Winter Storms Roll In

The year's first major nationwide winter storm is likely to begin crawling across the US today, according to weather forecasters. The system is expected to bring significant snowfall to the Great Plains and Upper Midwest, along with multiple inches of rain and possible tornadoes in the South throughout the week.

The culprit is a phenomenon known as an atmospheric river (see 101)—narrow bands transporting water vapor from the Pacific tropics to the US. The precipitation arrived along the West Coast over the weekend, dropping up to two feet of snow in the Sierra Nevada, with another two feet possible as the storm fully moves through. The system is expected to meet cold air as it moves through the Great Plains and into the Great Lakes region, and is likely to reach the Northeast by week's end.

Outside mountain regions, parts of North and South Dakota are expected to see the most snow, with up to 2 feet projected around the city of Bismarck, North Dakota, by Wednesday.