Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 229 PM EST Fri Dec 23 2016 Valid 00Z Sat Dec 24 2016 - 00Z Mon Dec 26 2016 ...Flooding rains possible tonight across 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... An expansive storm system moving into the western U.S. this afternoon will make for an eventful holiday weekend across much of the Nation. Through tonight, the system will produce widespread rainfall across much of the West Coast, with snow at the higher elevations. The heaviest precipitation through tonight is expected to fall across portions of southern California, where heavy rain and even a few thunderstorms may produce flooding for some areas. Heavy snow will also be possible tonight in the Sierras. On Saturday, the system will move east, spreading snow into the Great Basin, Intermountain West, and the Rockies. Snow is expected to begin spreading into the northern High Plains by late Saturday. 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. Late Saturday night into Sunday the system will begin to emerge from the Rockies into the High Plains, where a surface cyclone is forecast to quickly deepen. Snow is forecast to quickly spread across most of the northern High Plains by Sunday morning, with an area of freezing rain possible in the transition zone from rain to snow across the Midwest. Heavy snow and strong, gusty winds are possible. Blizzard conditions are possible across portions of the northern plains on Christmas Day, where snow along with winds gusting in excess of 60 mph could create very dangerous travel conditions. Please refer to products issued by local NWS Forecast Offices for details specific to your area. Farther south, the system is expected to produce showers and thunderstorms in the warm sector on Sunday. Some thunderstorms could be severe on Sunday across portions of the central plains. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Farther east, a rather fast-moving and weak frontal system will bring areas of snow and mixed precipitation from the Great Lakes to the Northeast tonight and Saturday, with rain and a few thunderstorms from the lower/mid-Mississippi valley to the Mid-Atlantic. In the wake of this system, generally warm conditions will prevail across much of the central and eastern U.S. into the weekend. Afternoon high temperatures are forecast to be 5 to 15 degrees above average on Saturday from the plains to the East Coast. 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. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php