Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 324 PM EST Wed Dec 18 2013 Valid 00Z Thu Dec 19 2013 - 00Z Sat Dec 21 2013 ...Temperatures will be 10 to 15 degrees above average from the Central Appalachians to the Southern High Plains... ...Temperatures will be 15 to 25 degrees below average over the Northern High Plains/Northern Plains... Front over the Upper Midwest will move to the Northeast across the Great Lakes/Ohio Valley to the Southern Plains by Friday. Waves of low pressure will move along the boundary from the Plains to the Great Lakes. Ahead of the system, lake effect snow will develop over the Upper Great Lakes through Thursday morning. Moisture from the Gulf of Mexico will move northward over the Mississippi Valley into the Ohio Valley Thursday into Friday morning. Rain will develop over parts of the Middle Mississippi Valley by Thursday evening, expanding into the Ohio/Tennessee Valleys to the Central Gulf Coast by Friday. Snow will develop over parts of the Great Lakes into Northern New England by Friday morning. A narrow band of rain/freezing rain will develop over parts of the Lower Missouri Valley Thursday night into Friday. In addition, showers and thunderstorms will develop over parts of the Western Gulf Coast and the Lower Mississippi Valley also by Friday morning. Meanwhile, upper-level energy over Western Canada will dive southward along the West Coast to Southern California/Northern Mexico, forming an upper-level closed low by Friday. Scattered light snow will develop over the higher elevations of the Pacific Northwest into parts of the Northern Rockies by Wednesday evening. The snow will move into parts of the Great Basin/Central Rockies by Thursday morning. Additionally, high pressure over West-Central Canada will move southeastward to the Northern Plains by Friday. The circulation around the high will produce upslope flow developing snow over the Northern High Plains on Wednesday evening moving into the Northern Plains by Thursday evening before ending on Friday morning. The upper-level energy over Southern California will induce a front over the Southwest into Mexico on Thursday. Rain will develop over parts of Southern California on Thursday moving into the lower elevations of the Southwest/Southern Rockies and the Lower Rio Grande Valley by Friday morning. Snow will also develop over the higher elevations of the Sierras and the Southwest Thursday into Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php