Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 242 PM EST Thu Dec 28 2017 Valid 00Z Fri Dec 29 2017 - 00Z Sun Dec 31 2017 ...Heavy snowfall likely in the higher terrain of the northern Intermountain West and northern Rockies... ...Arctic air will overtake much of the central U.S. by this weekend... A cold front pushing onshore early tomorrow morning in the Pacific Northwest will allow for widespread precipitation across much of the Northwest U.S. and into the northern Rockies. Winter weather advisories and winter storm warnings from Washington to Montana are highlighting the potential for heavy snowfall, with as much as 2 to 3 feet possible in the highest terrain of the Washington Cascades and the northern Rockies. Some minor freezing rain accumulations are also possible in the lower elevations of central Washington and northeast Oregon. Heavy rainfall can be expected for coastal regions of the Pacific Northwest as well. Light snowfall will spread from the Dakotas and the Upper Midwest tomorrow into parts of the Mid-Atlantic and Northeast by Saturday as a clipper type system moves through. Light accumulations may be possible across parts of the northern Plains and Upper Midwest, with little to no accumulation expected as the system pushes into the Northeast. Westerly flow on the backside of the system will also allow for continued lake effect snowfall downwind of the upper and lower Great Lakes. Some moderate accumulations are possible. The big story with this front however will be a surge of very cold arctic air plunging southward into the central U.S. by this weekend. Temperature anomalies on Saturday could be as much as 30 to 35 degrees below normal with afternoon highs of below zero expected across parts of the northern Plains. Meanwhile, a wavy stationary boundary in the Gulf of Mexico will keep mainly light showers across the Gulf Coast and Southeast states the next couple of days. Much of this should be rainfall but a shallow layer of cold air east of the Appalachians may allow for freezing rain or a rain/snow mix across portions of Georgia and the Carolinas on Friday. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php