Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EST Sun Dec 01 2024 Valid 00Z Mon Dec 02 2024 - 00Z Wed Dec 04 2024 ...More heavy lake-effect snow expected through the next couple of days across the Great Lakes... ...A reinforcing shot of polar air from Canada will bring a period of light snow from the northern Plains to the southern Appalachians followed by colder temperatures through the next couple of days... ...Showers and thunderstorms will be edging closer toward the lower Texas coast through the next couple of days... ...Temperatures will be 10 to 15 degrees below average over parts of the northern Plains to the Ohio Valley, into the Mid-Atlantic and the Southeast... A synoptic pattern that favors broad upper-level troughing in North America will continue to periodically usher polar air from Canada into the eastern two-thirds of the country while relatively mild and dry weather persists across the western U.S. The leading edge of the next surge polar air is currently dipping into the northern High Plains. A period of light snow is expected to spread from the northern Plains, across the Midwest, Ohio Valley and then into the southern Appalachians ahead of a wave of low pressure forming along the cold front. An arctic high pressure system behind the front will usher colder air into these areas, bringing temperatures of 10 to 15 degrees below average. In the mean time, light snow across the central and southern Appalachians is expected to taper off into tonight. As the relatively cold air flows over the relatively warm waters of the Great Lakes, more lake-effect snow can be expected across the Great Lakes, although they should be less active for parts of the recently harder-hit locations as the wind direction turns more southwesterly. Locally a couple of feet of new snow is possible downwind from Lake Michigan and Lake Erie through the next couple of days. Meanwhile, moisture has been gradually gathering in the western Gulf of Mexico to the south of Texas along a convergence zone where a low pressure wave is forecast to form over the next couple of days. As the wave begins to interact with colder air filtering from the north, scattered showers and thunderstorms are expected to gradually expand and edge toward the lower Texas coast and into southern Texas through Tuesday. Elsewhere, upper-level ridging over the western U.S. will create stagnant air conditions over the valley locations from interior California into the Pacific Northwest, leading to areas of dense fog and poor air quality. Kong Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php