Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 357 PM EDT Thu Jul 18 2019 Valid 00Z Fri Jul 19 2019 - 00Z Sun Jul 21 2019 ...A dangerous heat wave is building in the central and eastern U.S.... ...Severe weather and flash flooding are both possible for the Upper Midwest this evening... An upper-level ridge is building over the southeastern U.S., setting the stage for what will be a miserably hot and humid weekend for millions of Americans. The sprawling area of high pressure will drive hot and humid air north and east from the Gulf through the Northeast. Daytime temperatures will soar into and through the 90s from the Plains eastward, and overnight minimums in the 70s and 80s will provide little relief. Heat Advisories, Excessive Heat Watches, and Excessive Heat Warnings are in effect for the Plains, Mississippi and Ohio Valleys, and the Eastern Seaboard. Dozens of record high minimum temperatures are forecast to be set across the eastern U.S., and a handful of record high maximum temperatures will be challenged. The heat wave is expected to persist through the weekend across the east, but a cold front ushering in cooler air will march across the U.S. as an upper-level trough begins to build near Hudson Bay. Scattered thunderstorms are expected along fronts moving through the north-central U.S., a few of which could be severe and produce heavy rainfall. Slight Risks of both severe weather and excessive rainfall are in place this evening for parts of the Great Lakes region, with more storms possible across the Upper Midwest tomorrow. Today, a Slight Risk for excessive rainfall remains for the northern Mid-Atlantic, tied to moisture from the remnants of Barry. Elsewhere, the trough responsible for the cooler temperatures and lower relative humidity in the Northwest will also raise concerns for fire weather conditions throughout the Intermountain West. Nettesheim Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php