Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 744 AM EST Thu Nov 22 2018 Valid 12Z Thu Nov 22 2018 - 12Z Sat Nov 24 2018 ...Heavy rain likely in parts of California through Saturday which could lead to flash flooding, mudslides, and debris flows over recent burn scars... ...Heavy snow possible for the Sierras/Cascades and parts of the higher elevations of the Great Basin/Northern Intermountain Region as well as the Northern/Central Rockies... ...Temperatures will be 20 to 35 degrees below average from the Great Lakes/Mid-Atlantic into the Northeast... A deep upper-level trough over the West Coast will move inland to the Mississippi Valley by Saturday night. The system will produce rain and higher elevation snow over parts of the Pacific Northwest/California into Northern Intermountain Region/Great Basin on Thanksgiving. The rain will end over Southern California by Thursday evening as the snow and lower elevation rain expands into parts the Northern/Central Rockies and continue over the region into Saturday. The rain will be heavy over Northern/Central California with heavy snow over the Cascades/Sierras, Northern Intermountain Region/Great Basin, and Northern/Central Rockies, likewise, through Saturday. Meanwhile, a very cold area of high pressure over the Great Lakes will move southeastward off the Mid-Atlantic Coast by Friday evening. Temperatures will be 20 to 35 degrees below average from the Great Lakes/Mid-Atlantic into the Northeast, with temperatures beginning to moderate by Friday evening. As the aforementioned upper-level trough moves out of the Rockies, moisture from the Western Gulf of Mexico will move northward over the Plains into the Upper Mississippi Valley/Upper Great Lakes by Friday evening. By Friday afternoon, rain will develop over parts of the Upper Mississippi Valley southward to the Western Gulf Coast. The rain will expand into the Great Lakes/Ohio Valley and the Central/Southern Appalachians as well as into parts of the Southeast/Eastern Gulf Coast. Overnight Friday, areas of rain/freezing rain will develop over parts of the Central/Southern Appalachians. In addition, snow will develop over parts of the Upper Mississippi Valley overnight Friday, too. Additionally, easterly flow off the Atlantic will aid in streaming moisture inland over parts of Southeast by Thursday evening. The moisture will aid in producing showers and thunderstorms over parts of Florida overnight Thursday into Friday evening. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php