An Alberta clipper will move across the Northern Plains late tonight and Thursday. Rain will spread into southeast South Dakota around midnight, with precipitation expanding over much of the area after midnight. As the air cools after midnight, there may be a brief period of sleet or freezing rain before changing to all snow. By early Thursday morning, precipitation is expected to be all snow over most of southeast South Dakota, southwest Minnesota, and with a mix of rain and snow in northwest Iowa. Precipitation is expected to change to all snow in northwest Iowa during the morning rush hour.
This system is unstable and strengthening, which could result in a period of intense snowfall rates over portions of southeast South Dakota and northwest Iowa on Thursday morning. This will result in a narrow corridor of 5 to 8 inches of snowfall, bordered to the north and south by a fairly sharp gradient in snowfall accumulations, as seen in the above map of forecast snow totals. Because the band of snow is expected to be so narrow, a small shift in the location in the band could result in increased snow amounts.
The latest information on this quickly evolving Winter Storm can be found on our Winter Weather Briefing Page.