Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 219 PM EST Mon Dec 05 2016 Valid 00Z Tue Dec 06 2016 - 00Z Thu Dec 08 2016 ...Severe thunderstorms and heavy rain possible for portions of the Southeast and lower Mississippi valley... ...Heavy snow possible for portions of the northern plains and Upper Midwest, as well as the Pacific Northwest... ...Cold air expected to spread across much of the Rockies and the Great Plains... A strengthening low pressure system in the northern Gulf of Mexico will continue to spread rain and thunderstorms across much of the Southeast and lower Mississippi valley through tonight. Some areas from the lower Mississippi valley to the Southeast could see a threat of severe thunderstorms as well as heavy rain/flash flooding. As the surface low moves northeastward to the Tennessee valley on Tuesday, precipitation will spread farther north into the Ohio valley, Mid-Atlantic, and the Northeast. Cold air in place on the northern periphery of the system will allow some precipitation to fall as a mix of rain, sleet, and snow from the northern Mid-Atlantic region into the Northeast. Rain will begin to come to an end across the Southeast by Tuesday afternoon, but areas of rain and snow will persist across the Northeast into Wednesday morning as the low pressure system moves out into the open Atlantic Ocean. An area of low pressure is forecast to continue deepening across the Upper Midwest this evening. The system will bring snow to areas from the northern plains into the Upper Midwest through tonight and into Tuesday. Heavy snow snow along with gusty winds are possible for some areas, resulting in the potential for some blowing and drifting snow. Snow will begin to taper off by Tuesday afternoon as the low pressure system moves northeast into Ontario, however scattered snow showers will persist into Wednesday. Onshore flow will continue to spread moisture and precipitation into the Pacific Northwest through tonight. Cold air in place across the region will allow precipitation to fall as snow even in valleys, with some accumulations possible. Across the higher terrain of southeastern Oregon, including the southern Cascades and Coastal Range, heavy snow is possible. An Arctic cold front will spread a frigid air mass southward into the Rockies and much of the plains through midweek. Afternoon highs on Tuesday are forecast to be 20 to 30 degrees below average from the northern Rockies into the northern High Plains. On Wednesday these cold temperatures will spread south into the central Rockies and the central plains. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php