083
FXUS02 KWBC 060705
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 AM EDT WED AUG 6 2025
VALID 12Z SAT AUG 09 2025 - 12Z WED AUG 13 2025
...MAJOR HEAT THREAT FOCUS SHIFTS FROM THE SOUTHWEST AND SOUTH-
CENTRAL PLAINS TO THE MIDWEST/GREAT LAKES/NORTHEAST THIS PERIOD...
..SOUTHEAST U.S. COASTAL LOW BEING MONITORED BY THE NHC
..OVERVIEW
DYNAMIC MEAN UPPER TROUGHING WILL GRADUALLY WORK EAST ACROSS THE
NORTHERN U.S., DRIVING STRONG TO SEVERE THUNDERSTORM CHANCES FROM
THE NORTH-CENTRAL PLAINS TO THE MIDWEST/GREAT LAKES. A WAVY
FRONTAL BOUNDARY WILL LINGER ALONG THE GULF AND SOUTHEAST COASTS,
RESULTING IN UNSETTLED WET WEATHER FOR PORTIONS OF THE
SOUTHEAST/FLORIDA AND SOUTHERN MID-ATLANTIC AS NHC MONITORS A
COASTAL LOW FOR POTENTIAL TROPICAL DEVELOPMENT. MEANWHILE, AN
EXPANDING UPPER RIDGE WILL SPREAD A HEATWAVE FROM THE SOUTHWEST
AND SOUTH-CENTRAL PLAINS TO THE MIDWEST/GREAT LAKES/NORTHEAST THIS
WEEKEND INTO NEXT WEEK. THERE MAY ALSO BE AN UPTICK IN MONSOONAL
MOISTURE FLOW INTO THE SOUTHWEST/SOUTHERN ROCKIES BY THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT GUIDANCE CONTINUES TO SHOW REALLY GOOD AGREEMENT ON THE
UPPER LEVEL PATTERN THROUGH THE PERIOD, RESULTING IN ABOVE AVERAGE
FORECAST CONFIDENCE. ALL AVAILABLE GUIDANCE IS CAPTURING THE
SYNOPTIC PATTERN WELL, WITH STRONG UPPER RIDGING THAT HAS ANCHORED
OVER THE SOUTHWEST EXPANDING HEAT RISKS THROUGH THE SOUTH-CENTRAL
PLAINS TO THE MIDWEST/GREAT LAKES/NORTHEAST IN ADVANCE OF A DEEP
TROUGH AND LEAD SURFACE FRONTAL SYSTEM SLATED TO MOVE SLOWLY
EASTWARD OVER THE NORTHERN U.S. WITH SEVERAL EMBEDDED SHORTWAVES.
HOWEVER, THERE IS SOME UNCERTAINTY IN THE DETAILS OF THE SENSIBLE
WEATHER AT THE SURFACE, WITH SOME DIFFERENCES IN PRECIPITATION
AMOUNTS AND LOCATIONS. OVERALL, THE GENERAL CONSENSUS IS FOR THE
HEAVIEST RAIN TO FOCUS OVER THE NORTH-CENTRAL PLAINS/UPPER MIDWEST
AND FROM THE SOUTHEAST COAST/FLORIDA TO THE SOUTHERN MID-ATLANTIC.
IN THE SOUTHEAST AND EASTERN GULF/FLORIDA, PRECIPITATION INTENSITY
AND LOCATION IS ALSO PENDING ANY FRONTAL WAVE OR TROPICAL
DEVELOPMENT. GUIDANCE HAS VARIED WITH THE SYSTEM AND QPF FOCUS.
THE WPC MEDIUM-RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A
COMPOSITE OF COMPATIBLE GFS/ECMWF/UKMET/CANADIAN FEATURES FOR THE
WEEKEND ALONG WITH WPC CONTINUITY AND THE NATIONAL BLEND OF MODELS
(NBM). OPTED TO INCREASINGLY SWITCH TO BETTER CLUSTERED GUIDANCE OF
THE GEFS/ECMWF/CANADIAN ENSEMBLE MEANS THROUGH EARLY-MID NEXT WEEK
AMID SLOWLY GROWING FORECAST SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
A SLOW TO DISLODGE COOLED HIGH PRESSURE AIRMASS WILL LINGER OVER
PORTIONS OF THE EASTERN U.S. WEEKEND, FURTHER MODERATING NEXT
WEEK. HIGH MOISTURE CONTENT AND INSTABILITY NEAR A FRONT ON THE
LEADING EDGE OF THIS AIRMASS WILL FOCUS SOME LOCALIZED HEAVY RAIN
OVER THE COASTAL SOUTHEAST/FLORIDA, WHICH MAY RAISE FLASH FLOODING
RISKS GIVEN WET ANTECEDENT CONDITIONS. WPC'S EXCESSIVE RAINFALL
OUTLOOK (ERO) DEPICTS MARGINAL RISK AREAS FOR DAY 4/SATURDAY AND
DAY 5/SUNDAY. THIS AREA IS QUITE UNCERTAIN WITH HOW THE FRONT AND
COASTAL WAVE/LOW WILL EVOLVE, AND NHC IS MONITORING THIS AREA FOR
POTENTIAL TROPICAL DEVELOPMENT OFFSHORE LATER THIS WEEK.
LOCALLY STRONG CONVECTION AND HEAVY RAINS MAY ALSO BE POSSIBLE IN
THE NORTH-CENTRAL U.S. AS SHORTWAVES ROUND TO THE EASTERN EDGE OF
THE UPPER RIDGE FROM THE ROCKIES/PLAINS AND INTERACT WITH A
DOWNSTREAM FRONTAL ZONE. LATE WEEK, EXPECT THE NORTHERN TO CENTRAL
PLAINS/UPPER MIDWEST/GREAT LAKES TO SEE PERIODIC RAIN AND
THUNDERSTORMS. WPC'S DAY 4/5 EROS DEPICT MARGINAL RISK AREAS FOR
THESE REGIONS THIS WEEKEND GIVEN MOISTURE/INSTABILITY POOLING WITH
SHORTWAVE PASSAGES. ACTIVITY WILL SPREAD INTO THE GREAT LAKES AND
THE CENTRAL PLAINS/MIDWEST THIS WEEKEND INTO NEXT WEEK. MEANWHILE,
THE SOUTHWEST/SOUTHERN ROCKIES STATES COULD SEE SOME INCREASING
MONSOON SHOWERS BY THIS WEEKEND, WITH MARGINAL RISK AREAS
INTRODUCED FOR PORTIONS OF ARIZONA AND NEW MEXICO FOR DAY 4/5.
COOLER THAN AVERAGE TEMPERATURES WILL CONTINUE ON THE COOL SIDE OF
THE MAIN FRONTAL SYSTEM FOR THE EAST/SOUTHEAST U.S., WHILE HEAT
LINGERS ACROSS THE SOUTHWEST AND SOUTHERN/CENTRAL PLAINS.
HEAT WILL ALSO SPREAD ACROSS PORTIONS OF THE MIDWEST AND GREAT
LAKES LATE THIS WEEKEND THEN EVENTUALLY THE NORTHEAST, WHICH MAY
CREATE A MAJOR HEATRISK. FLORIDA IS FORECAST TO SEE SEASONABLE
TEMPERATURES IN THE 90S, BUT WITH AMPLE HUMIDITY ALLOWING FOR SOME
AREAS OF MAJOR HEATRISK THERE AS WELL.
SCHICHTEL
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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