Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 345 PM EST Tue Nov 21 2017 Valid 00Z Wed Nov 22 2017 - 00Z Fri Nov 24 2017 ...Heavy rain possible over the Pacific Northwest... ...Rain changing to snow over parts of the Lower Great Lakes... A front extending from the Lower Great Lakes roughly southwestward to the Lower Mississippi Valley/Southern Plains will move east and southward to off the Eastern Seaboard and the Gulf Coast by Wednesday. An area of rain and snow over parts of the Great Lakes will move eastward into Northern New England by Wednesday evening and into Canada by late Wednesday night. In the wake of the front, lake effect snow will develop for a short time over parts of the Upper Great Lakes on Tuesday evening, ending by Wednesday afternoon. Meanwhile, areas of disorganized upper-level energy over the Southeast and the Southern Plains will aid in producing showers and thunderstorms over parts of the Western/Eastern Gulf Coast and parts of the Southeast through Wednesday morning. The first bundle of energy will move off the Southeast Coast overnight Tuesday inducing an area of low pressure off the Carolina Coast just ahead of the cold front. The low will become a wave of low pressure along the front over the Western Atlantic that will move northeastward into the Canadian Maritimes overnight Wednesday. Overnight Tuesday, the energy will develop rain over parts of the Carolinas into the Mid-Atlantic that will move northward into Southern New England by Wednesday morning and into Northern New England by Wednesday afternoon. The rain will move off the New England Coast by Wednesday evening. The second are of upper-level energy will move to the Eastern Gulf Coast and, likewise, develop a wave of low pressure along the boundary over the Eastern Gulf of Mexico overnight Wednesday into Thursday. The energy will produce showers and thunderstorms over parts of Florida Wednesday evening into Thursday, Thanksgiving. Elsewhere, a plume of moisture from the Pacific will stream into the Pacific Northwest that will continue until Thursdsay, Thanksgiving, as the axis of moisture moves southward into Northern California also on Thanksgiving. The moisture will aid in producing rain over parts of the Pacific Northwest eastward into parts of the Northern Rockies through Thursday, Thanksgiving. In addition, rain will move into parts of Northern California Coast overnight Wednesday into Thanksgiving. Furthernmore, a fast moving area of low pressure over the Northern High Plains Wednesday morning, will move eastward to the Upper Great Lakes by Thanksgiving morning, Thursday. An area of light snow will develop over parts of the Upper Mississippi Valley/Northern Plains on Wednesday afternoon that will move to the Upper Great Lakes by Thursday morning, Thanksgiving. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php