Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 318 AM EST Sun Dec 27 2020 Valid 12Z Sun Dec 27 2020 - 12Z Tue Dec 29 2020 ...Heavy snow possible for parts of the Sierra Nevada Mountains and the Central Rockies... ...Snow for the Great Lakes... ...A strong storm to impact Southern California to the Plains on Monday into Tuesday... Low pressure over the Middle Mississippi Valley will move northeastward to Eastern Canada by Tuesday. The associated front will move from the Southern/Central Plains to off the East Coast by Tuesday morning. As the system moves out of the Northern High Plains, snow is already ongoing over parts of the Northern Rockies and the Northern Plains on Sunday morning. By Sunday afternoon, snow will develop over the Upper Mississippi Valley/Upper Great Lakes and parts of the Middle Mississippi Valley, while rain develops over parts of the Western Ohio Valley into parts of the Middle/Lower Mississippi Valley. The heaviest snow will develop over Wisconsin before sunset on Sunday. Rain and snow move into the Lower Great Lakes and Northern Ohio Valley on Monday morning, while rain moves into the Southern Ohio/Tennessee Valleys. On Monday evening, rain and snow move into parts of the Northeast, while snow continues over parts of the Great Lakes. The snow will taper off to light lake effect snow downwind from Lakes Superior, Huron, Erie, and Ontario by Tuesday morning. The storm will produce 4 to 6 inches of snow over parts of the Wisconsin and Michigan. The snow will aid in creating hazardous driving conditions over the region. Meanwhile, a front over the Pacific will move onshore over California overnight Sunday, moving eastward to the Central/Southern Rockies by Tuesday. Rain and higher elevation snow will develop over parts of Central California overnight Sunday. On Monday morning, snow will develop over parts of the Great Basin into parts of the Central Rockies. Snow will develop over parts of the Southwest on Monday evening. Overnight Monday, snow will develop over parts of the Northern/Central Plains and parts of the Southern Rockies. Also, overnight Monday, the snow and rain will start to taper over California. Rain will also develop over parts of the Southern/Central Plains with pockets of rain/freezing rain over parts of the Central Plains by Tuesday morning. Snowfall amounts of 12 to 18 inches will develop over parts of the Sierra Nevada Mountains and 24 to 30 inches over parts of the Central Rockies. The snow and freezing rain will aid in producing dangerous driving conditions. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php