Water vapor satellite image - National Environmental Satellite Data and Information Service (NESDIS)
National Weather Service Duluth, MN radar loop of standing wave induced snow
8:13 PM to 9:12 PM CST January 25, 2010
* Click HERE for an informal case study that analyzes the standing wave with greater detail.
A prolonged snow event began on Saturday the 23rd as freezing rain which changed to sleet and then mostly snow depending upon elevation. Most of the heaviest snow fell from daybreak Sunday morning into early afternoon. Temperatures around freezing resulted in a very dense wet accumulation. Periods of lighter snow continued from the rest of the day into Monday then finally ended around midnight Tuesday the 26th.
National Weather Service snowfall reports showed a very wide range of accumulations due to temperatures being a few degrees warmer near the lake. Only 2 to 6 inches accumulated near the immediate lakeshore while 12 or more inches accumulated along and inland of the ridge crest. Localized amounts of 12 or more inches also fell south of Superior, WI. Officially 13.7 inches fell at the National Weather Service office in Duluth.
A rare event added 1 to 2 inches of additional accumulation at the end of the storm Monday evening. An apparent standing atmospheric wave induced by the north shore ridge of Lake Superior produced a period of moderate to heavy snow. Standing wave (or gravity wave) events are not unusual but rarely does the snow reach the ground in Duluth at least in this observers experience since moving to Duluth in 2001. When it does, the snow is very light on the northwest fringe of the event. Usually, the snow falls downstream to the southeast over the lake and adjacent sections of northwest Wisconsin.
For more information on atmospheric waves, see the "Mountain Waves / Standing Waves" discussion on the Duluth Local Influences page.