198  
FXUS02 KWBC 051924  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
324 PM EDT FRI JUL 5 2024  
 
VALID 12Z MON JUL 08 2024 - 12Z FRI JUL 12 2024  
 
   
..BERYL LIKELY TO AFFECT TEXAS EARLY NEXT WEEK  
 
   
..DANGEROUS HEAT WAVE IN THE WEST PERSISTS INTO NEXT WEEK  
 
   
..OVERVIEW  
 
THE MOST PROMINENT LARGE SCALE FEATURES DURING THE PERIOD WILL BE A  
PERSISTENT UPPER RIDGE OVER THE WEST SUPPORTING A DANGEROUS AND  
LIKELY RECORD-SETTING HEAT WAVE ACROSS MUCH OF THE REGION INTO NEXT  
WEEK, AND A POSITIVELY TILTED PLAINS/MISSISSIPPI VALLEY/GREAT LAKES  
MEAN TROUGH WHOSE SOUTHERN PERIPHERY MAY INTERACT WITH TROPICAL  
STORM BERYL (FORECAST BY THE NATIONAL HURRICANE CENTER TO  
STRENGTHEN BACK TO HURRICANE STATUS AS IT TRACKS INTO THE WESTERN  
GULF OF MEXICO THIS WEEKEND). BERYL SHOULD BRING A PERIOD OF WINDY  
CONDITIONS AND HEAVY RAINFALL TO PARTS OF TEXAS, WITH POTENTIAL FOR  
NORTHEASTWARD PROGRESSION OF RAINFALL NEXT WEEK. FOR NOW THE  
UNCERTAINTY IN HOW BERYL INTERACTS WITH THE MEAN TROUGH ALOFT IS  
LEADING TO LOWER THAN DESIRED CONFIDENCE REGARDING IMPORTANT  
DETAILS OF THE FORECAST. MEANWHILE, HOT AND HUMID CONDITIONS WILL  
LIKELY CONTINUE FOR MUCH OF THE SOUTHERN STATES AND EXTENDING TO  
THE EAST COAST.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT  
 
LATEST GUIDANCE IS SHOWING SOME SIGNIFICANT TRENDS FOR BERYL, WITH  
A NORTHWARD ADJUSTMENT AS THE SYSTEM REACHES THE WESTERN GULF  
COAST AND THEN GREATER POTENTIAL FOR NORTHEASTWARD RECURVATURE  
THEREAFTER. UPON REACHING EASTERN TEXAS, THE DEGREE OF INTERACTION  
WITH THE MEAN TROUGH ALOFT (AND SHORTWAVE DETAILS WITHIN THE  
TROUGH) WOULD AFFECT THE TRACK AND TIMING OF BERYL'S SURFACE  
REFLECTION. THE PAST COUPLE ICON RUNS HAVE BEEN VERY PROGRESSIVE  
WHILE CMC RUNS STILL SEEM TO BE CATCHING UP FROM BEING ON THE FAR  
LEFT SIDE OF THE ENVELOPE. 00Z MACHINE LEARNING (ML) MODELS  
GENERALLY FAVORED THE RECURVATURE SCENARIO, BETWEEN THE SLOWER 00Z  
ECMWF AND FASTER 00Z/06Z GFS (12Z UKMET LEANING SOMEWHAT FASTER AS  
WELL). EASTWARD AND THEN MUCH FASTER TREND OF THE NEW 12Z ECMWF  
HIGHLIGHTS THE FORECAST UNCERTAINTY. THE UPDATED MANUAL FORECAST  
REFLECTS THIS TREND IN PRINCIPLE WHILE STAYING SOMEWHAT  
CONSERVATIVE WITH DETERMINISTIC QPF GIVEN THE LOWER THAN AVERAGE  
CONFIDENCE FOR THE TIME BEING. CONSULT NATIONAL HURRICANE CENTER  
PRODUCTS FOR THE LATEST INFORMATION REGARDING BERYL.  
 
