Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 331 PM EDT Fri Jun 18 2021 Valid 00Z Sat Jun 19 2021 - 00Z Mon Jun 21 2021 ...Severe thunderstorms and flash flooding are likely throughout the Ohio Valley and Midwest this evening... ...Tropical downpours and an increasing threat for dangerous flash flooding will spread into the Central Gulf Coast region this evening and into portions of the Southeast this weekend... ...A long-duration heat wave will continue across a large portion of the western United States... Much of the Ohio Valley and into sections of the Midwest could see damaging thunderstorms and flash flooding this evening/overnight. A slow moving cold front draped across the Great Lakes and into the Central Plains will be the focus for thunderstorm activity. Warm temperatures and an abundance of atmospheric moisture will lead to potent thunderstorms and the capability of intense rainfall rates. The Storm Prediction Center has issued an Enhanced Risk (level 3/5) of severe weather from southern Iowa to Ohio. Damaging wind gusts and isolated tornadoes will be the main concern across the Ohio Valley, with large hail most likely to impact parts of the Midwest near southern Iowa and northern Illinois. Meanwhile, multiple rounds of heavy rain and downpours are likely to lead to flash flooding concerns overnight between southern Indiana to southern/central Ohio. WPC has issued a Moderate Risk (level 2/4) of Excessive Rainfall throughout this region due to multiple inches of rain possible in a very short amount of time. This threat of severe thunderstorms and heavy rain will drastically decrease on Saturday, but isolated showers and thunderstorms are still expected between the Ohio Valley and Northeast. Farther south, a low pressure system in the Gulf of Mexico (currently labeled as Potential Tropical Cyclone Three) is forecast to slowly push northward and into the Central Gulf Coast tonight. The biggest impacts with this system will be associated with heavy rain and flash flooding. Rainfall totals of 4 to 8 inches with isolated maximum amounts of 12 inches are possible between eastern Louisiana and the western Florida Panhandle. This amount of rain will likely lead to considerable flash, urban, and small stream flooding impacts, as well as new and renewed minor to isolated moderate river flooding. Once the system lifts into the southeastern U.S. this weekend, rainfall amounts of 3 to 5 inches with isolated maximum amounts of 7 inches are possible. WPC has issued a Moderate Risk of Excessive Rainfall for tonight across coastal sections of southeast Louisiana, Mississippi, and Alabama. A Moderate Risk of Excessive Rainfall also exists on Saturday throughout central/southern Alabama and portions of western/central Georgia. A few isolated tornadoes are possible across southern Alabama and the Florida Panhandle on Saturday as well. By Sunday, much of the associated impacts will lessen and spread into the Carolinas. An oppressive, dangerous, and long-duration heat wave will continue through at least the beginning of the weekend in the West. Well above and potentially record-breaking temperatures will be found throughout the Southwest, California, and Central Great Basin this evening and Saturday. By Sunday, temperatures begin to relax slightly, but will still remain above average. Excessive Heat Warnings and Heat Advisories are still in effect across much of California, Nevada, Arizona, Utah, and sections of western Colorado and northern New Mexico. Red Flag Warnings have also been issued in order to highlight the fire danger associated with the ongoing heat and extremely dry soils. Elsewhere, above average temperatures and summer heat will be felt throughout the central/southern Plains and Middle Mississippi Valley this weekend ahead of an approaching cold front. This same frontal boundary will fuel numerous showers and thunderstorms across the northern/central Plains on Saturday and Upper Midwest by Sunday. A few thunderstorms could turn severe in the central High Plains on Saturday. Behind the cold front, cool and pleasant temperatures will rush into the north-central United States. Snell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php