Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EST Wed Dec 25 2019 Valid 00Z Thu Dec 26 2019 - 00Z Sat Dec 28 2019 ...There is a Slight Risk of excessive rainfall over parts of Southern/Central California... ...Heavy snow for mountains of Southern California, Southwest, and Southern Rockies... ...Temperatures will be 15 to 30 degrees above average from the Great Lakes/Ohio Valley into parts of the Southern Plains... A low over the Middle Mississippi Valley will move northeastward to James Bay by Friday. The system will produce rain and snow over parts of the Upper Mississippi Valley/Upper Great Lakes into parts of the Northern/Central Plains on Christmas night. By Thursday evening the snow moves into Southern Canada while the rain moves into the Lower Great Lakes. Overnight Thursday, rain/freezing rain and snow will move into parts of Northern New England, followed by rain into New England into Friday evening. A deep upper-level trough and upper-level low will move over parts of Southern California on Christmas night moving into parts of Southern Rockies by Friday evening. Ahead of the system, mountain snow and lower elevation rain will develop over part of the Great Basin Central/Southern Rockies and the Southwest with the percipitation waning by late Thursday afternoon. As the energy moves onshore, rain and higher elevation snow will develop over Southern California on Thursday morning. Embedded convection may enhance rainfall rates right along the coast from Santa Barbara through Los Angeles into San Diego. Snowfall over a foot is possible in the mountains in Los Angeles and Ventura counties. The precipitation will spread across the Colorado River on Thursday into the lower deserts of Arizona but with lower amounts toward the Phoenix and Tucson areas. Some modest snowfall is likely for northern Arizona along the Mogollon Rim. The rest of the lower 48 will see relatively dry and mild conditions with temperatures near normal along the New England coast but up to 25 degrees above normal in the Middle Mississippi Valley into the Great Lakes/Midwest. Some record highs are possible today and tomorrow. A frontal boundary will waver over the Central Plains through the Corn Belt and Great Lakes today and will lift northward on Thursday, spreading generally light precipitation (rain along the boundary, mix to the north, snow to the northwest) toward the east-northeast. Below normal temperatures are forecast for much of the West and especially the Southwest due to the incoming front. Expect temperatures only in the mid 50s to low 60s for southern California and the lower deserts of Arizona. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php