388  
FXUS02 KWBC 140659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT FRI JUN 14 2024  
 
VALID 12Z MON JUN 17 2024 - 12Z FRI JUN 21 2024  
   
..EARLY SEASON HEAT WAVE FROM THE MIDWEST TO THE EAST COAST
 
 
...HEAVY RAINFALL THREAT ALONG THE CENTRAL-WESTERN GULF COAST AND  
PARTS OF THE NORTHERN TIER...  
   
..OVERVIEW
 
 
A STRONG UPPER RIDGE FORECAST TO BUILD OVER PARTS OF THE EAST  
WILL LIKELY SUPPORT A BROAD AREA OF HOT AND DRY WEATHER NEXT WEEK,  
WITH THE GREATEST ANOMALIES AND POTENTIAL FOR DAILY RECORDS  
EXTENDING FROM THE OHIO VALLEY/LOWER GREAT LAKES INTO THE NORTHERN  
MID-ATLANTIC/NORTHEAST. MEANWHILE STRONG DYNAMICS EJECTING FROM THE  
NORTHWEST AND ASSOCIATED SURFACE DEVELOPMENT/FRONTS EARLY IN THE  
WEEK SHOULD PRODUCE ONE OR MORE AREAS OF SIGNIFICANT PRECIPITATION  
BETWEEN THE NORTHERN ROCKIES AND MIDWEST. THE LINGERING WESTERN  
U.S. MEAN TROUGH ALOFT MAY RETROGRADE TO THE WEST COAST BY LATE IN  
THE WEEK. BENEATH THE UPPER RIDGE THAT SHOULD EXTEND BACK TO THE  
SOUTHERN PLAINS/ROCKIES BY THE LATTER HALF OF THE WEEK, THE  
COMBINATION OF UPPER LEVEL IMPULSES AND ABUNDANT DEEP MOISTURE WILL  
BRING A POTENTIAL FOR AREAS OF HEAVY RAIN ALONG AND NEAR THE  
WESTERN HALF OF THE GULF COAST.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
EARLY IN THE PERIOD, THE PRIMARY GUIDANCE DIFFERENCE OF NOTE IS  
THAT LATEST GFS RUNS ARE A BIT ON THE SLOW SIDE VERSUS MOST OTHER  
SOLUTIONS WITH THE STRONG UPPER SYSTEM CROSSING THE NORTHWEST  
DURING MONDAY-TUESDAY. THIS RESULTS IN THE MODEL PULLING ITS HEAVY  
QPF AXIS FARTHER WEST THAN CONSENSUS IN THE VICINITY OF THE  
NORTHERN ROCKIES.  
 
MEANWHILE GUIDANCE AGREES THAT THE CENTER OF THE STRENGTHENING  
EASTERN U.S. UPPER RIDGE SHOULD TRACE A PATH FROM NEAR THE WESTERN  
CAROLINAS EARLY MONDAY INTO THE NORTHERN MID-ATLANTIC/SOUTHERN NEW  
ENGLAND BY EARLY WEDNESDAY. THEN CONSENSUS SHOWS EXPANSION OF UPPER  
RIDGING BACK INTO THE SOUTHERN HALF OF THE PLAINS/SOUTHERN ROCKIES  
BUT WITH INCREASING SPREAD FOR WHERE THE STRONGEST PART OF THE  
RIDGE WILL BE (RANGING BETWEEN THE OHIO VALLEY AND WESTERN ATLANTIC  
BY FRIDAY). MOST OF THE 12Z ECMWF-INITIALIZED MACHINE LEARNING (ML)  
MODELS SHOW THE UPPER HIGH OVER OR A LITTLE SOUTH OF THE 12Z ECMWF  
MEAN LOCATION OVER THE EAST AS OF EARLY NEXT FRIDAY WHILE THE NEW  
00Z GFS/CMC HAVE IT OVER THE WESTERN ATLANTIC. THE MEAN TROUGH OVER  
THE WEST SHOULD WEAKEN AND RETROGRADE A BIT MID-LATE WEEK AS THE  
UPPER RIDGE EXPANDS, WITH LOW PREDICTABILITY FOR SHORTWAVE DETAILS  
AFTER THE VIGOROUS EARLY WEEK SYSTEM EJECTS. BY NEXT FRIDAY THE ML  
MODELS SUPPORT A SOLUTION CLOSEST TO THE GEFS/ECENS MEANS, SHOWING  
A LITTLE BETTER DEFINITION FOR THE WEST COAST TROUGH THAN SOME OF  
THE 12Z/18Z DYNAMICAL MODEL RUNS. PREDICTABILITY IS TYPICALLY  
FAIRLY LOW FOR THE UPPER IMPULSES RETROGRADING UNDERNEATH THE  
RIDGE, AND WHILE THERE IS A FAIRLY GOOD CONSENSUS FOR THE AREA OF  
ENHANCED DEEP MOISTURE RETROGRADING ACROSS THE WESTERN HALF OF THE  
GULF OF MEXICO/GULF COAST, QPF SOLUTIONS ARE MUCH MORE DIVERSE.  
 
