Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 321 AM EDT Mon May 09 2016 Valid 12Z Mon May 09 2016 - 12Z Wed May 11 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 late Monday into Tuesday... Southerly winds ahead of an upper system moving out of the central Rockies into the Great Plains are forecast to draw warm, moist air from the Gulf of Mexico -- supporting widespread showers and thunderstorms across the lower and central Great Plains into the lower and mid Mississippi valley Monday into Monday night. Some of these storms 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. Moisture spreading further to the north is likely to 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. On Tuesday into early Wednesday, the previously noted upper system is forecast to weaken as it continues to track to the east. Organized showers and thunderstorms are expected to focus along the frontal boundary that will continue to extend from the mid Mississippi into the Ohio valley and Mid-Atlantic states. Back to the west, a well-defined cold front is forecast to drop through the western U.S. this period, with below-average temperatures spreading south and east from the northern Rockies and High Plains. Moderate to heavy precipitation is likely to develop west of an organizing area of low pressure over the northern High Plains. Heavy rain accumulations are expected to center over eastern Montana, with heavy mountain snows over the ranges of southwestern Montana and northwestern Wyoming. Pereira Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php