Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 319 PM EDT Sat Jul 31 2021 Valid 00Z Sun Aug 01 2021 - 00Z Tue Aug 03 2021 ...Excessive heat continues today over the interior Pacific Northwest, the South-Central U.S., and the Deep South before a cooling trend begins in on Sunday... ...Strong to severe thunderstorms with locally heavy rainfall from the Central Plains and mid-Mississippi Valley to the Southeast this afternoon reaches the Gulf Coast for Sunday and Monday... ...More rounds of monsoonal moisture expected across the interior western U.S. with flash flooding possible from the Great Basin to the Rockies... Oppressive summer heat has taken a vacation this weekend throughout the Midwest, Great Lakes, and Northeast thanks to a cold front ushering in a much cooler and drier airmass. Saturday's stifling heat across the Deep South and Southeast will improve slightly on Sunday but a hot and humid air-mass remains in place to close out the weekend. However, a cold front responsible for the injection of cooler and drier conditions in the Northeast this weekend eventually reaches the Deep South by Monday. Muggy conditions will likely persist along the Gulf Coast while comfortable humidity levels stick around in the Northeast and Great Lakes into start of the work-week. Precipitation-wise, waves of low pressure developing along an elongated frontal boundary draped from the central High Plains to the Southeast is forecast to trigger organized thunderstorms that could produce isolated tornadoes, damaging wind gusts, and large hail today from Kansas to the Carolinas. In addition, heavy downpours associated with these thunderstorms could lead to flash flooding in the mid-Mississippi River Valley today. The threat for severe weather and flash flooding pushes south and east on Sunday as the cold front becomes positioned over the Deep South. Farther north, a reinforcing shot of cooler air from Canada ushering in a swath of showers and some storms across the Great Lakes today reaches the Northeast by Sunday afternoon. This system will attempt to merge with one of the aforementioned waves of low pressure reaching the Mid-Atlantic coast by late Sunday and produce a period of strong to possibly severe thunderstorms near the Mid-Atlantic coast. By Monday, high pressure is in control from the Midwest to the Northeast while scattered thunderstorms set up shop along the Gulf Coast. In the West, a ridge of high pressure aloft has anchored itself over the region and continues to generate excessive heat this afternoon across the interior Pacific Northwest. An influx of monsoonal moisture being advected in from the Southwest should cool down temps in the interior Pacific Northwest on Sunday. Speaking of monsoonal moisture, there is no shortage of it across the drought-stricken Intermountain West. However, there is such a deep reservoir of monsoonal moisture available that showers and thunderstorms are capable of producing heavy rainfall rates and could trigger areas of flash flooding. Locations most at risk for flash flooding are where antecedent soil conditions are overly saturated or near burn scars. As a result, a handful of Slight risks for Excessive Rainfall are in place from the Great Basin to the central Rockies today. The Excessive Rainfall threat on Sunday shifts a into areas such as Bitterroots and Snake River Valley as well as the southern High Plains. More rounds of heavy showers and storms are possible up and down the spine of the Rockies on Monday. Lastly, Air Quality Alerts remain in effect for portions of Montana, Wyoming, Minnesota, Wisconsin, Iowa, and the Tennessee Valley due to smoke associated with raging wildfires over western North America being advected into the regions by prevailing north-northwesterly winds. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php