THE UPDATED FORECAST BLEND BASED ON 12Z/18Z GUIDANCE STARTED WITH  
AN OPERATIONAL MODEL COMPOSITE FOR THE FIRST HALF OF THE PERIOD  
FOLLOWED BY GRADUALLY INCREASING 18Z GEFS/12Z ECENS MEAN WEIGHT SO  
THAT THE MEANS WERE 60 PERCENT OF THE BLEND BY THE END OF THE  
FORECAST NEXT FRIDAY.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
STRONG DYNAMICS EJECTING FROM THE NORTHWEST WILL PROMOTE PLAINS  
SURFACE DEVELOPMENT (ULTIMATELY TRACKING INTO CANADA) DURING THE  
FIRST PART OF THE WEEK. FROM MONDAY INTO EARLY TUESDAY, A LEADING  
NORTHERN TIER FRONT WILL LIKELY STALL AHEAD OF THE EVOLVING SURFACE  
WAVE, WITH GUIDANCE SHOWING A FAIRLY STEADY AREA OF ANOMALOUS  
MOISTURE OVER THE UPPER MIDWEST. WHILE THERE IS STILL SOME  
MODEL/ENSEMBLE SPREAD FOR THE AXIS OF HEAVIEST RAINFALL, THE SETUP  
LOOKS FAVORABLE ENOUGH TO INTRODUCE A SLIGHT RISK AREA IN THE DAY 4  
EXCESSIVE RAINFALL OUTLOOK. THE PROPOSED LOCATION OVER NORTHERN-  
CENTRAL MINNESOTA AND SOME NEARBY AREAS REPRESENTS AN INTERMEDIATE  
APPROACH AMONG THE CURRENT GUIDANCE SPREAD. MEANWHILE THERE IS A  
MARGINAL RISK ACROSS MUCH OF MONTANA WHERE THE UPPER SYSTEM MAY  
PRODUCE SOME AREAS OF HEAVY RAINFALL--WITH SOME SNOW ALSO POSSIBLE  
IN HIGHEST ELEVATIONS OF THE NORTHERN ROCKIES.  
 
BY THE DAY 5 TIME FRAME TUESDAY/TUESDAY NIGHT, EXPECT CENTRAL U.S.  
CONVECTION TO START EXPANDING SOUTHWARD ALONG THE COLD FRONT  
ANCHORED BY THE SURFACE WAVE TRACKING INTO CANADA. CURRENTLY THERE  
IS ENOUGH SPREAD TO WARRANT ONLY A MARGINAL RISK AREA FROM THE  
UPPER MIDWEST INTO THE CENTRAL PLAINS BUT IMPROVED CLUSTERING IN  
THE NEAR FUTURE WOULD MERIT ONE OR MORE EMBEDDED SLIGHT RISK AREAS.  
A LINGERING MARGINAL RISK AREA IS ALSO IN PLACE OVER NORTHEASTERN  
MONTANA/NORTHWESTERN NORTH DAKOTA NEAR THE PATH OF THE UPPER  
SYSTEM.  
 
GUIDANCE GENERALLY AGREES THAT AN AREA OF DEEP TROPICAL MOISTURE  
SHOULD SHIFT WESTWARD ACROSS THE WESTERN HALF OF THE GULF OF  
MEXICO, BRINGING A POTENTIAL FOR SOME HEAVY RAINFALL TO LOCATIONS  
ALONG THE CENTRAL AND WESTERN GULF COAST NEXT WEEK. OPERATIONAL  
MODELS DIFFER CONSIDERABLY FOR QPF DETAILS WITH ENSEMBLE  
PROBABILITIES ALSO SOMEWHAT DIFFUSE, WHILE ML MODELS SHOW A BIT  
MORE COHERENCE FOR RAIN POTENTIAL ALONG THE LOUISIANA AND EASTERN  
TEXAS COASTS. FOR NOW PREFER TO MAINTAIN A MARGINAL RISK FOR DAYS  
4-5 WHILE AWAITING BETTER AGREEMENT REGARDING QPF SIGNALS.  
 
THE STRONG UPPER RIDGE BUILDING OVER THE EAST NEXT WEEK WILL TEND  
TO PRODUCE THE GREATEST TEMPERATURE ANOMALIES FROM THE MIDWEST AND  
OHIO VALLEY/LOWER GREAT LAKES INTO THE NORTHERN MID-ATLANTIC AND  
NORTHEAST, WITH MULTIPLE DAYS OF READINGS 10-20F ABOVE NORMAL. THIS  
WOULD TRANSLATE TO HIGHS WELL INTO THE 90S, ALONG WITH LOWS IN THE  
UPPER 60S TO UPPER 70S PROVIDING LITTLE OVERNIGHT HEAT RELIEF.  
DAILY RECORDS WILL BE POSSIBLE WITHIN THE ABOVE AREAS. THIS HEAT  
WAVE WILL LIKELY EXTEND BEYOND FRIDAY. WHILE THE PATTERN DETAILS  
WERE OBVIOUSLY DIFFERENT, THE AXIS OF GREATEST TEMPERATURE  
ANOMALIES HAS SOME SIMILARITY TO THE 1994 HEAT WAVE THAT WAS  
OBSERVED AROUND THE SAME PART OF JUNE. IN CONTRAST TO THE EASTERN  
HEAT, THE DEEP UPPER TROUGH CROSSING THE NORTHWEST EARLY NEXT WEEK  
WILL BRING A COUPLE DAYS OF HIGHS 10-20F BELOW NORMAL TO PARTS OF  
THE WEST AND NORTHERN HIGH PLAINS. AFTER THIS SYSTEM DEPARTS,  
EXPECT THE WEST TO TREND WARMER, REACHING ABOVE NORMAL BY LATE  
WEEK. MOIST EASTERLY FLOW SHOULD BRING A COOLER TREND TO THE  
SOUTHERN HIGH PLAINS BY LATE WEEK.  
 
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 FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page