Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
740 FXUS02 KWBC 290755 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 355 AM EDT Wed Jul 29 2026 Valid 12Z Sat Aug 1 2026 - 12Z Wed Aug 5 2026 ***Hot weather continues for the Intermountain West and the Desert Southwest with daily record highs likely*** ...Pattern Overview... The large upper ridge that will be governing the overall weather pattern across the western half of the country will start to shrink some going into the week. This will be due to a strong closed upper low/trough moving into southwestern Canada, with a trailing cold front bringing a welcomed cool down from the Pacific Northwest to the Northern Plains after a very hot week. Meanwhile, an amplifying trough over the Midwest and then the Mid-South will lead to increased showers and thunderstorms from the Gulf Coast to the Northeast going into Sunday and the beginning of the work week, thus keeping any excessive heat away from the Eastern U.S. through Tuesday. It will still remain quite hot from the Desert Southwest into Texas since the cold front will not make it that far south. ...Guidance/Predictability Assessment... The 00Z model guidance suite features good overall synoptic scale agreement across the Continental U.S. going into next weekend, with the best agreement noted on the closed upper high positioned across the southwestern quadrant of the country. There has been good run-to-run continuity since the 12Z guidance in most cases through Monday, and the most recent GFS has trended closer to the model consensus with the trough across the Northeast early in the week compared to its 18Z run, which was a much stronger solution compared to the existing guidance. The ECMWF/AIFS/ECENS hold onto a broad upper low/trough over the Ohio Valley and the Mid-South longer than the CMC/GFS guidance through Tuesday. In terms of the NBM, it appeared reasonable as a starting point for most areas, although some modest downward adjustments were made for portions of the interior Northwest into the Dakotas behind the cold front to be closer to the model consensus. The ensemble means were gradually increased to about 40% by next Wednesday. ...Weather/Hazards Highlights... The Ohio Valley and Mid-South are expected to get an increase in rainfall coverage for Saturday as a shortwave trough drops down from the Great Lakes and possibly becomes a weak cut-off upper low. A more concentrated area of heavier rainfall will be possible from the central Gulf Coast to northern Florida with enhanced moisture convergence south of the frontal boundary, with some rainfall totals in excess of two inches over the weekend. Showers and thunderstorms increase more broadly across the East Coast states in general for Sunday into Monday as deeper moisture is advected northward ahead of the upper trough across the Mid-South, potentially more concentrated across the central and southern Appalachians. The western U.S. heat wave is expected to be worst on Saturday with highs at or above 100 degrees from California to the northwestern High Plains. The potential exists for numerous daily records to be set, and some possibly close to monthly records for August. There will likely be some record heat going into Sunday as well, but only extending up to central Wyoming since a cold front will be passing through Idaho and Montana. The hottest readings for the weekend will be across the lower elevations of the Desert Southwest where widespread 110s are forecast, and even some lower 120s for the normally hottest locations! Record high overnight lows are also likely, including locations farther to the east across Texas with lows struggling to get below 80 degrees. It will remain uncomfortably hot going into the first half of next week from California to Utah and southward to Arizona where the upper ridge persists the longest. Elsewhere across the Continental U.S., most of the monsoonal rainfall should be confined to eastern Arizona and into New Mexico, with scattered convection reaching into portions of Utah and Colorado. A corridor of showers and storms is likely ahead of the front that crosses the Dakotas and into Minnesota early in the week, and this may also be accompanied with some severe weather. The Pacific Northwest will likely have some below average temperatures this weekend before a gradual warm-up ensues next week, and generally close to average for the eastern U.S. Hamrick 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 $$