Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EST Sat Dec 14 2024 Valid 00Z Sun Dec 15 2024 - 00Z Tue Dec 17 2024 ...Heavy mountain snow forecast for the Sierra Nevada late Saturday, and then the Great Basin and northern Rockies into Sunday... ...Wintry mix including some ice continues for portions of the Upper Midwest late Saturday, spreading into the central Appalachians Sunday... A low pressure system centered over the Midwest states Saturday evening is forecast to track across the Ohio Valley tonight and then across the northern Mid-Atlantic and Northeast Sunday and into Sunday night, with generally light rain for most areas affected. Some mixed precipitation, including some light freezing rain, is also likely across portions of Wisconsin and Michigan, and also the Central and northern Appalachians, where some winter weather advisories are now in effect. More impactful winter weather is expected for the higher terrain of eastern West Virginia and into south-central PA, where winter storm warnings are in effect. The anomalously strong surface high over the Northeast U.S. will provide some cold air damming once this system arrives, with warmer air aloft over-riding the colder air closer to the surface providing the environment for mixed wintry precipitation. Once that system departs, another area of moderate to locally heavy rain is likely to develop Monday from the central Plains to the Ohio Valley in conjunction with a cold front intercepting moist southerly flow from the Gulf of Mexico. The occluded surface low well to the north near Lake Superior should have enough moisture to provide mainly light snow across portions of North Dakota and into northern Minnesota. Breezy to windy conditions are likely to develop in the wake of this front across the Upper Midwest and Great Lakes region into Monday night. Multiple rounds of precipitation are expected to continue from the northern half of California to Washington state as a couple of shortwaves pass through the region, with the first moving inland this evening, followed a second one Monday afternoon. Heavy snow is expected for the Sierra Nevada with the first event, with 1-2 feet of accumulation likely for the higher terrain. Moderate snow is then expected for the Intermountain West mountain ranges and then the Northern Rockies as the moisture associated with this moves inland. The next round likely arrives during the overnight hours Sunday night, with rain near the coast and moderate to heavy snow from the Cascades to the northern Sierra Nevada. Hamrick Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php