Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sun Aug 01 2021 Valid 12Z Sun Aug 01 2021 - 12Z Tue Aug 03 2021 ...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... A cool air mass will continue to make steady progress through the central and eastern portions of the country today to offer relief to the recent spell of oppressive heat. Showers and thunderstorms will signal the arrival of the cooler air across the central Plains to the Tennessee Valley today behind a cold front with multiple low pressure waves. Hot and very humid conditions will persist for one more day today across the Deep South where Heat Advisories and some Excessive Warnings are currently in effect. By Monday, more widespread showers and thunderstorms will keep temperatures at bay through the Deep South as the front edges closer from the north. Meanwhile, a reinforcing cold front will spread showers and some thunderstorms across the lower Great Lakes today and into northern New England tonight. This system will attempt to merge with low pressure wave forecast to develop today across the Carolinas to help trigger a period of strong to possibly severe thunderstorms near the Mid-Atlantic coast. A cool and dry air mass across the northern Plains will be ushered into the central U.S. and the Northeast behind the front to begin the new work week. Over the Mid-Atlantic region however, the front is forecast to stall later on Monday which will encourage the rain to linger and possibly redevelop near the Carolina coast Monday night as another low pressure wave is forecast to develop. 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 the interior Northwest, Arizona, Colorado, the upper Midwest, the Tennessee Valley and South Carolina due to smoke associated with wildfires over western North America being transported into the regions. Kong/Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php