Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 324 PM EDT Sun Aug 08 2021 Valid 00Z Mon Aug 09 2021 - 00Z Wed Aug 11 2021 ...Heavy rain and severe storms possible in the Midwest and Great Lakes through Tuesday, with the threat of severe weather returning to the Northern Plains on Monday... ...Above average temperatures and oppressive humidity found across the central U.S., shifting into the Northeast by Tuesday... ...Poor air quality due to wildfire smoke found throughout parts of the High Plains and West... Much of the active weather to close out this second weekend of August and start a new workweek will be located across the Midwest, Great Lakes, and Northern Plains. Two separate upper-level disturbances are expected to traverse these regions and spark numerous showers and the thunderstorms. The first system is currently located over the Upper Midwest and in conjunction with a weakening frontal boundary extending eastward across the Upper Great Lakes. Developing thunderstorms this evening may turn severe between southern Missouri and Wisconsin, producing damaging wind gusts, large hail, isolated tornadoes, and frequent lightning. Flash flooding will also be a concern across this area, with upwards of 2+ inches of rain possible where repeating rounds of thunderstorms occur. Flash Flood Watches are in effect across central Wisconsin. By Monday, the next impulse of energy and associated cold front is expected to enter the Northern Plains and spark scattered thunderstorms across parts of the Central/Northern Plains, with a greater chance of damaging wind gusts and large hail found across the eastern Dakotas. As the cold front continues to swing east on Tuesday, organized showers and thunderstorms are expected to return to the Great Lakes and Midwest. Elsewhere, monsoonal moisture could bring continued rounds of thunderstorms to parts of southern Arizona, while typical summertime storms impact parts of the Florida Panhandle and the Ohio Valley. For many residents east of the Rockies, the dog days of summer have arrived as heat and high humidity swelter much of the country. Above average temperatures found across the Great Plains and Upper Midwest will lead to highs into the upper 90s, with triple digits possible throughout the central and southern High Plains. The combination of warm temperatures and oppressive humidity is expected to lead to heat indices above the century mark on Monday and Tuesday across the middle and lower Mississippi Valleys. August heat will also be found throughout the Lower Great Lakes and shift into the Mid-Atlantic and Northeast early this week. Highs here are forecast to reach into the 90s, while heat indices approach 100 degrees. Meanwhile, a building heat wave is expected to reach the Pacific Northwest by Tuesday, with much hotter weather forecast to enter the region by midweek. Excessive Heat Watches has been issued. Wildfire smoke continues to produce poor air quality for much of the western U.S. as well. Widespread Air Quality Alerts and scattered Red Flag Warnings stretch from the Northwest and Northern Rockies to the High Plains, as well as throughout parts of central California. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php