585 FXUS02 KWBC 250630 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 230 AM EDT Thu Jun 25 2026 Valid 12Z Sun Jun 28 2026 - 12Z Thu Jul 2 2026 ***Heat and humidity increases across the Central and Eastern U.S. for much of next week*** ...Pattern Overview... An anomalous upper low digging into the northwestern states will put an end to the heat wave across the Southwest and even lead to some higher elevation snow for the Montana and Idaho Rockies. This trough will spur surface cyclogenesis across the Plains with an occluded low lifting north across south-central Canada. In contrast, a building downstream upper ridge across the east-central U.S. will result in increasing heat and humidity going into much of next week with widespread 90s across the eastern half of the country. Showers and thunderstorms will be most likely across the Gulf Coast region, the southern Rockies, and the Upper Midwest. ...Guidance/Predictability Assessment... The 00Z model guidance suite is in relatively good agreement on most aspects of the forecast. The 12Z CMC was an outlier solution with respect to a stronger trough crossing the Upper Midwest and Great Lakes for early next week, whereas the other guidance and ensembles supported a stronger ridge axis. The 00Z CMC run is closer to the consensus, but still more suppressed with the upper ridge over the east-central U.S. compared to the other guidance. The GFS becomes stronger with a second trough building in across the Pacific Northwest late in the period. The WPC fronts/pressures were based on a general deterministic model blend for Sunday into Monday, with less of the CMC used given the differences noted across the Great Lakes region and greater run-to-run variations. This was followed by a higher percentage of the ensemble means towards Wednesday and Thursday. The NBM was a reasonable starting point for most areas of the country, although QPF was increased some for portions of western Texas and into central and eastern New Mexico with increasing monsoonal moisture on the back side of the upper ridge. In addition, temperatures were lowered for coastal areas of the Mid-Atlantic, Northeast, and the Great Lakes. ...Weather/Hazards Highlights... There should be an overall decrease in rainfall coverage going into Sunday across most of the country compared to the short range forecast period. There will likely be some showers and storms near the coastal Carolinas as a weak wave of low pressure develops offshore. Rain and mountain snow over central and western Montana should still be ongoing, with several inches of snow accumulation possible for the highest mountain ranges. Looking ahead to Monday/Tuesday, a corridor of showers and storms, some of which could be heavy, are forecast to develop from Nebraska to the Upper Peninsula of Michigan ahead of the cold front crossing the Upper Midwest. Elsewhere across the country, some thunderstorms are likely to develop in the vicinity of the dryline across western Texas and eastern New Mexico for the first half of the week, with a higher trend compared to previous forecasts. Scattered showers and thunderstorms are expected from the central Gulf Coast to the Florida Peninsula with moisture increasing south of the upper ridge, with most of these happening during the afternoon and evening hours. A temperature dichotomy will exist across the country starting this weekend as the deep upper trough heralds the arrival of much cooler conditions starting across the Pacific Northwest and northern Rockies, with highs running on the order of 15-25 degrees below late June averages. This will likely be cold enough to come close to some new daily record low temperatures. The opposite will hold true from the Plains to the Ohio Valley with widespread above average temperatures expected with the strong upper ridge developing. Highs in the 90s are expected as far north as the Great Lakes and Minnesota, and 100s for much of Texas. Some 100+ degree readings are also possible for portions of the Southeast by Thursday. Heat indices approaching 110 degrees are possible from the Mid-South to the central Gulf Coast where the combination of heat and high dewpoints will be greatest. Overnight lows will also be quite warm, with some record high minimums possible. 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 $$