Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 519 PM EDT Thu Aug 26 2021 Valid 00Z Fri Aug 27 2021 - 00Z Sun Aug 29 2021 ...The potential for flash flooding and severe weather continues across portions of the Northern Plains and Midwest... ...Heavy rain and flooding possible for the Mid-Atlantic Friday... ...Uncomfortable and potentially dangerous heat continues throughout much of the central and eastern United States, as well as the Desert Southwest... A persistent frontal system as well as a shortwave trough moving across the Northern Tier of the U.S. will continue to lead to the chance of heavy rain, flooding, and severe weather across portions of the Northern Plains and Midwest. A quasi-stationary front draped from the Lower Great Lakes westward through Nebraska should begin to lift slowly northward as a warm front throughout the day Friday. Widespread showers and thunderstorms are expected overnight tonight along the boundary and will continue on Friday. There is a Slight Risk (level 2 of 4) for excessive rainfall Friday for portions of southeastern Minnesota and central Wisconsin as another 2 to 4 inches of rain are expected on top of the heavy rain that has already fallen. Additionally, the Storm Prediction Center has issued a Slight Risk (level 2 of 5) for severe weather for northern Iowa, southeastern Minnesota, and central Wisconsin as isolation south of the boundary will help support more robust thunderstorms with the threat of large hail and high winds. The shortwave approaching from the west on Friday will also help to begin to push the frontal system eastward across the Northern High Plains, and thunderstorms are expected to develop along and ahead of the front. The Storm Prediction Center has issued a Slight Risk of severe weather for portions of southeastern Montana and the western Dakotas mainly for the threat of large hail. As the shortwave and frontal system continue east, thunderstorms are expected to develop again on Saturday with another Slight Risk highlighted by the Storm Prediction Center for portions of southern Minnesota into northwestern Wisconsin. Further east, a cold front will push southward through the Northeast on Friday and begin to stall across the Mid-Atlantic Friday evening. There is a Slight Risk of excessive rainfall for Friday from eastern Pennsylvania and northern Maryland east into central and northern New Jersey. Showers and storms along the boundary may produce a couple inches of rain over a region with recently saturated soils due to heavy rain from Henri. Showers and storms will continue on Saturday as the front remains quasi-stationary. Heat will also be a major story throughout the forecast period. Ahead of the fronts, highs in the mid- to upper 90s are forecast from the Mid-Atlantic and Carolinas west through the Ohio Valley, Mississippi Valley, and into the Central Plains on both Friday and Saturday. High humidity will lead to heat indices closer to 100. Temperatures will also rise into the 90s over the Great Lakes region on Saturday. There will be little relief from the heat at night as lows are expected to remain well above normal and only fall into the low to mid-70s. In the Desert Southwest, highs in the 110s are expected on Friday, and an Excessive Heat Warning remains in effect for the area through Friday evening. The high temperatures will cool a little on Saturday but still generally be in the upper 100s to lower 110s. Elsewhere, showers and storms are likely along the Gulf Coast as moisture increases ahead of T.D. Nine, which is forecast by the National Hurricane Center to move northwestward into the Gulf of Mexico. Some Monsoonal showers and storms are also possible across Arizona and New Mexico on Saturday. Putnam Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php