173  
FXUS02 KWBC 071850  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
249 PM 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 AND AN EMERGING ONSHORE  
RAINS FOCUS TO THE CAROLINAS...  
 
   
..OVERVIEW
 
 
IT REMAINS THE CASE THAT GUIDANCE SHOWS 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
 
 
GUIDANCE DIFFERENCES IN THE FORECAST ARE MAINLY WITH FEATURES  
WITHIN THE WESTERN MEAN TROUGH, WITH VARYING IDEAS FOR THE  
COMBINATION OF A SHARPER 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 AND ESPECIALLY THE CMC HAVE BEEN ON THE  
FASTER SIDE OF THE ENVELOPE WITH EJECTION OF THE LEADING SYSTEM.  
ECMWF RUNS HAVE BEEN SLOWER, BUT HAS BEEN GRADUALLY TRENDING  
FASTER IN RECENT RUNS DUE TO TRENDING FASTER WITH THE TRAILING  
FLOW. RECENT UKMET RUNS HAVE BEEN THE SLOWEST TO BRING IN THE  
UPSTREAM TROUGHING, LEADING TO SLOW PROGRESSION OF THE LEADING  
FEATURE AND A RATHER FAR SOUTH TRACK OF THE UPPER LOW BY LATE  
THURSDAY. 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.  
 
OVERALL, THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED  
FROM A BLEND OF THE NEAR MIDDLE OF THE FORECAST ENVELOPE CLUSTER  
OF THE 06 UTC GFS/GEFS MEAN, 00 UTC ECMWF/ECMWF ENSEMBLE MEAN, WPC  
CONTINUITY AND THE 13 UTC NATIONAL BLEND OF MODELS. LATEST 12 UTC  
GUIDANCE TRENDS GENERALLY REMAIN IN LINE.  
 
IN THE EAST, 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 THE AFOREMENTIONED  
CONSENSUS APPROACH ALSO OFFERING A REASONABLE STARTING POINT AND  
DECENT CONTINUITY. HOWEVER, A MANUAL ADJUSTMENT WAS APPLIED TO  
LIMIT SOME NORTHWARD EXPANSION OF ORGANIZED QPF HEADING INTO NEXT  
WEEKEND CONSIDERING A SOUTHWARD CLOSED LOW TREND.  
 
   
..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 NEXT WEEK, BUT IS LIKELY TO EXPAND BACK TO THE WEST  
AND LEAD TO SOME MODERATE AMOUNTS LATE NEXT WEEK AS THE VERTICALLY  
STACKED LOW AND WARM FRONT TO THE NORTH OF THE SURFACE LOW  
RETROGRADE BACK TOWARD THE COAST AND INLAND INTO NEXT SATURDAY.  
 
SCHICHTEL/RAUSCH  
 
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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