Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 358 AM EDT Mon Jun 20 2016 Valid 12Z Mon Jun 20 2016 - 12Z Wed Jun 22 2016 ...There is a slight risk of severe thunderstorms from the Lower Great Lakes to the Middle Mississippi Valley... ...Heavy rain possible over parts of the Central Appalachians and parts of the Middle Mississippi Valley... A front extending from the Great Lakes to the Central Plains then westward into the Central Rockies will move eastward to the Northeast/Mid-Atlantic Coast then westward to the Central Plains by Tuesday evening. Showers and thunderstorms will develop along and ahead of the boundary over parts of the Upper Great Lakes into the Middle Mississippi Valley by Monday morning that will extend from just off the Northeast Coast into the Mid-Atlantic then westward to the Central Plains by Tuesday evening. Meanwhile, upper-level energy moving onshore over the Pacific Northwest on Monday evening will move inland to the Northern High Plains by Tuesday evening/Wednesday morning. A wave of low pressure will develop over parts of Northern High Plains on Tuesday morning. Rain will develop over parts of the Pacific Northwest on Tuesday morning ending by Tuesday evening. Showers and thunderstorms will develop along the associated developing front over the Northern High Plains into the Central Rockies/Central High Plains on Tuesday afternoon into Tuesday evening. In addition, onshore flow off the Western Gulf of Mexico and on the Southeastern Coast of Florida along with daytime heating will aid in producing showers and thunderstorms over the Central/Western Gulf Coast and southern Florida through Tuesday evening/Wednesday. With a daytime heating component, the areal coverage of the Showers and thunderstorms will be greatest during the afternoon and evening hours. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php