657 FXUS02 KWBC 270754 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 354 AM EDT Mon Jul 27 2026 Valid 12Z Thu Jul 30 2026 - 12Z Mon Aug 3 2026 ***Long duration heat wave expected for much of the Western U.S. and western High Plains*** ...Pattern Overview... The main theme going into the middle of the week will be a large upper ridge situated across the Rockies and western High Plains that will result in a lengthy heat wave. An upper trough with a closed low is expected over the Northeast Pacific, and an amplified trough will be departing the Northeast states with the heaviest rainfall exiting the coast. General troughing likely continues for the East Coast as a second trough amplifies over the Midwest and brings additional prospects for showers and storms. ...Guidance/Predictability Assessment... The 00Z model guidance suite features good overall synoptic scale agreement across the Continental U.S. to close out the work week, with the best agreement noted on the closed upper high positioned across the interior Western U.S. through the weekend. The guidance has started coming into better focus with a shortwave trough tracking from the Upper Midwest to the Tennessee Valley through early Sunday, with the GFS slightly more progressive in bringing the trough southward. The UKMET differed the most with a stronger surface low over Illinois by Saturday morning, whereas the model consensus is farther south and weaker. There is also improved agreement with the northeast Pacific closed low/trough that moves inland across southern Canada by Sunday into Monday, although the GFS/GEFS is a little less amplified than the ECMWF/CMC across Montana and Idaho. The ensemble means were gradually increased to about 40% by next Monday. ...Weather/Hazards Highlights... The coastal low that will be affecting the Northeast U.S. for the middle of this week will slowly exit the region and take most of the heavy rainfall out to sea by Thursday afternoon. Lingering showers and breezy conditions will remain across New England through Thursday night. The area with the heaviest rainfall to close out the work week will likely be across the Midwest as a shortwave disturbance aloft promotes the development of mesoscale convective complexes that will likely bring multiple rounds of heavy rainfall and strong thunderstorms, with a Slight Risk of excessive rainfall extending from eastern South Dakota to Illinois over the Thursday to Friday time period. Additional heavy rainfall is likely across portions of the Deep South and Gulf Coast region going into next weekend as a frontal boundary stalls out across the region, and showers/storms become more widespread for the Eastern U.S. by Sunday and into Monday. Daily afternoon and evening thunderstorms are expected from the central Rockies to the Desert Southwest through Saturday, with slightly less monsoonal moisture expected into Sunday and Monday as the upper high expands over the region. Widespread heat will continue to make weather headlines across a large portion of the western and central U.S. as a large upper ridge becomes parked over the southwestern quadrant of the country. The most extreme heat is expected over the lower elevations of the Desert Southwest through much of the forecast period, with highs well into the 110s and approaching 120 degrees in some instances, and readings near 100 degrees extending north into southern Idaho and westward to include the Central Valley of California. Another area of excessive heat is likely from Montana into western portions of the Dakotas with highs reaching or surpassing 100 degrees next weekend before a cold front passes through early next week. Hot and humid conditions will continue through the end of the week across the Gulf Coast region, with heat indices on the order of 105-115 degrees with dewpoints well into the 70s south of the stalled front. A slight abatement in the heat is likely by the weekend with more clouds and rainfall across the region. 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 $$