Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 433 AM EDT Sun May 21 2017 Valid 12Z Sun May 21 2017 - 12Z Tue May 23 2017 ...There is a slight risk of severe thunderstorms over parts of the Lower Rio Grande Valley... ...Heavy rain possible from portions of the Southeast to the Central/Western Gulf Coast... Low pressure over the Upper Mississippi Valley/Upper Great Lakes will slowly move northward into Ontario on Monday. The associated front will become quasi-stationary from the Lower Great Lakes to Central Appalachians/Tennessee Valley to the Western Gulf Coast through Monday. The system will produce showers and thunderstorms from the Upper Great Lakes to the Ohio/Tennessee Valleys into the Lower Mississippi Valley and Southern Plains that will move eastward to the Mid-Atlantic/Southeast to the Central/Western Gulf Coast by Monday evening into Tuesday. An area of showers and thunderstorms will develop over parts of the Southeast through Monday morning. Rain will also develop over parts of the Upper Mississippi Valley that will move into parts of the Upper Great Lakes overnight Sunday into Monday evening. Meanwhile, upper-level energy the Great Basin/Northern Intermountain Region will move southeastward to the Southern Rockies by Monday evening. Additional upper-level energy will move southward out of West-Central Canada on Sunday evening moving to the Central Plains by Monday evening. The energy coming out of Canada will begin to induce a front over parts of the Middle Missouri Valley to the Southern High Plains by Monday evening. The first area of energy will produce rain with embedded thunderstorms over parts of the Great Basin that will expand eastward to the Central Rockies and northward into the Northern High Plains by Sunday evening. The rain with embedded showers/thunderstorms will extend into the Southern High Plains overnight Sunday. Showers and thunderstorms will develop along the developing boundary from parts of the Middle Mississippi Valley southwestward to the Southern High Plains by Monday evening. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php