543 FXUS02 KWBC 031933 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 333 PM EDT Mon Aug 3 2026 Valid 12Z Thu Aug 06 2026 - 12Z Mon Aug 10 2026 ...Heat wave continues this week for the Southwest and Intermountain West, expanding northeastward with time... ...Overview... A strong upper-level ridge will persist over the southwestern U.S. and expand north and east over the weekend to allow excessive heat to expand across the Intermountain West into the High Plains. Monsoon convection will increase in the Southwest, which should help limit temperatures midweek. Meanwhile, upper troughing will dominate the pattern for the north- central and northeastern U.S. with several frontal boundaries moving east across these regions and triggering scattered showers and storms. Early next week, troughing will also develop over the Pacific Northwest, accompanied by cooling temperatures behind a weak cold front. ...Guidance/Predictability Assessment... Models show strong agreement on the synoptic scale pattern through early next week, with an expected amount of differences in the details. The main question with this forecast will be timing and location of shortwaves embedded in the broad trough over the north-central U.S. and Northeast. These waves will impact frontal evolution at the surface and impact precipitation chances. There are also some timing and evolution differences with energy moving into the Northwest late this weekend into early next week, though uncertainty is gradually decreasing. Overall models are handling precipitation chances well, but the separation between the southwestern ridge and subtropical Atlantic ridge could result in increasing precipitation chances for the Gulf Coast through the period. Given good agreement, the WPC forecast used a near even blend of deterministic guidance through the end of the week, with increasing contributions from ensemble means with deterministic guidance for the weekend and early next week. This maintained good continuity with the previous forecast. ...Weather/Hazards Highlights... For midweek, a slightly weaker upper ridge will allow for lessening HeatRisk across the Southwest compared to the short range period, though Moderate HeatRisk will still be widespread with isolated Major and Extreme values. Heat should build gradually northward across the Intermountain West and Rockies to the High Plains late this week into the weekend, and eastward towards the Mississippi Valley next week as the upper ridge expands. Temperatures across the northern tier and into the East should be generally near average most of the period, with a slight cooling trend expected for the Pacific Northwest in the wake of a weak/dry cold front this weekend. A reasonably strong front will be moving through the Midwest and Central Plains by Thursday with a corridor of potentially heavy rain and thunderstorms along and ahead of the frontal boundary. Meanwhile, weak frontal boundaries will allow for showers and thunderstorms to be scattered across the East, with some locally heavy to excessive rainfall possible there as well. These interacting features should allow for additional rounds of rain and storms across the north-central and eastern U.S. through late week as the mean frontal boundary may stall for a bit. A wet pattern may set up by the weekend and early next week, especially for the Southeast, as tropical moisture rounds the west side of the subtropical Atlantic ridge. Elsewhere, monsoonal convection is likely for Arizona and New Mexico in particular, with scattered convection occasionally reaching portions of Utah and Colorado. The remainder of the West into the Northern Plains should be mostly dry during the period. Dolan/Santorelli 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 $$