. 18Z GEFS/12Z ECMWF MEAN WEIGHT  
STEADILY INCREASED MID-LATE PERIOD WHILE VARYING PARTS OF THE 12Z  
ECMWF AND 18Z/12Z GFS (WITH SOME MANUAL EDITS) HELPED CENTER THE  
WESTERN/CENTRAL U.S. EVOLUTION.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
STRONG UPPER RIDGING WILL LEAD TO PERSISTENT MUCH ABOVE NORMAL  
TEMPERATURES OVER THE CENTRAL-SOUTHERN PLAINS AND MOST OF THE  
MISSISSIPPI VALLEY THROUGH THE WEEK, WITH SOME OF THIS WARMTH ALSO  
EXPANDING THROUGH THE GREAT LAKES AND NORTHEAST. EXPECT A BROAD  
AREA OF HIGHS/MORNING LOWS 10-20F ABOVE NORMAL WITH SOME LOCALIZED  
AREAS REACHING HIGHER THAN THAT. NUMEROUS DAILY RECORDS ARE LIKELY  
THROUGH THE WEEK OVER THE SOUTHERN PLAINS AND LOWER MISSISSIPPI  
VALLEY, AND MAY ALSO EXTEND INTO THE CENTRAL PLAINS/MIDWEST  
ESPECIALLY AROUND TUESDAY/WEDNESDAY. TEMPERATURES COULD ALSO  
CHALLENGE RECORD HIGHS OVER A FEW PLACES IN THE NORTHEAST LATE IN  
THE WEEK. HIGHEST HEAT INDEX VALUES WILL BE OVER SOUTHERN TEXAS ON  
TUESDAY BUT THE COMBINATION OF HEAT AND HUMIDITY MAY STILL PRODUCE  
MAXIMUM HEAT INDEX VALUES OVER 100F AT SOME LOCATIONS JUST INLAND  
FROM THE WESTERN GULF COAST THROUGH AT LEAST FRIDAY. EXCESSIVE  
HEAT, GUSTY WINDS, AND DRY CONDITIONS SHOULD LEAD TO AN ELEVATED  
FIRE WEATHER THREAT ACROSS PARTS OF THE SOUTHERN HIGH PLAINS  
THROUGH AT LEAST MID-WEEK.  
 
THE WEST WILL SEE UNSEASONABLY COOL AND UNSETTLED CONDITIONS NEXT  
WEEK, ALBEIT WITH A GRADUAL MODERATING TREND AS UPPER TROUGHING  
BECOMES LESS AMPLIFIED. COLDEST ANOMALIES WILL BE ON  
TUESDAY/WEDNESDAY OVER CALIFORNIA AND THE WESTERN GREAT BASIN WITH  
HIGHS 10-20F OR SO BELOW NORMAL. TEMPERATURES MAY REBOUND TO  
MODERATELY ABOVE NORMAL LEVELS OVER CALIFORNIA AND THE SOUTHWEST  
BY NEXT SATURDAY WHILE LOCATIONS FARTHER NORTH MAY BE SEE ONLY  
SINGLE-DIGIT NEGATIVE ANOMALIES FOR HIGHS. PERIODS OF RAIN AND  
HIGHER ELEVATION SNOW WILL TEND TO BE LIGHT TO MODERATE, BUT A  
SYSTEM ARRIVING LATE IN THE WEEK MAY ENHANCE TOTALS SOMEWHAT OVER  
FAVORED TERRAIN IN THE NORTHWEST. DETAILS OF THIS SYSTEM ARE STILL  
SOMEWHAT UNCERTAIN THOUGH.  
 
BETWEEN THESE TWO REGIMES, THE CENTRAL U.S. WILL SEE PERIODS OF  
RAIN AND THUNDERSTORMS. A LEADING FRONT SHOULD STALL BETWEEN THE  
UPPER MIDWEST AND CENTRAL PLAINS, LIFTING BACK WAS A WARM FRONT  
AHEAD OF A EJECTING FROM THE WEST AFTER MIDWEEK. THIS SYSTEM WILL  
THEN PUSH A NORTH-SOUTH FRONT INTO THE PLAINS, WITH TIMING AND  
WAVE DETAILS OF THE FRONT DEPENDENT ON SPECIFICS OF TRAILING  
DYNAMICS FLOWING THROUGH THE WEST. THESE FRONTS AND THE EJECTING  
WESTERN SYSTEM MAY PRODUCE AT LEAST LOCALIZED AREAS OF SIGNIFICANT  
RAINFALL THAT WOULD BE A RUNOFF THREAT OVER NORTHERN TIER AREAS  
THAT ALREADY HAVE VERY WET SOIL. THE LATE-WEEK SYSTEM REQUIRES  
MONITORING FOR STRONG CONVECTION, WITH DETAILS BECOMING MORE  
EVIDENT IN COMING DAYS.  
 
MOST RAINFALL WITH THE SYSTEM OFF THE EAST COAST SHOULD STAY JUST  
OFFSHORE EARLY IN THE WEEK, BUT IS LIKELY TO EXPAND BACK TO THE  
WEST LATE IN THE WEEK AS THE VERTICALLY STACKED LOW AND WARM FRONT  
TO THE NORTH OF THE SURFACE LOW RETROGRADE BACK TOWARD THE COAST  
AND POSSIBLY A LITTLE INLAND BY NEXT SATURDAY.  
 
RAUSCH/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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