712  
FXUS02 KWBC 090701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT MON MAY 09 2022  
 
VALID 12Z THU MAY 12 2022 - 12Z MON MAY 16 2022  
 
...BLOCKY PATTERN THROUGH LATE 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 RAINFALL FOCUS TO THE CAROLINAS...  
   
..OVERVIEW
 
 
THE START OF THE PERIOD WILL FEATURE A MEAN TROUGH ALOFT OVER THE  
WEST, RIDGING THAT EXTENDS FROM THE SOUTHERN PLAINS THROUGH GREAT  
LAKES/NORTHEAST, AND AN UPPER LOW OFF THE SOUTHEAST COAST.  
TEMPERATURES WILL LIKELY CHALLENGE DAILY RECORDS UNDER AND NEAR  
THE UPPER RIDGE AXIS LATE THIS WEEK WHILE PARTS OF THE WEST WILL  
SEE CHILLY WEATHER WITH RAIN AND HIGHER ELEVATION SNOW. BETWEEN  
THESE REGIMES, A STORM SYSTEM EMERGING OVER THE NORTHERN PLAINS  
MAY PRODUCE SOME AREAS OF HEAVY RAINFALL WHERE WET GROUND  
CONDITIONS ALREADY EXIST. THEN DURING THE WEEKEND AND EARLY NEXT  
WEEK MOST GUIDANCE SHOWS THE PATTERN TRANSITIONING TOWARD A  
WESTERN RIDGE/EAST-CENTRAL U.S. TROUGH CONFIGURATION. THIS  
EVOLUTION SHOULD FINALLY PUSH THE RAINFALL FOCUS TO THE EAST OF  
THE PLAINS. THE INITIAL UPPER LOW TRACKING INTO THE SOUTHEAST  
AROUND FRIDAY DUE TO A RETROGRADING ATLANTIC RIDGE SHOULD QUICKLY  
LIFT NORTHWARD AND OPEN UP DURING THE WEEKEND, WITH ASSOCIATED  
RAINFALL SPREADING INTO AND NORTH FROM THE CAROLINAS. THE RIDGE  
BUILDING OVER THE WEST WILL LEAD TO INCREASING COVERAGE OF VERY  
WARM TO HOT TEMPERATURES OVER THE SOUTHERN HALF OF THE WEST DURING  
SATURDAY-MONDAY.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
BASED ON GUIDANCE AVAILABLE THROUGH THE 12Z/18Z CYCLES, THE 18Z  
GFS AND 12Z ECMWF/CMC PROVIDED THE MOST COMPATIBLE AND CONSISTENT  
CLUSTER FOR THE OVERALL FORECAST THROUGH THE PERIOD ALONG WITH  
REASONABLE SUPPORT FROM THE ENSEMBLE MEANS. THE STARTING BLEND  
USED THOSE THREE OPERATIONAL RUNS FOR ABOUT THE FIRST HALF OF THE  
PERIOD AND ADDED IN A MODERATE WEIGHT OF 18Z GEFS/12Z ECMWF MEANS  
THEREAFTER.  
 
GFS/ECMWF CONTINUITY AND TRENDS OF OTHER GUIDANCE STILL SEEM TO BE  
POINTING MORE TOWARD SOME VARIATION OF A GFS/ECMWF SCENARIO FOR  
THE VIGOROUS SYSTEM EXPECTED TO EMERGE FROM THE WEST AND TRACK  
OVER THE NORTHERN PLAINS INTO SOUTHERN CANADA LATE THIS WEEK.  
ASIDE FROM SOME DETAIL VARIABILITY, GFS/ECMWF RUNS CONVERGED  
FAIRLY WELL OVER THE PAST DAY OR SO WHILE THE PREVIOUSLY FAST CMC  
HAS BEEN GRAVITATING IN THEIR DIRECTION. UKMET RUNS HAD BEEN THE  
MOST EXTREME WITH A SOUTHERN TRACK OF THE WESTERN UPPER LOW/TROUGH  
BUT THE NEW 00Z RUN IS FINALLY TRENDING IN A FAVORABLE DIRECTION.  
 
BEHIND THIS SYSTEM, MODELS AND ENSEMBLES STILL SHOW A MODERATE  
AMOUNT OF SPREAD FOR THE CHARACTER OF TRAILING ENERGY THAT  
CONSENSUS SHOWS FLOWING THROUGH THE NORTHWEST AND THEN SHARPENING  
OVER THE PLAINS AND EAST-CENTRAL U.S. WHILE RIDGING BUILDS INTO  
THE WEST. THE FAVORED MODEL CLUSTER MENTIONED ABOVE FIT WELL  
WITHIN THE ENSEMBLE MEAN TEMPLATE BUT THE NEW 00Z CYCLE HAS  
INTRODUCED MORE SPREAD IN OPPOSING DIRECTIONS, AS THE GFS HAS  
TRENDED FLATTER WITH THE TROUGH (DUE TO STRONGER DEPICTION OF  
SHORTWAVE ENERGY REACHING THE WEST BY MONDAY) WHILE THE CMC FORMS  
A CLOSED LOW FARTHER SOUTH THAN OTHER GUIDANCE.  
 
FINALLY, LATEST TRENDS FOR THE UPPER LOW REACHING THE SOUTHEAST  
COAST AROUND EARLY FRIDAY HAVE BEEN TOWARD FASTER NORTHWARD  
PROGRESSION AFTER THAT TIME ALONG WITH OPENING OF THE LOW BY LATE  
SATURDAY.  
   
