Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EST Wed Dec 11 2024 Valid 00Z Thu Dec 12 2024 - 00Z Sat Dec 14 2024 ...Heavy lake-enhanced snow downwind from the Great Lakes on Wednesday evening into Thursday; light lake-effect snow downwind from most of the Great Lakes on Friday; light to moderate snow over parts of the Sierra Nevada Mountains on Wednesday into Friday... ...Moderate to heavy lake-effect snow downwind from Lake Ontario on Friday... ...Temperatures will be 15 to 25 degrees below average over parts of the Northern Plains and Upper Mississippi Valley... ...There is a Slight Risk of excessive rainfall over parts of New England... A deep upper-level trough over the Upper Midwest to the Mid-Atlantic weakens slightly while upper-level energy continues to move across the Great Lakes through Friday. The system will produce heavy lake-enhanced snow downwind from the Great Lakes Wednesday evening into Thursday. Overnight Thursday into Friday, the lake-enhanced snow will become light lake-effect snow downwind from most of the Great Lakes. However, moderate to heavy lake-effect snow will develop downwind from Lake Ontario on Friday. Additionally, a front along the Northeast Coast will move quickly out over the Western Atlantic by late Wednesday night. Rain will develop along the boundary over most of the East Coast, ending from the Mid-Atlantic southward overnight Wednesday. Over New England, the rain will change over to light snow overnight Wednesday into Thursday. The system will produce heavy rain over parts of New England. Therefore, the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over parts of New England through Thursday 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. On Wednesday, high pressure over Central Canada will move southeastward to the Great Lakes and Mid-Atlantic by Friday evening. Cold air associated with the high will move over the Upper Midwest, bringing temperatures 15 to 25 degrees below average over parts of the Northern Plains and Upper Mississippi Valley. The cold weather has prompted Cold Weather Advisories over parts of North Dakota, Minnesota, and Wisconsin. Meanwhile, another front over the Eastern Pacific will move onshore over California by early Thursday, dissipating as the boundary moves from Southern California into Mexico overnight Thursday. The system will produce coastal rain and higher elevation snow over parts of the Pacific Northwest and Northern California overnight Wednesday into Thursday. On Thursday, the rain and higher-elevation snow will move into Central California, producing light snow over the Sierra Nevada Mountains over the next few days. On Friday, another front over the Eastern Pacific will move onshore over parts of the Northwest and California. The storm will produce more coastal rain and higher-elevation snow over parts of the Pacific Northwest and Northern California. Elsewhere, return flow off the Western Gulf of Mexico will produce light rain over parts of the Western Gulf Coast on Friday. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php