Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 356 AM EST Sat Dec 26 2015 Valid 12Z Sat Dec 26 2015 - 12Z Mon Dec 28 2015 ...Flash flooding likely across portions of the central and eastern U.S... ...Heavy snow possible from portions of the High Plains to the Upper Midwest... ...Major winter storm expected this weekend from the southern Rockies to the southern plains... A vast area spanning from southeast Wyoming to northern Michigan will have snow through Sunday as an upper-level disturbance tracks across the Plains. Numerous Winter Storm Warnings and Advisories are in effect with this system; widespread heavy snow is expected as the disturbance passes through the arctic airmass. The heaviest swath is anticipated to occur from southern Minnesota to northern Michigan where accumulations will range from 10 to 15+ inches. As this system continues on its eastward track snow will spread across the Great Lakes and into the Northeast Sunday and Monday. 5 to 10 inches of snow is forecast for central and northern Maine. Winter Storm Warning and Advisories are in effect across northern Vermont and New Hampshire, including most of Maine. A large portion of central Conus and along the Applachaians will continue to have widespread showers and thunderstorms this weekend along an advaning low pressure system. 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 persist. Flash flooding will be possible today from the Southern Plains, the middle Mississippi Valley and into the Lower Great Lakes region -- remaining over the Southern Plains and middle Mississippi Valley for Sunday. An upper-level trough will deepen into a very intense upper-level low across the southwestern U.S. Heavy snow will begin across the higher terrain of New Mexico today. An area of low pressure will spin up 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 tonight. 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. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php