038
FXUS02 KWBC 300703
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 AM EDT SUN AUG 30 2026
VALID 12Z WED SEP 02 2026 - 12Z SUN SEP 06 2026
...DANGEROUS HEAT CONTINUES FROM THE CENTRAL AND SOUTHERN PLAINS
EASTWARD TO THE MIDWEST, MID-ATLANTIC, AND SOUTHEAST THROUGH LATE
WEEK...
..PATTERN OVERVIEW
A LATE SUMMER HEAT WAVE WILL CONTINUE TO BRING SCORCHING HOT
TEMPERATURES TO MUCH OF THE SOUTH-CENTRAL AND SOUTHEASTERN U.S.
THROUGH MID TO LATE WEEK BEFORE A COLD FRONT BRINGS SOME RELIEF
NEXT WEEKEND. MEANWHILE, A STRONG PACIFIC STORM COUPLED WITH A
POTENTIAL ATMOSPHERIC RIVER WILL BRING NOTABLE RAINFALL TO PARTS OF
THE PACIFIC NORTHWEST WEDNESDAY INTO THURSDAY. DOWNSTREAM, HEAVY
RAINFALL AND SEVERE WEATHER WILL BE POSSIBLE FROM THE NORTHERN
PLAINS AND THE UPPER MIDWEST TO THE GREAT LAKES, MID-ATLANTIC, AND
NORTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
A FAIRLY STABLE MID/UPPER LEVEL HEIGHT PATTERN REMAINS ENTRENCHED
ACROSS THE CONUS THROUGH THE MEDIUM RANGE PERIOD, FEATURING
PERSISTENT AND DEEP TROUGHING ACROSS THE WEST COAST, STOUT RIDGING
OVER THE CENTRAL AND SOUTHEASTERN U.S., AND INCREASING TROUGHING
ACROSS THE NORTHEASTERN U.S. OVERALL, THE LATEST AVAILABLE MODELS
HAVE A DECENT HANDLE ON THE LARGE SCALE PATTERN, BUT SPATIAL AND
TEMPORAL DIFFERENCES OF INDIVIDUAL WAVES (SEVERAL IMPULSES EJECTING
EASTWARD OUT OF THE WESTERN U.S. AND OVER TOP THE CENTRAL U.S.
RIDGE) BECOME MORE NOTABLE BEYOND DAYS 5 AND 6. AS A RESULT, THE
WPC FORECAST UTILIZED A BLEND OF DETERMINISTIC DYNAMICAL AND
MACHINE LEARNING GUIDANCE WITH A LEAN TOWARDS THE ECMWF SUITE
THROUGH DAY 5, THEN INCORPORATED MORE WEIGHTING TOWARDS THE
ENSEMBLE MEANS OF THE EPS AND GEFS (UP TO 50% OF THE BLEND) FOR
DAYS 6 AND 7. THIS APPROACH PRESERVED THE DOMINANT LARGE SCALE
PATTERN WHILE MITIGATING THE SPREAD OF SMALLER SCALE FEATURES.
..WEATHER/HAZARDS HIGHLIGHTS
INTENSE LATE-SUMMER HEAT WITH HIGH TEMPERATURES WELL INTO THE 90S
AND 100S WILL PERSIST FROM THE CENTRAL AND SOUTHERN PLAINS TO THE
MIDWEST, MID-ATLANTIC, AND SOUTHEAST THROUGH MID TO LATE WEEK AS A
LARGE AND SPRAWLING MID/UPPER RIDGE DOMINATES THE REGION. SOME
RELIEF IS POSSIBLE BY NEXT WEEKEND AS A COLD FRONT PRESSES IN FROM
THE NORTH (ESPECIALLY PARTS OF THE OHIO VALLEY AND MID-ATLANTIC),
BUT THE CORE OF THE HEAT WILL LIKELY CONTINUE FROM THE
CENTRAL/SOUTHERN PLAINS TO THE MID/LOWER MISSISSIPPI VALLEY INTO
THE SECOND WEEK OF SEPTEMBER. WELL ABOVE NORMAL TEMPERATURES
COMBINED WITH HIGH HUMIDITY AND VERY WARM OVERNIGHT LOWS IN THE 70S
TO NEAR 80 WILL RESULT IN WIDESPREAD AREAS OF MAJOR TO EXTREME
HEATRISK AND A CONCERN FOR HEAT-RELATED ILLNESSES. PLEASE SEE WPC'S
KEY MESSAGES FOR MORE DETAILS.
A PACIFIC STORM DESCENDING OUT OF THE GULF OF ALASKA COUPLED WITH
A WEAK TO MODERATE ATMOSPHERIC RIVER WILL BRING HEAVY RAINFALL TO
PARTS OF THE PACIFIC NORTHWEST WEDNESDAY THROUGH THURSDAY WITH
LIGHTER SHOWERS LIKELY LINGERING INTO FRIDAY. THE HEAVIEST RAIN
WILL MOSTLY FALL ON WEDNESDAY AND BE CONFINED TO COASTAL AREAS OF
WASHINGTON AND OREGON, ALONG WITH THE CASCADES. THE RAINY, CLOUDY,
AND GENERALLY UNSETTLED WEATHER ASSOCIATED WITH THE STORM ITSELF
AND PERSISTENT TROUGHING ALONG THE WEST COAST WILL HELP TO KEEP
TEMPERATURES ON THE COOLER SIDE OF NORMAL THROUGH THE END OF THE
WEEK AND INTO NEXT WEEKEND.
FARTHER DOWNSTREAM, A FRONTAL SYSTEM AND A SERIES OF MID-LEVEL
IMPULSES TRACKING EASTWARD ALONG THE NORTHERN PERIPHERY OF THE
ELONGATED MID/UPPER RIDGE WILL INTERACT WITH ANOMALOUS MOISTURE AND
INSTABILITY TO PRODUCE EPISODES OF HEAVY RAINFALL AND POSSIBLE
SEVERE WEATHER FROM THE NORTHERN PLAINS, UPPER MIDWEST, GREAT
LAKES, AND NORTHEAST MID TO LATE WEEK. ON WEDNESDAY IN PARTICULAR,
THERE IS A GROWING SIGNAL FOR SEVERE THUNDERSTORMS AND NOTABLE
RAINFALL ACROSS PORTIONS OF THE INTERIOR NORTHEAST AND NEW ENGLAND.
THE RAIN COULD BE HEAVY ENOUGH TO PRODUCE ISOLATED TO SCATTERED
INSTANCES OF FLASH FLOODING, ESPECIALLY IN URBAN, LOW-LYING, AND
POOR DRAINAGE AREAS.
ELSEWHERE, AFTER A BRIEF REPRIEVE, ANOTHER SURGE OF MONSOONAL
MOISTURE IS LIKELY TO BRING A RETURN TO MORE NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS PARTS OF THE SOUTHWEST AND INTERMOUNTAIN WEST
BY THURSDAY OR FRIDAY AND POSSIBLY LASTING THROUGH NEXT WEEKEND.
MEANWHILE, UNDERNEATH THE STRONG RIDGE TO THE NORTH, SMALL SCALE
DISTURBANCES INTERACTING WITH PLENTY OF MOISTURE WILL RESULT IN
DAILY CHANCES FOR SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE
DEEP SOUTH, GULF COAST, AND FLORIDA THROUGH NEXT WEEKEND. MANY OF
THESE STORMS WILL CONTAIN HEAVY RAINFALL RATES, LEADING TO THE
POTENTIAL FOR LOCALIZED FLASH FLOODING.
MILLER
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
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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