Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 449 AM EDT Sat May 11 2013 Valid 12Z Sat May 11 2013 - 12Z Mon May 13 2013 ...Slight risk of severe thunderstorms today for portions of the Southeast and Mid-Atlantic states... ...Heavy snow possible tonight and early Sunday morning across portions of the Upper Great Lakes... ...Unseasonably cold temperatures expected for much of the central and eastern U.S... A deep upper-level trough will dig across the central and eastern U.S. today in to Sunday. A couple cold fronts will move eastward across the same areas today. Behind the second cold front, an unseasonably cold air mass will move into much of the north central and northeastern U.S. Showers and thunderstorms will be possible today in the warm and relatively humid air mass ahead of the fronts. The Storm Prediction Center is forecasting a slight risk for severe thunderstorms today and tonight for portions of the Southeast and Mid-Atlantic states. For more information on the severe weather potential, please refer to the Convective Outlooks issued by the Storm Prediction Center. The threat for thunderstorms will end by Sunday morning as the leading cold front moves offshore into the Atlantic Ocean. Farther north, snow is forecast tonight into early Sunday morning across the Great Lakes as cold air pushes into the region and a strong upper-level disturbance moves overhead. There is the potential for some heavy snow, primarily across the Upper Peninsula of Michigan. A ridge of high pressure at the surface and aloft will largely dominate the weather during the short range across the interior western U.S. However, a Pacific frontal system will approach the Northwest tonight with the potential for rain showers and possibly a few thunderstorms. Precipitation across the Northwest should become a little less widespread later on Sunday as the front pushes inland. Temperatures across the western U.S. will remain generally above average through the short range forecast period. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php