Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 420 PM EDT Sat Apr 18 2020 Valid 00Z Sun Apr 19 2020 - 00Z Tue Apr 21 2020 ...Widespread flash flooding and severe weather are expected on Sunday across the Lower Mississippi Valley into the Southeast... The synoptic pattern across the U.S. will continue to support an active storm track across the southern tier states. Moisture currently returning from the Gulf of Mexico will interact with a frontal boundary along the Gulf Coast as an upper-level trough moves into the southern Plains. This will result in a low pressure wave to develop and intensify along the frontal boundary as the wave tracks rapidly across the Deep South toward the Carolina coasts through Monday. Sunday should turn out to be a very active day in terms of heavy rain and severe weather from central Mississippi eastward into South Carolina where over 3 inches of rain could fall over areas that have received above normal rainfall over the past few weeks. This will exacerbate the flooding and flash flooding threats in these areas. The low pressure wave is forecast to further intensify and move rapidly off the East Coast during the day on Monday, pushing the rain out into the Atlantic by the afternoon. Elsewhere, a cold front will bring mainly light precipitation across the northern Plains into the Great Lakes into tonight, followed by the Northeast and the Mid-Atlantic on Sunday, and then into the Atlantic on Monday. A frontal system ahead of a low pressure system tracking across southern Canada will bring another round of light precipitation across the Great Lakes on Monday. Meanwhile, wintry mixed precipitation is forecast to track across the interior Northwest toward the northern and central Rockies into Monday morning where snowfall of a few inches are expected in parts of the northern Rockies. The Four Corners region could also receive a couple rounds of light precipitation over the next couple of days under a broad upper trough. Temperature-wise, generally cooler than normal temperatures can be expected across a good portion of the Plains, Mississippi Valley, and Ohio Valley north of a cold front. In contrast, temperatures will rebound in Texas on Sunday as a warm front lifts northeastward across the area. The Florida peninsula should remain hot with scattered thunderstorms. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php