Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 254 AM EST Sat Dec 24 2016 Valid 12Z Sat Dec 24 2016 - 12Z Mon Dec 26 2016 ...Flooding rains possible through early Saturday morning for portions of coastal southern California... ...Significant winter storm possible over the holiday weekend from the Rockies to portions of the northern plains and Upper Midwest... ...Above average temperatures expected for much of the central and eastern U.S... Much of the U.S. will be impacted this holiday weekend by a robust winter storm system that will track across the Rockies and through the Plains states into the Upper Midwest and Great Lakes region. Widespread rain, heavy at times, has been observed overnight across portions of southern California as the front moved inland. Rain and the threat for flash flooding will linger into the morning hours. Widespread snow will spread into the Great Basin, Intermountain West, and the Rockies today and into the northern High Plains by late afternoon/evening. Heavy snow will be possible, especially at the higher elevations of the West. Rain is expected to fall at the lower elevations in the Southwest and Four Corners regions. Most counties west of the continental Divide and across eastern Montana have winter weather advisories and winter storm warnings in effect. Most of the Dakotas have blizzard warnings in effect. Once the system exits the Rockies and moves out over the Plains, the surface low will quickly deepen. Strong winds, possibly in excess of 60 mph, will cause snow to blow and drift, making travel hazardous - especially across the northern-tier states. Please refer to products issued by local NWS Forecast Offices for details specific to your area. Thunderstorms will be possible along and ahead of the front moving through the central Plains on Sunday and Monday. Some thunderstorms could be severe - please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Areas of snow and mixed precipitation is possible from the Great Lakes to the Northeast, with rain and a few thunderstorms from the lower/mid-Mississippi valley to the Mid-Atlantic today. Once the weakening system passes through temperatures will warm up across the central and eastern states. Afternoon high temperatures are forecast to be 5 to 15 degrees above average on today. By Sunday, as warmer air is pulled north across the plains ahead of the rapidly deepening cyclone, high temperatures may reach 15 or more degrees above average for many areas of the plains, Ohio and Tennessee valleys, and the Southeast. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php