383 FXUS02 KWBC 260707 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 307 AM EDT Wed Aug 26 2026 Valid 12Z Sat Aug 29 2026 - 12Z Wed Sep 02 2026 ...Hazardous Heat from the Desert Southwest and Texas to reposition across the South-Central U.S. and Mid-South... ...Overview... Dangerous late summer heat continuing across the Desert Southwest and Texas will spread northward across the central/southern Plains and Mid-South this weekend into next week. Surges of monsoonal moisture will support daily showers and thunderstorms over portions of the Southwest and Intermountain West/Rockies with localized flash flooding possible. Meanwhile, several lows/frontal systems will push across the northern tier of the CONUS and dig into the east-central U.S. to bring multiple chances for strong to severe thunderstorms with locally heavy downpours. Lingering lead frontal boundaries across the southern Mid-Atlantic and Southeast will offer lingering risks for storms with heavy rain/runoff issues. ...Guidance/Predictability Assessment... Guidance remains in overall good agreement on the synoptic weather pattern, though uncertainty with the timing of systems working through the Northwest to the U.S. northern tier remains. Given continued larger scale agreement, favor a composite model to ensemble mean/machine learning guidance blend solution over time that seems to provide a good general forecast and threat messaging baseline in line with continuity. The blend process tends to mute/mitigate embedded smaller scale system differences as consistent with individual predictability, but maintains main focusing features. ...Weather/Hazards Highlights... Under the influence of the upper high/ridge this week, 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 into this weekend and shifts eastward into early-mid next week, hazardous heat will refocus over the southern Plains and steadily expand north across the south-central U.S and Mid-Lower Mississippi Valley/Mid-South with some triple digit maximum temperatures and more widespread record hot overnight values. In this upper pattern transition, expect excessive heat threat moderation over the Desert Southwest this weekend into next week. Please see WPC's Key Messages for more extreme heat details. Monsoonal moisture streaming northward on the western to northern periphery of the upper ridge and ahead of locally showery Northwest U.S. upper troughing will continue to fuel scattered, diurnally driven convection from the Southwest and Intermountain West 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. Marginal Risk areas cover portions of these broad areas on the WPC Day 4/Saturday and Day 5/Sunday Excessive Rainfall Outlooks (EROs). Shortwaves rounding the top of the ridge and pivoting into the downstream mean upper trough while interacting with wavy frontal systems will periodically trigger episodes of heavy rain and strong to severe thunderstorms from the Plains to the Midwest then Northeast this weekend into next week. Weekend Marginal Risk ERO areas spotlight a focus over the Upper Midwest. Meanwhile downstream, weekend Marginal Risk ERO areas highlight a protracted threat for repeated rounds of locally heavy rainfall for the southern Mid-Atlantic and the coastal Southeast/Florida as wavy frontal boundaries approach and stall over these moist regions. 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 $$