784 FXUS02 KWBC 041833 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 233 PM EDT Tue Aug 4 2026 Valid 12Z Fri Aug 07 2026 - 12Z Tue Aug 11 2026 ...Heat wave continues through the weekend for the Southwest, with some expansion into the Intermountain West... ...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. Meanwhile, expect a progressive northern stream with a trough and surface front moving across the northern U.S. into the East with a continued wet pattern. A trend for heavier rainfall is looking more likely across portions of the Great Lakes and vicinity next week. Troughing will also move into the Northwest, and should finally weaken the Southwest ridge, ending the oppressive heat wave. ...Guidance/Predictability Assessment... The latest deterministic and mean guidance remains well clustered on an overall fairly predictable synoptic pattern this weekend and into early next week. A pair of upper-highs will be in place over the subtropical Atlantic and Southwest with a northern stream situated along the norther tier/Canadian border beneath and upper- low hovering around Hudson Bay. Most of the forecast uncertainty is tied to precipitation coverage/amounts both on the western side of the upper-high through the Southeast/Ohio Valley and along the East Coast as well as through the Midwest as embedded energies round the upper-low in the northern stream. The latest NBM QPF looked to be on the lighter side overall for the Southeast/Ohio Valley and along the East Coast, though with sporadic/uncertain periods of convection saw little reason to deviate from the 13Z NBM for now. Much of the deterministic guidance also shows the potential for an axis of heavier precipitation along a cold front pushing into the Interior Northeast/Ohio Valley west through the Great Lakes/Midwest early next week. The latest NBM showed similar potential and appeared to be a good compromise position wise for now with the heaviest rainfall focused on the Upper Midwest/Great Lakes Monday and then the Lower Great Lakes/Upper Ohio Valley into Tuesday. The updated WPC forecast package used a composite blend of the ECMWF/ECMWF AIFS/GFS/CMC/UKMET given the good overall agreement. A contribution from the ECens mean was included for the latter part of the period given the time-limited UKMET and also as the GFS contribution was brought down due to a bit more intense cyclogenesis in the lee of the Rockies early next week compared to the other guidance. The 13Z NBM was sufficient for most regions QPF-wise as noted with just a modest increase of QPF throughout the Southwest given active Monsoon activity. ...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. Areas of smoke will also remain likely given active fires. Heat across the Southwest should finally wane by early next week with increasing monsoonal moisture and a weakening upper ridge. 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. Interaction between a weakening front in the East and a strong one into the northern Plains and Great Lakes later this week will allow for ongoing showers and storms across the Midwest to the East. A wet pattern looks to set up by the weekend and into early next week, especially for the South and Southeast, as tropical moisture rounds the west side of the subtropical Atlantic ridge. More widespread, moderate to heavy rainfall is also looking increasingly likely across portions of the Upper Midwest/Great Lakes/Upper Ohio Valley early next week. Monsoonal moisture is likely to continue into next week for Arizona and New Mexico, reaching portions of Utah and Colorado as well. The remainder of the West into the Northern Plains should be mostly dry during the period. Putnam/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 $$