FXUS02 KWBC 231919 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 319 PM EDT Sun Aug 23 2026 Valid 12Z Wed Aug 26 2026 - 12Z Sun Aug 30 2026 ...Hazardous Heat to continue for the Desert Southwest and 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, resulting in some areas seeing relief from the ongoing heat wave, but hazardous heat will persist for the Desert Southwest and southern Plains. 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 storms from the northern/central Plains to the East Coast. ...Guidance/Predictability Assessment... Model guidance remains in good agreement on the synoptic pattern through the week, with some uncertainty creeping in next weekend as upper level energy moves into the Northwest and across the northern tier. The GFS is on the southern/western side of the guidance spread while the ECMWF is on the northern/eastern side. The placement of this energy will affect precipitation chances from the Pacific Northwest to the northern Plains, a northern solution would result in little to no precipitation while a southern solution could bring significant precipitation. AI guidance suggests a middle of the road solution, which was favored for today's forecast. Given good agreement, the WPC forecast was initiated with a near even blend of the deterministic guidance, and contributions from the GEFS, ECENS, AI GFS, and EC-AIFS were added late week into the weekend to help smooth out model differences. This blend was consistent with the previous forecast and the National Blend of Models. ...Weather/Hazards Highlights... Under the influence of the main 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, especially given heatwave longevity which may result in heat related illnesses. Conditions will improve this week for the Lower Mississippi Valley, but widespread Major to Extreme HeatRisk will persist in the southern Plains. For the Desert Southwest, daytime max temperatures are forecast to soar into the 110s, which will create heat concerns this week. Pre- frontal areas of the Southeast may be a few degrees above normal, but forecast precipitation and cloud cover will help keep the heat in check. Please see WPC's Key Messages for more extreme heat details. Meanwhile, lingering monsoonal moisture will stream northward on the periphery of the upper ridge to help trigger scattered, diurnally driven convection across the eastern Intermountain West and 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 of excessive rainfall for these areas in the Day 4 (Wednesday) and Day 5 (Thursday) outlooks. Marginal Risk areas are also highlighted for portions of the Southeast and Mid-Atlantic that may see repeated rounds of locally heavy precipitation as frontal boundaries approach and ultimately stall over these regions. Shortwaves rounding the top of the ridge will trigger showers and thunderstorms from the northern and central Plains into portions of the Midwest through mid-week. Later this week, a stronger frontal system will push across the Northwest and north-Central U.S., bringing increasing precipitation chances and potentially heavy rainfall to the Plains and Midwest. Warm, southerly flow on the southern side of the system may bring increasing heat to the southern and central Plains next weekend. 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 $$