Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 233 PM EDT Sat Aug 31 2024 Valid 00Z Sun Sep 01 2024 - 00Z Tue Sep 03 2024 ...Unsettled weather across the East through Sunday... ...Multiple days of heavy rain may cause flash flooding for portions of central Texas and the western Gulf Coast... ...Well above average, hot late-summer temperatures forecast in the northwestern U.S. this holiday weekend... An upper-level trough and associated surface cold front will progress eastward this weekend, extending from the Northeast southwest through the Ohio/Tennessee Valleys, Middle Mississippi Valley/Mid-South, and into the Southern Plains. A round of showers and thunderstorms is expected along and ahead of the length of the front through tonight, with moist air and instability likely leading to some more intense thunderstorms, heavy downpours, and the potential for isolated flash flooding. A locally higher threat is expected across portions of the northern/central Appalachians given the potential for some training/repeated rounds of storms across more sensitive mountain terrain. The region is under a Slight Risk of Excessive Rainfall (level 2/4) for the threat of a few more scattered instances of flash flooding. In addition, stronger winds aloft with the passing upper trough will bring increased shear for some more organized storms. The Storm Prediction Center has also included a Slight Risk of severe weather (level 2/5), mainly for the threat of some damaging winds. The fronts forward progression will slow through into early Sunday, especially with southwestward extent, leading to additional rounds of storms on Sunday with moderate to locally heavy rainfall from the southern Mid-Atlantic/Carolinas west through the Tennessee Valley, Mid-South, and into the Southern Plains. Some isolated flash flooding will remain possible, especially for the southern Appalachians/Mid-Atlantic and Carolinas. A secondary cold front sweeping in from the north will bring an end to precipitation chances for most areas outside of the Southeast/Southern Plains later Sunday night. Further south, another area of storms is expected to continue today in vicinity of a coastal low near the western Louisiana and upper Texas Gulf Coasts. Another Slight Risk of Excessive Rainfall is in place as slow moving and very heavy rainfall-producing storms given abundant Gulf moisture may lead to some additional scattered instances of flash flooding, especially given wetter antecedent conditions from rainfall the past few days. At least an isolated threat for flash flooding will exist into Sunday, though rainfall amounts may trend downward. Shower and thunderstorm chances should increase to end the weekend and into Labor Day throughout central Texas as a lingering stalled frontal boundary and upper-level energy ejecting out of northern Mexico combine to produce areas of heavy rain and scattered flash floods. Daily thunderstorms are also forecast for the Florida Peninsula, with some isolated instances of urban flooding possible for South Florida today. Temperature-wise, relief from the more intense heat this past week will finally come to the Middle Mississippi, Ohio, and Tennessee Valleys as increasing storm chances and the approaching front keep temperatures down a bit, with highs generally in the 80s and low 90s. Low 90s will also be common across the Southeast with mid-80s to low 90s for the Appalachians and southern Mid-Atlantic. Highs will remain cooler and mainly in the 70s to the north of a warm front for the northern Mid-Atlantic and New England Saturday, with a rebound into the low 80s expected for many locations Sunday as the warm front lifts north. The Northern/Central Plains and Midwest will see highs in the 80s today before a cold front brings cooler temperatures in the 70s Sunday. Conditions will remain much below average for late Summer over the Lower Mississippi Valley and Southern Plains, with highs generally in the mid-80s outside of south Texas. Some 70s will be possible for west Texas. Well above average, hot late-summer temperatures will continue into the weekend for the northwestern U.S. as a broad upper-level ridge remains in place over the West. Highs are forecast into the 90s to near 100 across the interior Pacific Northwest, northern Great Basin, and northern Rockies, which have prompted some Heat Advisories for the northern Great Basin/Rockies given the heightened risk of heat-related illness. This heat is then forecast to shift eastward into the northern High Plains and northern Rockies on Labor Day, with highs also reaching into the mid-to-upper 90s. Those with outdoor plans for the holiday weekend should remember to take more frequent breaks from the heat in the shade and stay hydrated. Highs elsewhere across the West will not be quite as above average, but still hot, with 90s for the Great Basin and interior California and 100s in the Desert Southwest. Portions of the Southwest/Four Corners Region will be a bit cooler with shower and thunderstorm chances expected in vicinity of a lingering frontal boundary, with highs in the upper 70s and 80s. Snell/Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php