Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 250 AM EST Wed Dec 16 2015 Valid 12Z Wed Dec 16 2015 - 12Z Fri Dec 18 2015 ...Freezing rain possible for interior portions of Oregon and Washington State... ...Heavy rains possible over parts of the Pacific Northwest and into parts of Northern California... ...Snow possible over parts of the Upper Mississippi/Upper Great Lakes... ...Heavy rain over parts of the Southern Appalachians... A storm over the Upper Mississippi Valley will move northeastward into Northern Ontario by Thursday evening. The associated front extends from the Upper Mississippi Valley southward to the Lower Mississippi Valley that will move eastward to the East Coast by Thursday evening. Showers and thunderstorms will develop over Lower Mississippi Valley/Central Gulf Coast that will move east to parts of the Southeast by Thursday. Rain will develop along the boundary from the Upper Mississippi Valley/Upper Great Lakes to the Middle Mississippi Valley that will likewise move eastward to the Northeast/Southern Mid-Atlantic by Thursday evening. In addition, snow will develop over parts of the Upper Mississippi Valley/Upper Great Lakes on Wednesday into Thursday morning. Meanwhile, upper-level energy over the Pacific Northwest will move southeastward to the Southern Plains by Thursday evening. Onshore flow will aid in producing rain along the Pacific Northwest Coast into parts of Northern California through Wednesday evening. Snow and lower elevation rain will develop over parts of interior Northwest and over parts of the Northern Intermountain Region/Northern Rockies through Thursday morning. Scattered rain and higher elevations snow will develop over parts of the Central Rockies on Thursday with rain moving over parts of the Central Plains by Thursday evening. Additionally, warmer air and weak upper-level impulses will move inland over the Pacific Northwest on Wednesday evening into Thursday evening. Snow levels will rise over the Northwest while some of the cold air will be trapped in the valleys that will lead to areas of rain/freezing rain Wednesday night into Thursday morning. By Thursday evening enough warm air will move into the valleys that the precipitation will be all rain. Higher elevation snow and rain will also develop over parts of the interior Northwest on Wednesday night and expand into parts of the Northern Intermountain Region on Thursday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php