Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 407 PM EDT Mon May 09 2016 Valid 00Z Tue May 10 2016 - 00Z Thu May 12 2016 ...Strong to severe thunderstorms possible from the southern and central Great Plains to the lower and mid Mississippi Valley... ...Heavy rainfall accumulations possible for portions of the Midwest and northern High Plains... ...Locally heavy snows possible for portions of the northern Rockies into Tuesday... Warm, moist air transporting northward from the Gulf of Mexico is fueling the convection ahead of low pressure system crossing the southern Plains and low pressure system that is moving from the Central Rockies into the central Great Plains. Scattered to widespread showers and thunderstorms spanning from the northern High Plains to the lower and mid Mississippi Valley will continue through night and into Tuesday. Cooler air will stream in along the northern Rockies and northern High Plains as the cold front pushes through. Periods of heavy rain are expected across the eastern half of Montana, which will increase the threat for flash flooding and river flooding. An excessive rainfall outlook has been issued for this area. Some of the storms in the southern and central plains may be strong to severe, particularly from northeast Texas, southeast Oklahoma into Arkansas and northwest Louisiana, where the air mass is expected to become highly unstable as well. The Storm Prediction Center has identified this area as having an enhanced risk for severe thunderstorms. Moisture spreading further to the north will likely focus along a slow moving frontal band -- supporting widespread moderate to locally heavy rainfall accumulations across portions of the lower Missouri and mid Mississippi valleys. Excessive rainfall will be possible through Tuesday morning from Arkansas northeastward to the southeast Iowa and western Illinois. Organized showers and thunderstorms are expected to focus along the frontal boundary that will continue to extend from the mid Mississippi valley into the Ohio valley and Mid-Atlantic states. Campbell/Pereira Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php