Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 328 PM EST Tue Dec 19 2017 Valid 00Z Wed Dec 20 2017 - 00Z Fri Dec 22 2017 ...Heavy snow possible over the Southern Cascades... ...Snow over the Northern/Central Rockies, Northern Plains, and Great Lakes... ...Heavy rain possible over parts of the Lower Mississippi Valley into the Tennessee Valley/Southern Appalachians... Upper-level energy over Texas will move eastward off the Southern Mid-Atlantic Coast by early Thursday morning. Moisture from the Western Gulf of Mexico will move inland over the Western Gulf Coast/Lower Mississippi Valley and into parts of the Southeast through Wednesday evening. Rain and thunderstorms will develop over parts of the Southern Plains into the Lower Mississippi Valley/Tennessee Valley that will expand eastward into the Southern Mid-Atlantic by Wednesday morning. The rain and thunderstorms will come to an end, west to east, starting Wednesday morning into Thursday. Meanwhile, a strong upper-level trough over the Northwest will move southeastward to the Great Basin/Southwest by Thursday. The energy will aid in producing rain and higher elevation snow over the Pacific Northwest and snow over the Northern Intermountain Region/Northern Rockies. Overnight Tuesday, rain and higher elevation snow will expand into parts of Northern California and Central California by Wednesday afternoon. Snow will also expand into the Great Basin and the Northern High Plains also overnight Tuesday. The rain and higher elevation snow will begin to end over the Pacific Northwest by Wednesday evening and over parts of the Northern Rockies/Great Basin by Thursday. In addition, light snow will move into the Northern Plains on Wednesday morning and move into the Upper Mississippi Valley/Upper Great Lakes by Thursday. The snow will also expand into parts of the Central Rockies/Southwest overnight Wednesday into Thursday. Elsewhere, upper-level energy moving across the Great Lakes into Northern New England will move out over the Western Atlantic by Wednesday evening. The energy will aid in developing light snow over parts of the Upper Great Lakes into New England that will slowly taper off to lake effect snow over the Upper Great Lakes by Wednesday morning. By Wednesday evening, the lake effect snow will come to an end. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php