684
FXUS02 KWBC 280610
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 AM EDT FRI AUG 28 2026
VALID 12Z MON AUG 31 2026 - 12Z FRI SEP 04 2026
...DANGEROUS HEAT TO BROADLY EXPAND FROM THE CENTRAL AND SOUTHERN
PLAINS TO THE MIDWEST, SOUTHEAST, AND DEEP SOUTH NEXT WEEK...
..PATTERN OVERVIEW
AN INTENSIFYING LATE SUMMER HEAT WAVE WILL BRING EXTREME
TEMPERATURES TO THE CENTRAL/SOUTHERN PLAINS BEFORE EXPANDING TO THE
MIDWEST AND SOUTH NEXT WEEK. MEANWHILE, SURGES OF MONSOONAL
MOISTURE WILL CONTINUE TO SUPPORT DAILY SHOWERS AND THUNDERSTORMS
ACROSS PORTIONS OF THE SOUTHWEST AND THE INTERMOUNTAIN WEST/ROCKIES
WITH LOCALIZED FLASH FLOODING POSSIBLE. FARTHER NORTH, A
PROGRESSIVE SERIES OF STORM SYSTEMS WILL BRING ACTIVE WEATHER TO
THE PACIFIC NORTHWEST, ALONG WITH THE POTENTIAL FOR SEVERE WEATHER
AND HEAVY RAIN THREATS FARTHER DOWNSTREAM FROM THE NORTHERN PLAINS
AND UPPER MIDWEST TO THE NORTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST AVAILABLE MODEL GUIDANCE CONTINUES TO HAVE A RELATIVELY
GOOD HANDLE ON THE OVERALL LARGE SCALE PATTERN THROUGH THE MEDIUM
RANGE PERIOD, FEATURING SEVERAL BOUTS OF TROUGHING ACROSS THE
PACIFIC NORTHWEST, A POTENT SHORTWAVE/CLOSED LOW TRACKING EASTWARD
ALONG THE U.S./CANADA BORDER, AND AN ELONGATED UPPER RIDGE CENTERED
OVER THE CENTRAL AND SOUTHEAST U.S. (WITH AN UPPER LOW TRAPPED
UNDERNEATH ALONG THE GULF COAST). TIMING AND POSITIONAL DIFFERENCES
START TO INCREASE BEYOND DAY 5, SO THE WPC FORECAST UTILIZED A
COMPOSITE BLEND OF DETERMINISTIC AND MACHINE LEARNING GUIDANCE
(WITH A PREFERENCE TOWARD THE EC/EC-AIFS) BEFORE THEN. AFTER DAY 5,
THE BLEND GRADUALLY SHIFTED MORE WEIGHTING (UP TO 50%) TOWARDS THE
EC/GEFS ENSEMBLE MEANS TO MITIGATE THE SPREAD FOR DAYS 6 AND 7.
..WEATHER/HAZARDS HIGHLIGHTS
A SPRAWLING UPPER RIDGE EXPANDING FROM THE CENTRAL U.S. TO THE
SOUTHEAST U.S. WILL FOCUS AN INTENSIFYING AND LONG-LASTING LATE
SUMMER HEAT WAVE FROM THE CENTRAL/SOUTHERN PLAINS TO THE MIDWEST,
SOUTHEAST, AND DEEP SOUTH NEXT WEEK. HIGH TEMPERATURES CLIMBING
WELL INTO THE 90S AND 100S 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, INCREASING THE THREAT OF HEAT
RELATED ILLNESSES. PLEASE SEE WPC'S KEY MESSAGES FOR MORE DETAILS.
SURGES OF MONSOONAL MOISTURE AHEAD OF PERSISTENT PACIFIC NORTHWEST
UPPER TROUGHING AND CENTRAL/EASTERN U.S. UPPER RIDGING WILL
CONTINUE TO FUEL DAILY SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHWEST, INTERMOUNTAIN WEST,
AND ROCKIES THROUGH MOST OF NEXT WEEK. SOME THUNDERSTORMS ARE
LIKELY TO PRODUCE HEAVY RAINFALL WHICH MAY LEAD TO ISOLATED
INSTANCES OF FLASH FLOODING FOR MORE VULNERABLE AREAS LIKE BURN
SCARS, SLOT CANYONS, AND URBAN AREAS.
A SERIES OF DISTURBANCES TRACKING INTO THE PACIFIC NORTHWEST AND
ALONG THE U.S./CANADA BORDER WILL HIGHLIGHT A PERIOD OF ACTIVE
WEATHER ACROSS THE NORTHERN HALF OF THE COUNTRY OVER THE COURSE OF
NEXT WEEK. A POTENT SHORTWAVE/CLOSED UPPER LOW MOVING FROM SOUTH-
CENTRAL CANADA EASTWARD TO NORTHERN NEW ENGLAND AND VICINITY WILL
LEAD TO THE DEVELOPMENT OF A STRENGTHENING SURFACE LOW AND FRONTAL
SYSTEM WITH THE POTENTIAL TO BRING HEAVY RAINFALL AND SEVERE
WEATHER ACROSS PARTS OF THE NORTHERN PLAINS, UPPER MIDWEST, LOWER
GREAT LAKES, OHIO VALLEY AND THE NORTHEAST. MEANWHILE, PERSISTENT
TROUGHING AND REINFORCING SHORTWAVES CRASHING INTO THE PACIFIC
NORTHWEST COUPLED WITH A POSSIBLE ATMOSPHERIC RIVER MAY RESULT IN A
PERIOD OF HEAVIER RAINFALL FOR COASTAL AND MOUNTAIN REGIONS OF
WASHINGTON AND OREGON MID TO LATE NEXT WEEK. ADDITIONALLY, SOME
SNOW CAN'T BE RULED OUT ACROSS THE HIGHEST ELEVATIONS OF THE
CASCADES AS A POCKET OF COLDER AIR ALOFT MOVES OVERHEAD.
ELSEWHERE, DISSIPATING FRONTAL BOUNDARIES AND A SLOW-MOVING UPPER
LOW WILL LIKELY CONTRIBUTE TO A LINGERING THREAT FOR LOCALLY HEAVY
RAINFALL AND ISOLATED FLASH FLOODING CONCERNS OVER PORTIONS OF THE
GULF COAST, SOUTHEAST, AND FLORIDA NEXT WEEK.
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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