Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 349 AM EDT Thu Jul 18 2019 Valid 12Z Thu Jul 18 2019 - 12Z Sat Jul 20 2019 ...A widespread and dangerous heat wave is building in the central and eastern U.S.... ...Severe weather and flash flooding are both possible for the Upper Midwest to Upper Great Lakes today... As an upper-level ridge builds, a heat wave is forecast to spread across the central and eastern U.S. High temperatures in the 100s are expected for the Southern and Central High Plains, with 90s widespread farther east. Where temperatures are in the 90s, high dewpoints will create dangerous heat indices, and Excessive Heat Warnings and Watches and Heat Advisories are in effect for much of the Plains, Mississippi and Ohio Valleys, and the Eastern Seaboard. Overnight low temperatures will not provide much relief, with values in the mid to upper 70s to even 80 degrees. Dozens of high minimum temperature records are forecast to be set, with a few record high maximum temperatures possible as well. The heat wave is expected to persist over the weekend beyond the short range period. Meanwhile, the West Coast and Northwest should see below average temperatures behind a cold front. Fronts moving slowly across the north-central U.S. will lead to scattered thunderstorms there over the next couple of days. Storms could contain locally heavy rain, which may lead to flash flooding. Slight Risks of both severe weather and excessive rainfall are in place on Thursday across portions of the Upper Midwest to Upper Great Lakes. Elsewhere, rain and thunderstorms are possible in parts of the Mid-Atlantic and Northeast today as tropical moisture formerly associated with Barry combines with a front in the vicinity. Scattered thunderstorms are possible farther south into the Southeast over the next couple of days, and isolated storms could also affect the Southwest to Southern High Plains. Tate Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php