Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 318 PM EST Sun Dec 21 2014 Valid 00Z Mon Dec 22 2014 - 00Z Wed Dec 24 2014 ...A winter storm should affect the Northern Plains/Upper Midwest region... ...Heavy rainfall expected along the Olympics and Cascades... ...Severe weather possible on Tuesday along the Central/Eastern Gulf Coast... The upper pattern entering next week will become of higher amplitude with a strong trough digging into the center of the country. Initial impulses currently racing across the Upper Intermountain West will help carve out a pronounced closed low across the Middle Mississippi Valley by Monday evening. This will be the focus for unsettled weather over the Northern Plains and Upper Midwest where wintry precipitation is expected. The system at hand is not forecast to get the best moisture support given a boundary along the Gulf Coast will rob some of the incoming moisture transport. However, the upper system is expected to be slow moving which should allow a longer time for snowfall accumulations. The WPC winter weather graphics suggest a widespread axis of 4 to 6 inches of snow anywhere from South Dakota eastward into Minnesota and Northern Wisconsin/Upper Peninsula of Michigan. Heavy precipitation along the west coast will persist with a focus along the Coastal Ranges and Washington/Oregon Cascades. Strong onshore flow will transport anomalous moisture inland with heavy rainfall affecting the windward slopes of the local topography. While not nearly as impressive as recent days, the forecast suggests another 1 to 3 inches of rainfall across the region. Looking farther inland, moderate to heavy snow is likely over the Wasatch and Colorado Rockies with 1 to 2 foot amounts possible through Monday. This is in response to strong lift with the mid-level energy passing overhead in conjunction with enhanced vertical motions along the surging cold front. Given the strong upper trough anchoring the center of the country, a well defined cold front will advance eastward in time with convection breaking out along and ahead of it. Some of the thunderstorms may become severe along the Central/Eastern Gulf Coasts on Tuesday based on the latest Storm Prediction Center outlook. A wet period is being forecast from the southeastern states up along the I-95 corridor. A stalled frontal boundary has continued to drive active convection across the southeastern U.S. Gradually a wave of low pressure will lift along the East Coast which will help carry light to moderate rainfall toward the Mid-Atlantic region. Locations on the far western end of the precipitation shield may see periods of freezing rain given favorable thermodynamic profiles. This is primarily the case over the Central Appalachians where boundary layer temperatures will remain below freezing. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php