Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 243 AM EST Mon Dec 12 2016 Valid 12Z Mon Dec 12 2016 - 12Z Wed Dec 14 2016 ...Wintry weather possible for portions of the lower Great Lakes, Mid-Atlantic, and Northeast... ...Heavy snow possible across portions of the Intermountain West and northern Rockies... ...Stream of Pacific moisture to bring heavy rain and snow to portions of the West Coast Tuesday and Wednesday... A deepening low pressure system will move from the Great lakes into southern Ontario and Quebec today. Ahead of the low, widespread wintry weather will affect areas from the lower Great Lakes to the Northeast and portions of the Mid-Atlantic regions today. A mix of snow, sleet, and freezing rain is possible. Heavy snow will be possible for some areas.Farther south, rain will fall from the southern Mid-Atlantic region to the Southeast and Tennessee valley. Conditions will improve across the Mid-Atlantic and Northeast by late today as the low pressure system quickly moves east into the Canadian Maritimes. The trailing end of the associated cold front will stall along the Gulf Coast, and will begin moving northward again as a warm front on Tuesday, keeping rain and a few thunderstorms a possibility from the Gulf Coast to the Southeast into Wednesday. An arctic frontal boundary will continue to produce snow today across portions of the northern Rockies and northern Intermountain West. Snowfall may be heavy for some areas. Heavy snow will also be possible early this morning for the Cascades, although snowfall should begin to taper off and become more scattered in nature by afternoon. Late Tuesday night into Wednesday, a Pacific low pressure system will begin to spread a substantial area of precipitation into portions of central/northern California. Heavy rain will be possible, with heavy snow at the higher elevations in the Sierras. This stream of Pacific moisture will continue to affect the West Coast into Wednesday, with the potential for heavy rain and snow persisting. Lastly, another arctic air mass will overspread much of the northern plains and Midwest over the next couple days. High temperatures today are forecast to be 20 to 30 degrees below average across portions of the northern plains. These cold temperatures will spread east into the Midwest for Tuesday and Wednesday. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php