811 FXUS02 KWBC 181851 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 PM EDT Fri Jul 18 2025 Valid 12Z Mon Jul 21 2025 - 12Z Fri Jul 25 2025 ...Major heat wave building from the Southeast into parts of the Central U.S. next week and beyond... ...Overview... A good guidance signal remains that indicates that the overall weather pattern next week will be dominated by a building upper level ridge that will be situated over the Deep South and extending north to the Tennessee and Ohio River valleys. Heat and humidity build to dangerous levels across much of the Central U.S. and extending to the Southeast states. An active flow pattern will be in place to the north of this high as multiple shortwave impulses track eastward over the northern tier states and then reach New England. A cold front provides some relief from the recent heat and humidity from the Mid-Atlantic to the Northeast to by the start of next week. Meanwhile, an upper level trough likely develops near the West Coast going into early next week, with some potential for an upper low to develop. ...Guidance/Predictability Assessment... Latest guidance solutions are overall clustered better than normal valid for early-mid next week and a favored model composite has good ensemble support. Favor a switch to a seemingly reasonable composite of the compatible GEFS/ECMWF/Canadian ensemble means along with the best matching ECMWF model for some detail amid slowly increasing forecast spread and local uncertainty. ...Weather/Hazards Highlights... It still remains the case that a corridor of unsettled weather will remain in place from the Upper Midwest to the Southeast coast for the beginning of the week. Thunderstorm complexes traveling around the northern periphery of the big upper high will likely produce localized areas of heavy rainfall. Therefore, a broad Marginal Risk area extends from the eastern Dakotas and Upper Midwest through the Ohio Valley, and to northern Florida and the coastal Carolinas for both Days 4 and 5 (Monday and Tuesday). Local focus remains more run-run dependent, but latest trends show best potential has now shifted for early-mid next week to the Upper Midwest as impulses work over moisture/instability pooling fronts. There is then also a growing signal that impulse energy may refind a track around and underneath the main upper ridge from the Southeast/Florida back into the northern Gulf into later next week to monitor for development and/or local Gulf Coast QPF enhancement. Heat will once again make weather headlines for much of next week across a large portion of the southern and central U.S. with a large upper high becoming anchored over the Mid-South. Widespread major impacts on the Heat Risk scale are expected from the Central Plains to the Southeast states early in the week, and these higher impacts then reach the Midwest and Ohio Valley by mid to late week. This will be due to widespread highs in the middle 90s to low 100s for many of these areas, in combination with dewpoints well into the 70s, and overnight lows remaining uncomfortably warm. This will likely have some staying power beyond this forecast period based on the latest week two outlook from the Climate Prediction Center from the Central Plains to the Deep South. Elsewhere across the nation, there should be just enough monsoonal moisture in place across eastern Arizona and much of New Mexico, and probably extending into southern portions of Colorado, and given the potential for some isolated slow moving storms, a Marginal Risk is in place for both Monday and Tuesday. Across the East Coast region, a cold front is forecast to clear the Northeast and the Mid-Atlantic region, and bringing a higher quality airmass after all of the heat and oppressive humidity lately and lower rain chances. However, the heat will likely return towards the end of the week as the Canadian surface high moves offshore and a more southerly flow commences. Hamrick/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 $$