AS FOR OTHER ASPECTS OF THE FORECAST, THERE IS MODERATE SPREAD  
AMONG THE DYNAMICAL/ML GUIDANCE FOR A TROUGH WITH EMBEDDED LOW  
TRACKING FROM THE NORTHEASTERN PACIFIC INTO WESTERN CANADA MID-LATE  
WEEK WITH NO DOMINANT CLUSTERING FOR THE TIME BEING. THIS FEATURE  
MAY HELP TO PUSH A FRONTAL SYSTEM INTO THE FAR NORTHWESTERN U.S. BY  
LATE NEXT WEEK. A BLENDED/INTERMEDIATE SOLUTION LOOKS LIKE A GOOD  
STARTING POINT HERE. MEANWHILE SOME DIFFERENCES ARISE FOR UPPER  
TROUGH DETAILS FROM EASTERN CANADA INTO THE CENTRAL U.S. BY LATE  
NEXT WEEK. SOME GFS RUNS AND THE NEW 12Z ECMWF SHOW WEAKER  
TROUGHING OVER THE PLAINS/MISSISSIPPI VALLEY BY NEXT FRIDAY VERSUS  
MOST OTHER GUIDANCE, WHILE GUIDANCE IS SPLIT OVER THE DEPTH OF  
TROUGHING OVER SOUTHEASTERN CANADA BY THEN. THE LATTER ISSUE WILL  
AFFECT A SURFACE FRONT LIKELY TO BE NEAR THE EAST COAST LATE NEXT  
WEEK. SOME GUIDANCE SUGGESTS A STRONG ATLANTIC UPPER RIDGING MAY  
BUILD WESTWARD SOMEWHAT AND HELP TO DECELERATE THE EAST COAST  
FRONT.  
 
WITH ADJUSTMENTS TO ACCOUNT FOR THE OFFICIAL TRACK OF BERYL, THE  
UPDATED FORECAST STARTED WITH AN OPERATIONAL MODEL COMPOSITE EARLY  
IN THE PERIOD (MORE ECMWF/GFS EMPHASIS RELATIVE TO THE UKMET/CMC)  
AND THEN TRANSITIONED TOWARD HALF GEFS/ECENS INPUT BY THE END OF  
THE PERIOD NEXT FRIDAY.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS  
 
ONGOING MODEL TRENDS FOR BERYL TEMPER CONFIDENCE IN EXACT DETAILS  
OF MAGNITUDE AND AXIS OF HEAVIEST RAINFALL, WITH SENSITIVITY TO  
BOTH TRACK AND SPEED. CURRENT CONSENSUS WOULD SUGGEST AT LEAST  
SEVERAL INCHES OF RAINFALL IN SOUTH/EAST TEXAS (HIGHER TOTALS WITH  
A SLOWER SPEED OF BERYL) DURING THE FIRST HALF OF NEXT WEEK WITH  
POTENTIAL FOR SOUTHWESTERLY FLOW ALOFT TO SPREAD SOME DEGREE OF  
ENHANCED RAINFALL NORTHEASTWARD FROM TEXAS AFTER MIDWEEK. THE DAYS  
4-5 EXCESSIVE RAINFALL OUTLOOKS FOR MONDAY AND TUESDAY REFLECT  
SLIGHT RISK AREAS WHERE THE RELATIVELY HIGHER POTENTIAL FOR HEAVY  
RAINFALL EXISTS. REFLECTING LATEST MODEL TRENDS, THE DAY 4 SLIGHT  
RISK EXTENDS A LITTLE FARTHER NORTHEASTWARD VERSUS CONTINUITY WHILE  
THE DAY 5 SLIGHT RISK REFLECTS A MORE PRONOUNCED NORTHEASTWARD  
EXTENT. MONDAY'S SLIGHT RISK CONTINUES TO BE A HIGHER-END SLIGHT  
BEFORE INCREASING DIVERGENCE IN GUIDANCE FOR BERYL'S TRACK AND  
ESPECIALLY TIMING. A NEARBY FRONT WILL ALSO PROVIDE A FOCUS FOR  
CONVECTION THAT COULD PRODUCE HEAVY RAINFALL. THERE IS CERTAINLY  
POTENTIAL FOR UPGRADES TO MODERATE RISKS IN FUTURE UPDATES IF  
PLACEMENT OF HIGHER TOTALS COMES INTO BETTER AGREEMENT.  
 
