234
FXUS02 KWBC 241815
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
215 PM EDT MON AUG 24 2026
VALID 12Z THU AUG 27 2026 - 12Z MON AUG 31 2026
...HAZARDOUS HEAT CONTINUES FROM THE DESERT SOUTHWEST TO THE
SOUTHERN PLAINS...
..OVERVIEW
THE UPPER LEVEL PATTERN WILL FEATURE TROUGHING IN THE NORTHWEST AND
EAST WITH A STRONG RIDGE ANCHORED OVER THE SOUTHWEST. THE RIDGE
WILL FLATTEN LATE THIS WEEK AS UPPER LEVEL TROUGHING STRENGTHENS
OVER THE NORTHWEST, BRINGING RELIEF FROM THE ONGOING HEAT WAVE TO
SOME AREAS, BUT HAZARDOUS HEAT WILL PERSIST FROM THE DESERT
SOUTHWEST TO THE SOUTHERN PLAINS. THE RIDGE OF HIGH PRESSURE WILL
BE SHUNTED EAST THIS WEEKEND, RESULTING IN EXPANDING HEAT ACROSS
THE SOUTH-CENTRAL UNITED STATES. MOISTURE ON THE WESTERN PERIPHERY
OF THE RIDGE WILL CONTINUE TO SUPPORT DAILY MONSOONAL CONVECTION
ACROSS THE INTERMOUNTAIN WEST. MEANWHILE, SEVERAL FRONTAL SYSTEMS
WILL PUSH THROUGH THE UPPER TROUGHS, BRINGING SHOWERS AND
THUNDERSTORMS FROM THE NORTHERN/CENTRAL PLAINS TO THE EAST AND
SOUTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE SYNOPTIC WEATHER
PATTERN, WITH AN EXPECTED AMOUNT OF UNCERTAINTY IN THE DETAILS OF
INDIVIDUAL SYSTEMS. UNCERTAINTY HAS DECREASED SIGNIFICANTLY OVER
THE PAST 24 HOURS WITH ENERGY MOVING INTO THE NORTHWEST THIS
WEEKEND. THE GFS WAS PREVIOUSLY AN OUTLIER ON THE SOUTHERN EDGE OF
GUIDANCE SPREAD, BUT GUIDANCE HAS TRENDED SOUTH IN AGREEMENT WITH
THE GFS OVER THE PAST FEW RUNS. THE UKMET HAS BEEN SLOWER TO SHIFT
SOUTH, BECOMING THE NORTHERN EDGE OF THE SPREAD.
WITH ENERGY DIGGING FURTHER SOUTH INTO THE NORTHWEST AND EJECTING
ACROSS THE NORTHERN TIER, PRECIPITATION CHANCES HAVE INCREASED
WITH THIS FORECAST. THERE IS SOME UNCERTAINTY IN THE SPEED OF THIS
FEATURE, TRENDING A LITTLE FASTER TODAY THAN THE OVERNIGHT
FORECAST.
GIVEN GOOD AGREEMENT, THE WPC FORECAST WAS INITIATED USING A NEAR
EVEN BLEND OF THE AVAILABLE DETERMINISTIC AND AI GUIDANCE,
EXCLUDING THE UKMET FOR REASONS STATED ABOVE. ENSEMBLE MEANS FROM
THE GEFS AND ECENS WERE ADDED IN INCREASING AMOUNTS THROUGH THE
WEEKEND INTO EARLY NEXT WEEK TO SMOOTH OUT MODEL DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
STILL UNDER THE INFLUENCE OF THE UPPER HIGH/RIDGE, DAILY MAXIMUM
TEMPERATURES ACROSS THE SOUTHERN PLAINS WILL CONTINUE TO RISE INTO
THE 90S AND 100S WITH OPPRESSIVE HEAT INDICES. RECORD-BREAKING
WARM OVERNIGHT TEMPERATURES ACROSS THE SOUTHERN TIER WILL FURTHER
LIMIT RECOVERY FROM THE HEAT, RESULTING IN WIDESPREAD MAJOR TO
EXTREME HEATRISK THAT MAY CAUSE HEAT RELATED ILLNESSES. AS THE
UPPER RIDGE FLATTENS, HEAT WILL BE LIMITED TO SOUTHERN TEXAS, BUT
HEAT WILL EXPAND NORTH ACROSS THE SOUTHERN PLAINS AND EAST TOWARDS
THE LOWER MISSISSIPPI VALLEY THIS WEEKEND AS THE RIDGE SHIFTS EAST.
FOR THE DESERT SOUTHWEST, DAILY MAX TEMPERATURES ARE FORECAST TO
SOAR INTO THE 110S, WHICH WILL CREATE HEAT CONCERNS THIS WEEK.
PLEASE SEE WPC'S KEY MESSAGES FOR MORE EXTREME HEAT DETAILS.
MONSOONAL MOISTURE STREAMING NORTHWARD ON THE WESTERN PERIPHERY OF
THE UPPER RIDGE WILL FUEL SCATTERED, DIURNALLY DRIVEN CONVECTION
FROM THE SOUTHWEST TO THE ROCKIES. INDIVIDUAL CELLS MAY LEAD TO
ISOLATED INSTANCES OF FLASH FLOODING FOR SENSITIVE LOCATIONS SUCH
AS BURN SCARS, FAVORED TERRAIN LIKE SLOT CANYONS, AND URBAN AREAS.
THERE IS A MARGINAL RISK FOR PORTIONS OF THE SOUTHWEST IN THE WPC
DAY 4/THURSDAY AND DAY 5/FRIDAY EXCESSIVE RAINFALL OUTLOOKS (EROS).
SHORTWAVES ROUNDING THE TOP OF THE RIDGE AND PIVOTING INTO THE
EASTERN MEAN UPPER TROUGH WILL PERIODICALLY TRIGGER SHOWERS AND
SOME STRONG THUNDERSTORMS FROM THE NORTHERN AND CENTRAL PLAINS TO
THE MIDWEST THIS WEEK. A MARGINAL RISK ERO COVERS THIS THREAT.
DOWNSTREAM, ELONGATED ERO MARGINAL RISK AREAS ARE HIGHLIGHTED FOR
PORTIONS OF THE SOUTHEAST AND MID-ATLANTIC THAT MAY SEE REPEATED
ROUNDS OF LOCALLY HEAVY PRECIPITATION AS WAVY FRONTAL BOUNDARIES
APPROACH AND ULTIMATELY STALL OVER THESE REGIONS. HEAVY RAINFALL
POTENTIAL MAY BE RENEWED ACROSS THE NORTHERN PLAINS AND MIDWEST
THIS WEEKEND INTO EARLY NEXT WEEK WITH A STRONGER FRONTAL SYSTEM
PUSHING ACROSS AN UNSETTLED NORTHWEST INTO THE NORTHERN PLAINS AND
UPPER MIDWEST.
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, 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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