Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 356 AM EDT Mon Aug 09 2021 Valid 12Z Mon Aug 09 2021 - 12Z Wed Aug 11 2021 ...Heavy rain and severe storms possible in the Midwest and Great Lakes through Tuesday; severe weather returns to the Northern Plains today... ...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... A wave of low pressure tracking through the Northern Plains will become the main driver in producing strong-to-severe storms in the Dakotas later today. The Storm Prediction Center has issued a Slight Risk in the portions of the eastern Dakotas and northwest Minnesota. Farther east, a second wave of low pressure tracking along a warm front in the Midwest is set to generate its own area of showers and thunderstorms, some of which could be severe. Heavy rainfall rates are also likely within the strongest storms, especially in the Great Lakes where there is ample atmospheric moisture available. By Tuesday, the Northern Plains system heads north into south central Canada, but the warm sector becomes positioned across the Midwest and Great Lakes. The storm's accompanying cold front will act as a trigger for severe thunderstorms Tuesday afternoon and evening with damaging winds and large hail possible. By Tuesday night, including Monday night's rainfall, parts of the Midwest and Great Lakes could receive 2-3 inches of rainfall with higher amounts in more localized areas. Areas of showers and thunderstorms are also likely to transpire in other regions as well through the first half of the work-week. The Ohio and Tennessee Valleys can expect daily episodes of thunderstorms, some of which could become severe and/or cause flash flooding. Daily hit-or-miss showers and storms will also be possible in parts of the Southeast both Monday and Tuesday. Also, spotty showers and storms are on tap from the Mid-Atlantic to the Northeast on Tuesday. In the Southwest, monsoonal moisture arrives with scattered showers and thunderstorms potentially causing areas of flash flooding. The South-Central and Northwestern U.S. can expect mostly dry conditions into mid-week. Meanwhile, the dog days of summer have arrived as sultry conditions engulf much of the country. Above average temperatures are focused in the Great Plains and Upper Midwest with triple digit temperatures, as well as some daily record high temps, possible in the central and southern High Plains. The combination of abnormally hot temperatures and oppressive humidity is expected to cause heat indices to exceed the century mark on Monday and Tuesday across the middle and lower Mississippi Valleys. Stifling heat will also be found across the Lower Great Lakes, the Mid-Atlantic, and Northeast the first half of the week. High temps are forecast to reach into the 90s, while heat indices approach 100 degrees. Farther west, a building heat wave is expected to reach the Pacific Northwest by Tuesday with considerably hotter weather forecast to overtake the region by midweek. Excessive Heat Watches have been issued in advance of this impending heat wave. Last but certainly not least, wildfire smoke continues to produce poor air quality for much of the western U.S.. Numerous Air Quality Alerts and scattered Red Flag Warnings stretch from the Northwest and central California to the Rockies and the High Plains. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php