Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EST Thu Dec 12 2013 Valid 00Z Fri Dec 13 2013 - 00Z Sun Dec 15 2013 ...Winter storm to impact parts of the Midwest, northern Appalachians and New England with snow and ice... ...Heavy lake effect snow showers to end, only to be followed by more snow from an approaching storm system this weekend... ...Warm up coming for the northern High Plains... The big story over the lower 48 will be with a developing storm system which should begin to take shape over the Southern Plains and Mississippi Valley on Friday. At the surface, bitter cold temperatures currently remain north of an arctic front draped across the northern tier of the United States, but as an upper level disturbance emerges into the Southern Plains from the Southwest on Friday, the cold air across the North will begin to quickly sag southward with the leading edge reaching West Texas by Friday evening. Meanwhile, warm and moist air from the Gulf of Mexico will advect northward ahead of the surface low with light showers transitioning into a steady moderate rain by Friday night in the Lower Mississippi Valley. With sub freezing temperatures still in place at the surface, light freezing rain is expected with the onset of precipitation Friday morning across portions of the Ozarks along the northern fringes of the precipitation shield. Overrunning light to moderate snow will expand north and east Friday night into Saturday across the Midwest and Ohio Valley with several inches possible by the time snowfall ends on Saturday. Locations across the Gulf Coast States should see a steady rainfall with embedded thunder at times, especially for southern portions of the region. Cold air will be banked along and east of the Appalachians as the storm system makes its way east on Saturday with a wintry mix likely for locations from Washington, D.C. to Philadelphia and New York. The details are still being ironed out, but interior sections of the Northeast should see a significant snowfall from this storm system by the time the weekend is over. Localized heavy snows downwind of Lakes Erie and Ontario are forecast to come to an end with the passage of a cold front tonight, which will disrupt the low level wind fetch across the lakes and preventing band organization. More scattered in nature snowfall is anticipated with the frontal passage with light accumulations possible before the aforementioned storm system approaches. Out over the western U.S., as mid level ridging attempts to build back in across the West Coast, a downslope flow regime should set up over the northern High Plains. The result will be gusty winds with high temperatures steadily rising from Friday through the weekend. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php