083
FXUS02 KWBC 041847
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 PM EDT MON AUG 4 2025
VALID 12Z THU AUG 07 2025 - 12Z MON AUG 11 2025
...MAJOR TO EXTREME HEAT THREAT FOR THE SOUTHWEST AND SOUTH-
CENTRAL PLAINS; THREAT SPREADS TO THE MIDWEST/GREAT LAKES LATE
WEEK...
..SOUTHEAST U.S. COASTAL LOW BEING MONITORED BY THE NHC
..OVERVIEW
A DEEP UPPER TROUGH WILL GRADUALLY TRANSIT EAST ACROSS THE
NORTHERN U.S., DRIVING THUNDERSTORM CHANCES FROM THE NORTHERN
ROCKIES TO THE MIDWEST. A WAVY FRONTAL BOUNDARY WILL LINGER ALONG
THE GULF AND SOUTHEAST COASTS, RESULTING IN UNSETTLED WEATHER FOR
PORTIONS OF THE SOUTHEAST AND MID-ATLANTIC, AND NHC IS MONITORING
A COASTAL LOW FOR POTENTIAL TROPICAL DEVELOPMENT MID/LATE WEEK.
MEANWHILE, A STRONG RIDGE WILL BE IN PLACE OVER THE SOUTHWEST AND
SOUTHERN/CENTRAL PLAINS, WHICH WILL CREATE A SIGNIFICANT MAJOR TO
EXTREME HEAT THREAT THROUGH THE END OF THIS WEEK. HIGH PRESSURE
RIDGING SHOULD EXTEND INTO THE MIDWEST/GREAT LAKES LATE THIS WEEK
INTO THE WEEKEND, RESULTING IN INCREASED TEMPERATURES AND
POTENTIALLY A MAJOR HEAT THREAT IN THESE REGIONS AS WELL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS SHOWING 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 ANCHORED OVER THE SOUTHWEST
AND A DEEP TROUGH SLOWLY MOVING EAST ACROSS THE NORTHERN U.S. WITH
SEVERAL EMBEDDED SHORTWAVES.
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 NORTHERN PLAINS/UPPER MIDWEST AND ALONG THE
SOUTHEAST COAST. IN THE SOUTHEAST, PRECIPITATION INTENSITY AND
LOCATION MAY BE AFFECTED BY ANY TROPICAL DEVELOPMENT THAT MAY OR
MAY NOT OCCUR LATER THIS WEEK. THE ECMWF AND ECENS ARE QUITE A BIT
HEAVIER WITH PRECIPITATION IN THE CAROLINAS WHILE OTHER MODEL
GUIDANCE AND THE NBM ARE LIGHTER IN THIS AREA WHILE FOCUSING THE
HEAVIEST PRECIPITATION RIGHT ALONG THE COAST. THE WPC FORECAST IS
CLOSER THE THE GENERAL CONSENSUS WITH SOME ENHANCEMENT ALONG THE
APPALACHIANS.
FOR WPC'S AFTERNOON FORECAST, THE MODEL BLEND CONSISTED OF EQUAL
AMOUNTS OF THE 06Z GFS AND 00Z CMC/ECMWF/UKMET. FOR DAYS 6 AND 7
(SUNDAY AND MONDAY), ENSEMBLE MEANS FROM THE GEFS/ECENS/CMCE WERE
ADDED TO SMOOTH OUT DIFFERENCES, BUT THE BLEND REMAINED 60%
DETERMINISTIC TO HELP MAINTAIN DETAILS OF INDIVIDUAL SYSTEMS.
..WEATHER/HAZARDS HIGHLIGHTS
A RATHER EXPANSIVE COOL HIGH PRESSURE AIRMASS WILL LINGER OVER THE
EASTERN U.S. THIS WEEK. HIGH MOISTURE CONTENT AND INSTABILITY NEAR
A FRONT ON THE LEADING EDGE OF THIS AIRMASS WILL FOCUS SOME
LOCALIZED HEAVY RAIN OVER THE SOUTHEAST, WHICH MAY RAISE FLASH
FLOODING RISKS GIVEN WET ANTECEDENT CONDITIONS. WPC'S EXCESSIVE
RAINFALL OUTLOOK (ERO) DEPICTS MARGINAL RISK AREAS FOR DAY
4/THURSDAY AND DAY 5/FRIDAY ALONG THE SOUTHEAST COAST AND INTO THE
SOUTHERN/CENTRAL APPALACHIANS AND MID-ATLANTIC. 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
LATER THIS WEEK.
LOCALLY HEAVY PRECIPITATION MAY ALSO BE POSSIBLE IN THE NORTH-
CENTRAL U.S. AS SHORTWAVES ROUND THE EASTERN EDGE OF THE UPPER
RIDGE FROM THE ROCKIES/PLAINS AND INTERACT WITH A DOWNSTREAM
FRONTAL ZONE. LATE WEEK, EXPECT THE NORTHERN PLAINS/UPPER
MIDWEST/GREAT LAKES TO SEE PERIODIC RAIN AND THUNDERSTORMS. WPC'S
DAY 4/5 EROS DEPICT MARGINAL RISK AREAS FOR THESE REGIONS ON
THURSDAY AND FRIDAY GIVEN LIKELY MOISTURE/INSTABILITY POOLING WITH
SHORTWAVE PASSAGES. PRECIPITATION SHOULD SPREAD INTO THE GREAT
LAKES AND MIDWEST THIS WEEKEND.
MEANWHILE, THE FOUR CORNERS STATES COULD SEE SOME INCREASING
MONSOON SHOWERS UNDERNEATH THE BROAD RIDGE, AMID THE RELATIVELY DRY
MONSOON SEASON SO FAR. ELSEWHERE, SOME MODERATE RAINFALL CHANCES
MAY DEVELOP AND SLOWLY PROGRESS THIS WEEKEND FROM OVER THE PACIFIC
NORTHWEST UNDER THE INFLUENCE OF A COOLING AND UNSETTLING UPPER-
LEVEL TROUGH.
COOLER THAN AVERAGE TEMPERATURES WILL CONTINUE ON THE COOL SIDE OF
THE MAIN FRONTAL SYSTEM FOR THE CENTRAL AND EASTERN U.S., WHILE
DANGEROUS HEAT BUILDS ACROSS THE SOUTHWEST AND SOUTHERN/CENTRAL
PLAINS. SOME LOCATIONS MAY SEE HIGH TEMPERATURES AS HIGH AS
110-115 DEGREES, EQUATING TO MAJOR TO EXTREME HEATRISK. SOME
RELATIVE RELIEF MAY COME NEXT WEEKEND AS THE UPPER HIGH BEGINS TO
WEAKEN. TEMPERATURES WILL ALSO BE WARMING TO ABOVE NORMAL ACROSS
PORTIONS OF THE MIDWEST AND GREAT LAKES LATE THIS WEEK INTO THE
WEEKEND AS THE UPPER RIDGE EXPANDS, WHICH MAY CREATE A MAJOR
HEATRISK. SOME RECORD HIGH TEMPERATURES COULD BE CHALLENGED AND/OR
ECLIPSED LATE THIS WEEK OVER THE SOUTHWEST. FLORIDA IS FORECAST TO
SEE SEASONABLE TEMPERATURES IN THE 90S, BUT WITH AMPLE HUMIDITY
ALLOWING FOR SOME AREAS OF MAJOR HEATRISK THERE AS WELL.
DOLAN/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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