Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 347 AM EDT Mon May 17 2021 Valid 12Z Mon May 17 2021 - 12Z Wed May 19 2021 ...There is a Moderate Risk of severe thunderstorms over parts of Southern Plains... ...There is a Slight Risk of excessive rainfall over parts of the Central High Plains and the Central Gulf Coast... A quasi-stationary front extends from the Middle Mississippi/Western Ohio Valleys westward to the Central/Southern High Plains, then into the Great Basin through Wednesday morning. A dryline will develop over parts of the Southern High Plains, making a daily oscillation eastward. Moisture from the Western Gulf of Mexico will stream northward over the Plains and the Mississippi Valley that will help produce showers and thunderstorms over parts of the Central/Southern Plains and Middle/Lower Mississippi Valley through Wednesday. The SPC has issued a Moderate Risk of severe thunderstorms over parts of Southern Plains through Tuesday morning. The main threats from the severe thunderstorms are frequent lightning, severe thunderstorm wind gust, hail, and a few tornadoes. Additionally, there is a 10% or greater probability of two-inch or greater hail over the Southern High Plains. The WPC has issued a Slight Risk of excessive rainfall over parts of the Central High Plains and the Central Gulf Coast through Tuesday morning. The heavy rain associated with the thunderstorms will produce localized areas of flash flooding. The most vulnerable areas to the heavy rain are urban areas, roads, and small streams. Showers and thunderstorms will also develop over parts of the Ohio Valley into the Central Appalachians/Mid-Atlantic on Monday. On Tuesday, the severe thunderstorm threat and the excessive rainfall threat will continue over the Southern Plains into parts of the Lower Mississippi Valley. Rain will develop over parts of the Upper Mississippi Valley/Upper Great Lakes into Wednesday morning. Meanwhile, overnight Monday, a front will move onshore over the Pacific Northwest, moving inland to the Northern Plains to the Great Basin/Southern California by Wednesday. Light rain will develop over the Northwest with wet snow at the highest elevations through Wednesday morning. Elsewhere, light rain with embedded thunderstorms will develop over parts of the Northeast through late Tuesday evening. Easterly flow off the Atlantic will aid in producing showers and thunderstorms over the east coast of Florida on Tuesday into Wednesday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php