Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 313 PM EST Sat Jan 07 2017 Valid 00Z Sun Jan 08 2017 - 00Z Tue Jan 10 2017 ...Snow...heavy at times...across the Mid-Atlantic and New England coasts this evening is expected to taper off later tonight... ...Arctic air will overspread much of the eastern two-thirds of the country... ...An extended period of heavy rain and snow is expected across much of the western U.S. into next week. A low pressure system deepening rapidly off the Mid-Atlantic coast will move northeastward towards Nova Scotia on Sunday. A large swath of snow is currently spreading northeastward from the Mid-Atlantic states into coastal New England. As the low pressure system continues to rapidly intensify off the East Coast, winds near the coast will continue to strengthen as the snow becomes heavy, especially over southeastern New England where blizzard conditions could occur tonight before the storm moves further away early on Sunday. Interior sections of the East Coast may not see any snow at all. In the wake of this storm system, arctic air will overspread much of the eastern two-thirds of the country through the weekend, with high temperatures more than 20 degrees below normal near the Mid-Atlantic coast on Sunday. Temperatures will moderate somewhat in the central and southern Plains on Sunday as a reinforcing surge of arctic air moves into the northern Plains. Light snow and snow showers will accompany the associated arctic front. Out West, an extended period of stormy weather is in the forecast as a series of Pacific fronts and energetic low pressure systems bring an onslaught of precipitation through the weekend and into next week. Heavy rain is possible across California, with flooding possible in northern California. Snow, heavy at times, will fall over the Sierras and the Coastal Ranges and initially over the lower elevations of coastal Oregon and Washington. Snow levels will gradually rise, with all but the highest elevations of the Sierras changing to rain this evening. Cold air will remain trapped at some of the lower elevations near the coast in Oregon and Washington through early Sunday morning, keeping snow or freezing rain in place for some areas. Widespread snow, heavy for some areas, will also overspread much of the interior West through Sunday, including the Intermountain West and Great Basin as well as the central and northern Rockies. As warmer Pacific air spreads inland, snow levels will also rise across these areas, with precipitation changing to rain across much of the Great Basin by Sunday night. As a cold front moves inland Sunday night, rain will once again change back to snow across interior portions of the Pacific Northwest. By Monday, snow will continue to linger over much of northern and central Rockies, as another reinforcing surge of arctic air spreads a swath of light snow from across the northern Plains eastward into the upper Midwest. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php