Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Thu Mar 30 2017 Valid 12Z Thu Mar 30 2017 - 12Z Sat Apr 01 2017 ...Severe thunderstorm potential through Thursday over the Middle/Lower Mississippi and Tennessee Valleys... ...Heavy snow likely for the Northern/Central Rockies, Great Basin and Wasatchs... ...Heavy rain for portions of the Pacific Northwest and the Lower/Middle Mississippi Valley... Widespread showers and thunderstorms are forecast for much of Mississippi Valley Region as a robust low pressure system tracks across the Midwest and through the Tennessee/Ohio valley today . The Storm Prediction Center continues to identify conditions favorable for severe thunderstorms development across much of the Ohio valley southward to the Gulf Coast. The highest threat will extend from the southern half of Illinois and Indiana and Ohio across the western Tennessee Valley and Central Mississippi, generally in the region nearest to the approaching cold front and associated lift/instability. Additionally, some of these storms may produce heavy rainfall; which may increase the threat for flash flooding. Refer to SPC's Convective Outlooks and WPC's Excessive Rainfall Outlooks for specific details. This system is expected to reach the Appalachians/Mid-Atlantic region by Friday morning and will usher in showers and thunderstorms to much of the Eastern Seaboard beginning tonight. A mix of rain and snow may develop over parts of the Upper Great Lakes today and tonight, while a wintry mix of rain, snow, and ice is expected across the northeast starting tonight and continuing over the next couple of days. Upper-level energy will continue to dig southward across the western U.S. today and tonight. At the surface, a series of low pressure system and frontal features will continue their trek inland, reaching the western edge of the Central and Northern Rocky Mountains by this afternoon/evening. It will then continue eastward splitting into a northern U.S. system and a south central U.S. system after passing over the Rocky mountains Friday/Friday night. The southern stream system is expected to impact the southern and central Plains region through the weekend. A stream of moist onshore flow will result in rain and higher elevation snow for the Pacific Northwest inland into the Central and Northern Rockies by this afternoon/evening, with snow expected to continue overnight. Snow, potentially heavy, will persist across the highest elevations of the Northern/Central Rockies and the northern portion of the Great Basin Friday night into Saturday. Wix/Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php