446 FXUS02 KWBC 030716 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 316 AM EDT Mon Aug 3 2026 Valid 12Z Thu Aug 06 2026 - 12Z Mon Aug 10 2026 ...Heat wave continues through the week across the Southwest and Intermountain West, expanding northeastward with time... ...Overview... The upper ridge causing excessive heat atop the Southwest midweek will gradually intensify and expand north and east late week into next weekend, bringing hot temperatures across the Intermountain West to Plains and potentially into the South. Meanwhile, a handful of frontal systems in the central and eastern U.S. will trigger scattered showers and thunderstorms there, with monsoon convection in the Southwest as well. ...Guidance/Predictability Assessment... Models show good agreement on the large scale pattern evolution through the period, which features a northern stream trough through the north-central and then the Northeast U.S. and a sprawling southern tier ridge. The main focus of uncertainty continues to be with the positions of various energies aloft within the broader trough, as well as the timing of a shortwave into the Northwest which may finally act to erode the ridge over the Southwest. Models continue to trend towards more separation between the ridge over the Southwest and the subtropical Atlantic ridge with some weak energy in between them. This would allow for more tropical moisture intrusion and a wet pattern across the Southeast into at least early next week. Overall, there are not really considerable outliers with the pattern with differences well within the normal spread for the medium range. Thus the WPC forecast used a blend of deterministic guidance for the early part of the period, trending towards 50/50 ensemble means with deterministic guidance for Days 6 and 7. 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, as well as eastward in the Mid-South as the upper ridge expands. See Key Messages issued by WPC for this event for additional information regarding this long lasting and dangerous heat wave. Temperatures across the northern tier and into the East should be generally near average most of the period. A reasonably strong front will be moving through the Midwest and Central Plains by Thursday and trigger a corridor of potentially heavy rain and thunderstorms along and ahead of it. 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 to eastern U.S. through late week as the mean frontal boundary may stall for a bit. A wet pattern may set up by next weekend and early next week, especially for the Southeast, as tropical moisture rounds the west side of the 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. 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 $$