..WEATHER/THREAT HIGHLIGHTS
 
 
THE STRONG UPPER RIDGE EXTENDING FROM THE SOUTHERN PLAINS THROUGH  
THE GREAT LAKES/NORTHEAST AS OF THURSDAY WILL PROMOTE MUCH ABOVE  
NORMAL TEMPERATURES FROM MUCH OF THE PLAINS AND MISSISSIPPI VALLEY  
THROUGH THE GREAT LAKES AND NORTHEAST LATE THIS WEEK.  
HIGHS/MORNING LOWS WILL BE AT LEAST 10-20F ABOVE NORMAL WITH SOME  
EMBEDDED PLUS 20-25F ANOMALIES POSSIBLE FROM THE CENTRAL PLAINS  
INTO GREAT LAKES, AND LOCATIONS ACROSS A FAIRLY BROAD AREA MAY  
CHALLENGE DAILY RECORDS. AFTER FRIDAY EXPECT THE ABOVE NORMAL  
TEMPERATURES TO BE MORE CONFINED TO THE GREAT LAKES/NORTHEAST AND  
THE FAR SOUTHERN PLAINS/WESTERN GULF COAST REGION. THERE WILL BE  
A LINGERING POTENTIAL FOR DAILY RECORDS OVER THE NORTHEAST INTO  
SATURDAY AND OVER EASTERN TEXAS AND VICINITY THROUGH THE END OF  
THE PERIOD.  
 
THE FRONTAL SYSTEM AND UPPER DYNAMICS CROSSING THE NORTHWEST LATE  
THIS WEEK WILL PRODUCE A BRIEF PERIOD OF ENHANCED RAIN AND HIGH  
ELEVATION SNOW AS WELL AS HIGHS 5-15F BELOW NORMAL. MEANWHILE THE  
SOUTHERN PART OF THE WEST SHOULD MODERATE TO SLIGHTLY ABOVE NORMAL  
BY FRIDAY. THEN ARRIVAL OF THE UPPER RIDGE WILL EXTEND THE  
WARMING TREND OVER THE WEST THROUGH THE WEEKEND. HIGHS OF 10-20F  
ABOVE NORMAL SHOULD EXPAND FROM CALIFORNIA EASTWARD FROM SATURDAY  
ONWARD AND SOME LOCATIONS COULD REACH RECORD HIGHS BY  
SUNDAY-MONDAY. NORTHERN AREAS OF THE WEST SHOULD BE CLOSER TO  
NORMAL AND ONE OR MORE FRONTS MAY PRODUCE PERIODS OF LIGHT TO  
MODERATE PRECIPITATION OVER THE PACIFIC NORTHWEST.  
 
LATE THIS WEEK THE SYSTEM EMERGING FROM THE WEST AND DEVELOPING  
OVER THE NORTHERN PLAINS BEFORE TRACKING INTO SOUTHERN CANADA,  
ALONG WITH ASSOCIATED FRONTS, MAY PRODUCE AREAS OF HEAVY RAINFALL  
OVER PARTS OF THE FAR NORTHERN TIER WHERE SOME AREAS ARE QUITE  
SENSITIVE TO ADDED RAIN DUE TO VERY WET GROUND CONDITIONS. THE  
EXPERIMENTAL DAY 4 (THURSDAY-THURSDAY NIGHT) EXCESSIVE RAINFALL  
OUTLOOK HAS INTRODUCED A SLIGHT RISK AREA OVER PARTS OF NORTHERN  
NORTH DAKOTA AND MINNESOTA WHERE THERE IS THE BEST OVERLAP OF  
GUIDANCE SIGNALS FOR SIGNIFICANT RAIN AND INSTABILITY, ALONG WITH  
HIGH SOIL MOISTURE. DEPENDING ON SYSTEM EVOLUTION, AREAS FARTHER  
WEST BACK TO THE NORTHERN HIGH PLAINS COULD ALSO SEE SIGNIFICANT  
RAINFALL. SOME LOCALLY MODERATE TO HEAVY SHOWERS AND  
THUNDERSTORMS WILL BE POSSIBLE FARTHER SOUTH ALONG THE WAVY  
TRAILING FRONT (WHICH MAY HANG UP FOR ABOUT A DAY AS WESTERN  
ENERGY CATCHES UP TO IT) BUT SO FAR WITH LESS AGREEMENT FOR  
SPECIFICS. THE STORM PREDICTION CENTER IS ALSO MONITORING THE  
POTENTIAL FOR SEVERE WEATHER, SO CHECK THE LATEST OUTLOOKS FOR  
UPDATED INFORMATION. RAINFALL AND THE FOCUSING FRONT SHOULD  
BECOME MORE PROGRESSIVE FROM SATURDAY ONWARD, LEADING TO A DRIER  
TREND OVER THE PLAINS. RETROGRESSION OF THE WESTERN ATLANTIC  
UPPER LOW INTO THE SOUTHEAST TOWARD THE END OF THE WEEK SHOULD  
SPREAD RAIN INTO THE CAROLINAS AND VICINITY BY AROUND FRIDAY WITH  
SOME OF THIS MOISTURE SPREADING NORTHWARD THEREAFTER. HIGHEST  
TOTALS SHOULD BE OVER OR NEAR THE EASTERN CAROLINAS. AMOUNTS  
FARTHER NORTH SHOULD TREND LIGHTER DUE TO DECREASING FOCUS OF  
MOISTURE AS THE UPPER LOW OPENS UP WHILE IT LIFTS NORTHWARD.  
 
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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