Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 246 AM EST Wed Nov 21 2018 Valid 12Z Wed Nov 21 2018 - 12Z Fri Nov 23 2018 ...Heavy rain possible for parts of California and the Pacific Northwest... ...Heavy snow possible for the Sierras/Cascades and parts of the Northern/Central Rockies... ...There is a marginal risk with embedded slight risk of excessive rainfall over parts of California ...Temperatures will be 10 to 25 degrees below average over the Northeast... A front extending from the Lower Great Lakes to the Middle Mississippi Valley then northwestward into the Northern High Plains will move southeastward off the most of the Eastern Seaboard by Thanksgiving evening. A stationary front will extend from the Southeast Coast northwestward to the Northern High Plains on Thanksgiving. The system will produce snow over the Great Lakes into parts of Northern New England that will move off the Northeast Coast by Thanksgiving morning. In the wake of the storm very cold high pressure will southeastward from Western Ontario to the Northern Mid-Atlantic by Thanksgiving evening. Temperatures will be 10 to 25 degrees below average from the Great Lakes to the Northeast and Mid-Atlantic States from Thursday evening into Friday. Meanwhile, upper-level energy over the New Mexico/Mexican border will move eastward to the Southeast by Thanksgiving evening. The energy will produce light rain over parts of the Western Gulf Coast that will expand eastward into parts of the Central Gulf Coast by Thanksgiving morning before ending over the Western/Central Gulf Coast by afternoon on Thanksgiving. An important story, a deep upper-level trough will move onshore over the West Coast on Wednesday moving inland to the Rockies overnight Thursday. Rain will begin to develop along the West Coast on Wednesday morning and move inland to the Northern/Central Rockies and the Great Basin by Thanksgiving evening. The rain will be heavy over parts of Northern California into the Pacific Northwest Coast through Friday morning. Heavy snow will develop over the higher elevations of the Sierras and the Cascades with heavy rain at the lowest elevations. Due to the heavy precipitation, a marginal with embedded slight risk of excessive rainfall is issued over California from Wednesday morning into Friday morning. Overnight Wednesday, rain and higher elevation snow will develop over parts of the Northern Intermountain Region and the Great Basin that will expand into the Northern/Central Rockies overnight Thursday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php