595   
FXUS02 KWBC 311900  
PMDEPD  
  
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SAT AUG 31 2024  
  
VALID 12Z TUE SEP 03 2024 - 12Z SAT SEP 07 2024  
  
   
..OVERVIEW  
  
A FAIRLY PROGRESSIVE NORTHERN STREAM UPPER LEVEL PATTERN WILL BE   
IN PLACE NEXT WEEK DURING THE MEDIUM RANGE PERIOD. ON THE LARGE   
SCALE, UPPER RIDGING ACROSS THE SOUTHERN U.S. WILL EXPAND AND BUILD  
INTO THE WEST AS SYSTEMS RIDE THE TOP OF THE RIDGE FROM WEST TO   
EAST, EVENTUALLY BUILDING A DEEPENING TROUGH OVER THE GREAT LAKES   
TO NORTHEAST MID TO LATE NEXT WEEK. THIS PATTERN SHOULD PUSH A   
COUPLE OF FRONTAL BOUNDARIES INTO THE CENTRAL AND SOUTHEASTERN   
U.S., WITH PERIODS OF STORMY WEATHER EXPECTED TO ACCOMPANY THEM.   
MEANWHILE, EMBEDDED ENERGY WITHIN THE LARGER SCALE UPPER RIDGE AND   
A PERSISTENT SURFACE TROUGH AND EMBEDDED WAVES NEAR THE GULF COAST   
SHOULD PROVIDE FOCUS FOR HEAVY RAINFALL FROM TEXAS TO THE LOWER   
MISSISSIPPI VALLEY AND GULF COAST.  
  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT  
  
MODELS ARE IN REASONABLE AGREEMENT WITH RESPECT TO THE OVERALL  
SYNOPTIC EVOLUTION ACROSS THE CONUS DURING THE MEDIUM RANGE   
PERIOD. THE 00Z EURO CLUSTERS REASONABLY WELL WITH THE ML MODELS   
AND 00Z CMC/UKMET/ECE/CMCE AND 06Z GEFS. THE DETERMINISTIC GFS  
TRENDED DRIER AND MORE SUPPRESSED WITH QPF ALONG THE GULF COAST,  
LOWER MISSISSIPPI VALLEY AND TENNESSEE VALLEY THROUGHOUT THE   
PERIOD. THE 00Z EUROPEAN SUITE WAS FAVORED IN THE MEDIUM RANGE  
BLEND FOR THOSE REASONS.   
  
THE DAY 3 BLEND CONSISTS OF THE 00Z  
ECMWF/CMC/UKMET AND 06 GFS WITH WEIGHTING TILTED TOWARD THE  
OPERATIONAL EURO AND GFS. THE EURO EMERGES A FAVORITE IN THE BLEND  
ON DAY 4 AT THE EXPENSE OF THE GFS WHICH BEGINS TO SPLIT FLOW OVER  
THE EASTERN U.S./CANADA. THE ENSEMBLES FILTER INTO THE BLEND ON DAY  
5 AND ARE FAVORED THROUGH DAY 7.  
  
   
..WEATHER/HAZARDS HIGHLIGHTS  
  
THE MAIN HEAVY RAINFALL FOCUS DURING THE PERIOD WILL BE ACROSS THE  
SOUTH AS SHORTWAVE ENERGY MOVES INLAND FROM THE WESTERN GULF AND A  
SURFACE FRONT LINGERS ALONG/NEAR THE COAST. PRECIPITATION COVERAGE  
AND TOTALS REMAIN HIGHLY UNCERTAIN, BUT THE OVERALL DYNAMICS AND   
ANOMALOUS MOISTURE SUPPORT A HEAVY TO EXCESSIVE RAINFALL THREAT   
WITH SLOW- MOVING STORMS. THIS IS COVERED BY FAIRLY BROAD MARGINAL   
RISKS ON THE DAYS 4 AND 5 EROS (COVERING TUESDAY TO WEDNESDAY   
NIGHT), WITH A POSSIBLE FOCUS ACROSS THE GULF COAST AND FARTHER   
INLAND ACROSS MUCH OF TEXAS TUESDAY, SPREADING EASTWARD WITH TIME   
INTO THE LOWER MISSISSIPPI VALLEY. FOR MIDWEEK AND BEYOND, THE   
LINGERING FRONTAL BOUNDARY ACROSS THE SOUTH WILL PROMOTE ADDITIONAL  
RAIN AND LOCALLY HEAVY DOWNPOURS. AMOUNTS AND LOCATIONS REMAIN   
VERY UNCERTAIN, BUT THE TREND IS FOR INCREASED RAIN TOTALS ALONG   
THE GULF COAST AND INTO PARTS OF THE SOUTHEAST. EVENTUALLY BY LATE   
WEEK, SOME MOISTURE MAY SPREAD INTO THE OHIO VALLEY AND/OR EASTERN   
SEABOARD. MEANWHILE, SOME LIGHT TO MODEST PRECIPITATION SHOULD   
ACCOMPANY A SHORTWAVE MOVING THROUGH THE INTERIOR WEST, AND RAIN   
CHANCES COULD SPREAD INTO THE NORTHERN PLAINS AND MIDWEST/GREAT   
LAKES LATER NEXT WEEK ALONG AND AHEAD OF THE NORTHERN FRONT.  
  
MODESTLY ABOVE NORMAL TEMPERATURES ACROSS THE NORTHERN PLAINS ON   
TUESDAY SHOULD SHIFT EAST AND MODERATE. MEANWHILE, INCREASING HEAT   
IS EXPECTED ACROSS MUCH OF THE WEST, WITH MODERATE TO MAJOR   
HEATRISK THREATS ACROSS THE SOUTHWEST AND CENTRAL VALLEYS OF   
CALIFORNIA. FROM THE SOUTHERN PLAINS TO THE MIDWEST AND THE EAST,   
TEMPERATURES SHOULD BE NEAR OR BELOW NORMAL FOR THIS TIME OF THE   
YEAR WITHIN A RATHER PLEASANT AIR MASS THROUGH MUCH OF NEXT WEEK.  
  
KEBEDE/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 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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