378 FXUS01 KWBC 050808 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sat Sep 05 2026 Valid 12Z Sat Sep 05 2026 - 12Z Mon Sep 07 2026 ...Rounds of strong to severe thunderstorms and locally heavy rain will slowly shift southward across the Midwest, Mid-Atlantic and into the Southeast during the Labor Day weekend... ...A front moving through the western U.S. could trigger heavy rain across Utah on Sunday... ...Heat persists across the midsection of the country while cooler air expands further into the West Coast and the Northeast... A deepening upper-level low in the vicinity of the Canadian Maritimes is bringing a cool air mass deeper into the northeastern U.S. As the leading edge of the cool air mass pushes against the heat dome across the midsection of the country, a corridor of strong to severe thunderstorms with scattered heavy rainfall will be triggered from the Midwest to the Ohio Valley, central/southern Appalachians, and into the Mid-Atlantic through the first half of Labor Day weekend. The most active thunderstorms are expected to be moving through the Midwest to the Ohio Valley this morning, followed by the central/southern Appalachians and into the Mid-Atlantic later today and into the evening. A slight risk of flash flooding is forecast closer to the Mid-Atlantic coast later today. By Sunday, the front will settle farther southward into the eastern U.S. This will confine the best chance for the stronger thunderstorms and heavy rain across the Southeast U.S. Behind the front, the cool air mass will break the recent spell of heat in the Northeast and Mid-Atlantic, where high temperatures in the mid-70s and low 80s can be expected by Sunday. Morning lows dropping into the 40s and 50s will bring a first taste of fall across New England for the latter half of the Labor Day weekend. Meanwhile, a deep upper-level low continues to move further inland across the northwestern U.S. where scattered showers and embedded thunderstorms can be expected through the Labor Day weekend. Farther south, monsoonal moisture will be lifted ahead of a slow-moving front. It appears that the best chance of showers and thunderstorms will be later on Sunday across the Great Basin, with locally heavy rain possible from southern Nevada through Utah, where WPC highlights a Slight Risk (level 2/4) of excessive rainfall. Urban areas, as well as dry washes and burn scars will be most vulnerable to flooding. Temperatures beneath the upper-low will be cool across the West this weekend as daytime highs dip 10 to 20 degrees below normal. In fact, below freezing morning temperatures are expected across the higher elevations as far south as northern California. Across the northern Plains, a low pressure system is consolidating ahead of the upper trough moving into the Pacific Northwest. Rounds of strong thunderstorms are expected to develop across the northern Plains around the north side of the system. The coverage and intensity of these thunderstorms and associated heavy rain are forecast to increase during the latter half of the Labor Day weekend especially across the northern High Plains as the low pressure system intensifies. In contrast, oppressive heat will continue through Labor Day in the Nation's Heartland as an upper-level ridge remains anchored over the midsection of the country. Heat indices of 105 to 110 degrees and record warm overnight temperatures will be widespread across the Central/Southern Plains States and Mississippi Valley this weekend. See WPC's Key Messages for more information on the heat, limit afternoon outdoor activity if possible, and stay hydrated regardless of your Labor Day plans. Kong/Asherman Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php Extreme Heat Key Messages available at: https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png $$