Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 351 PM EST Fri Dec 25 2015 Valid 00Z Sat Dec 26 2015 - 00Z Mon Dec 28 2015 ...Flash flooding possible across portions of the central and eastern U.S... ...Heavy snow possible tonight from portions of the northern Rockies to the Upper Midwest... ...Major winter storm expected Saturday and Sunday from the southern Rockies to the southern plains... A nearly stationary frontal boundary will bring widespread showers and thunderstorms to areas from the lower and middle Mississippi valley to the Mid-Atlantic and the Lower Great Lakes tonight into Saturday. This system has a history of producing heavy rain and flooding/flash flooding over much of the southeastern U.S., and the threat for excessive rainfall will continue. Flash flooding will be possible tonight from the lower Mississippi valley to portions of the Mid-Atlantic. The flash flooding threat will shift a little northward on Saturday, from portions of the southern plains, to the middle Mississippi valley and into the Lower Great Lakes. An upper-level disturbance will move from the northern Rockies into the northern plains tonight. This disturbance, along with sufficient cold air north of an arctic cold front will result in snow this evening through tonight from the northern Rockies eastward into the northern plains and parts of the Upper Midwest. Snowfall amounts of 5 to 10 inches are forecast over portions of this area. The system will move into the Upper Great Lakes on Saturday, with lighter snowfall amounts generally in the 2 to 5 inch range. This system will bring snow to northern Maine as well by late Saturday night into Sunday, with 5 to 10 inches of snow forecast for central and northern Maine. An upper-level trough will deepen into a very intense upper-level low across the southwestern U.S. tonight into Saturday. Heavy snow will begin to develop early Saturday morning across the higher terrain of New Mexico. Through the day on Saturday, an area of low pressure at the surface will develop near the Rio Grande in western Texas, as an arctic cold front sweeps in from the north. The surface low will pull additional moisture into the system, and widespread wintry precipitation is expected to expand from New Mexico into much of western Texas by Saturday evening. A mix of snow, sleet, and freezing rain is likely in the transition zone between snow and rain. By Sunday morning the snow, sleet, and freezing rain will expand northeast across the southern plains. Heavy snowfall amounts of 10 to 18 inches are forecast through Sunday evening across much of western/northwestern Texas, with 18 to 24 inches forecast across portions of New Mexico. Additionally, strong winds resulting from the rapidly deepening low pressure system may result in possible blizzard conditions for some areas. Please refer to products issued by local NWS Forecast Offices for details specific to your area. Additionally, in the warm sector of this storm system, from eastern Texas into the lower Mississippi valley, severe thunderstorms will be possible on Saturday and Sunday. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Lastly, a Pacific low pressure system will approach the Northwest on Sunday, spreading rain and mountain snow into the region through Sunday night. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php