Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Wed Jul 28 2021 Valid 12Z Wed Jul 28 2021 - 12Z Fri Jul 30 2021 ...There is a Moderate Risk of severe thunderstorms over parts of the Upper Mississippi Valley, Upper Great Lakes, and parts of the Ohio Valley through Thursday morning... ...There is a Slight Risk of excessive rainfall over parts of the Upper Mississippi Valley/Upper Great Lakes through Thursday morning... ...There is a Slight Risk of excessive rainfall over parts of the Southwest Thursday into Friday morning... ...Heat Advisory over parts of the Mississippi Valley and the Plains; Excessive Heat Warning over parts of the Northwest... A front extending from the northern Mid-Atlantic across the Ohio Valley into the Upper Midwest will have a wave of low pressure traveling along the boundary through Thursday. As a result, showers and thunderstorms will develop along and near the boundary through Thursday evening. Some of these thunderstorms will become severe with more robust dynamics. Therefore, the SPC has issued a Moderate Risk of severe thunderstorms over parts of Upper Great Lakes through Thursday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. There is a 10% or greater probability of wind gust of 65 knots or greater and a 10% or greater probability of two-inch or great hail over parts of the Upper Mississippi Valley/Upper Great Lakes through Thursday morning. Furthermore, there is a 10% or greater probability of EF2-EF5 over parts of the Upper Mississippi Valley/Upper Great Lakes through Thursday morning. Additionally, the thunderstorms will produce heavy rain. Therefore, the WPC has issued a Slight Risk of excessive rainfall with these thunderstorms over parts of the Upper Mississippi Valley, Upper Great Lakes, and parts of the Ohio Valley through Thursday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable. Showers and thunderstorms will continue along and near the boundary through Friday. The severe thunderstorm threat shifts to the Ohio Valley, Mid-Atlantic, Central Appalachians, and Northeast Thursday into Friday morning. The excessive rainfall threat decreases slightly on Thursday into Friday morning. Meanwhile, showers and thunderstorms will continue over the Southwest, Central/Southern Rockies, and Great Basin today, though the excessive rainfall threat will be lower. However, the monsoonal moisture streams back into the Southwest as strong upper-level energy passes over the region Thursday into Friday. Therefore, the WPC has issued a Slight Risk of excessive rainfall over the Southwest on Thursday into Friday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable. Over the Northwest, there is an Excessive Heat Warning over parts of the area, where temperatures will be above average. Furthermore, Heat Advisories are currently in effect for portions of the Mississippi Valley and the Plains where the temperatures will be 10 to 20 degrees above average. Moreover, several regions have Air Quality Alerts due to wildfires over the Northwest into the Northern Rockies. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php