Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 244 PM EST Fri Dec 13 2024 Valid 00Z Sat Dec 14 2024 - 00Z Mon Dec 16 2024 ...Heavy snow over the Sierra Nevada Mountains, highest peaks of the Cascades, and the Northern Intermountain Region on Friday evening into Saturday; Heavy snow over parts of the Northern Rockies on Saturday evening into Sunday... ...0.10 inches of rain/freezing rain over parts of the Middle Mississippi Valley on Friday evening into Saturday and the Northern High Plains/Central Appalachians on Saturday evening into Sunday†â€Patchy rain/freezing rain over parts of the Upper Mississippi Valley and Great Lakes on Saturday evening into Sunday... ...There is a Slight Risk of excessive rainfall over parts of Northern California... A front extending from the Central Plains to the Southern High Plains will move eastward and dissipate by Sunday, while the associated upper-level energy moves into the Great Lakes/Ohio Valley. Return flow off the Gulf of Mexico will start to stream northward over parts of the Southern Plains, producing showers and thunderstorms over parts of the Southern Plains and Middle/Lower Mississippi Valley overnight Friday into Saturday. In addition, rain will move into the Ohio and Tennessee Valleys on Saturday evening into Sunday. Additionally, overnight Friday, as the moisture streams farther northward over the Mississippi Valley, rain/freezing rain will develop over parts of the Middle Mississippi Valley. Light snow will develop slightly farther north over parts of the Upper Mississippi Valley. Overnight Saturday into Sunday, rain/freezing rain will develop over parts of the Central Appalachians. Rain will also move into parts of the Mid-Atlantic on Sunday. Furthermore, easterly flow off the Atlantic will aid in producing light rain from the Southern Mid-Atlantic Coast to the Florida coast on Saturday into Sunday. Meanwhile, a front moving onshore over the Pacific Northwest/Northern California will move eastward to the Northern/Central Plains and Southern High Plains by Sunday. The system will produce rain and higher-elevation snow over the Pacific Northwest and Northern California overnight Friday. The rain and higher-elevation snow will expand into Central California and the Northern Intermountain Region on Saturday. The snow will be heavy over the Sierra Nevada Mountains, the highest peaks of the Cascades, and the Northern Intermountain Region on Friday evening into Saturday. Moreover, moisture streaming onshore over Northern California will produce heavy rain over parts of the state. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall through Saturday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable, as well as landslides on roads. Likewise, moisture will continue to flow into Northern California, producing heavy rain. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall from Saturday through Sunday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and low-lying areas the most vulnerable, as well as landslides on roads. Overnight Saturday into Sunday, heavy snow will develop over parts of the Northern Rockies as the front moves into the Northern High Plains. Further, rain/freezing rain will develop over parts of the Northern High Plains. By Sunday evening, there will be a break in the precipitation over the Pacific Northwest/Northern California. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php