SCATTERED THUNDERSTORMS ARE LIKELY ACROSS THE GULF COAST STATES  
THROUGH MUCH OF NEXT WEEK GIVEN A MOIST AND UNSTABLE AIRMASS IN  
PLACE. ALSO, EARLY IN THE WEEK PARTS OF THE SOUTHEAST WILL LIKELY  
SEE LINGERING ANOMALOUS MOISTURE WITH SUFFICIENT INSTABILITY TO  
SUPPORT SOME LOCALIZED CONVECTION WITH HIGH RAINFALL RATES--  
SUPPORTING ADDITION OF A MARGINAL RISK AREA ON DAY 4 GIVEN SOME  
CARRYOVER OF THE PATTERN FROM THE DAY 3 TIME FRAME. FARTHER NORTH,  
THE UPPER TROUGH PUSHING ONE OR MORE COLD FRONTS THROUGH THE  
NORTH-CENTRAL TO NORTHEASTERN U.S. ALSO WILL LEAD TO SOME STORMS,  
WITH THE BULK OF THE ACTIVITY MOVING EAST WITH TIME FROM THE  
MIDWEST/GREAT LAKES MONDAY TOWARD THE EASTERN U.S. TUESDAY-  
THURSDAY. SOME FOCUS OF THE CONVECTIVE RAIN AND SUFFICIENT  
INSTABILITY FOR HEAVY RAIN RATES IN MUCH OF NEW YORK AND  
PENNSYLVANIA HAVE PROMPTED A MARGINAL RISK IN THE ERO FOR DAY  
5/TUESDAY. MEANWHILE, BY TUESDAY AND BEYOND, SOME MOISTURE MAY FEED  
INTO THE FOUR CORNERS STATES IN A MONSOONAL PATTERN, WARRANTING A  
MARGINAL RISK FOR DAY 5/TUESDAY MAINLY FOR NEW MEXICO--ESPECIALLY  
CONSIDERING SENSITIVITIES DUE TO BURN SCARS AND AREAS THAT HAVE  
SEEN AMPLE RAINFALL RECENTLY.  
 
THE WEST WILL CONTINUE TO SEE A MAJOR TO EXTREME AND LONG-LIVED  
HEAT WAVE INTO NEXT WEEK. HIGHS EXCEEDING 110F SHOULD BE WIDESPREAD  
IN THE DESERT SOUTHWEST, WITH TYPICALLY HOTTER LOCATIONS EXCEEDING  
120F. FARTHER NORTH, HIGHS INTO THE 100S ARE FORECAST INTO OREGON  
AND WASHINGTON AND EAST INTO THE INTERMOUNTAIN WEST, AS  
TEMPERATURES SOAR 10-20F ABOVE NORMAL WITH LOCALLY HIGHER  
ANOMALIES. NUMEROUS DAILY RECORDS ARE LIKELY TO BE BROKEN DURING  
THIS HEAT WAVE, WITH MONTHLY RECORDS NOT OUT OF THE QUESTION. THE  
PROLONGED NATURE OF THE HEAT WAVE AND RECORD WARM OVERNIGHT  
TEMPERATURES WILL INCREASE HEAT STRESS. MEANWHILE, WARMER THAN  
AVERAGE TEMPERATURES IN THE NORTHEAST EARLY IN THE WEEK SHOULD  
MODERATE BY MIDWEEK. THE SOUTHEAST SHOULD SEE NEAR NORMAL HEAT FOR  
THIS TIME OF YEAR--WHICH IS STILL HOT AND HUMID. THE SOUTH-CENTRAL  
U.S. SHOULD SEE SOME MINOR HEAT RELIEF WITH BELOW AVERAGE  
TEMPERATURES GIVEN THE CLOUDS AND RAIN CHANCES.  
 
RAUSCH/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 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  
 
 
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