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Lake Effect/Lake Vortex Enhanced Snow

Duluth, MN

March 2 to 4, 2012

A weak but persistent upper trough and associated surface trough, combined with conditions favorable for lake effect snow to produce a long duration snowfall. The 48+ hour event began around 7:30 PM Friday, March 2, and ended around 9 PM Sunday, March 4. Lake vortices (or lake swirls), three, possibly four, appeared to help focus snowfall at the head of Lake Superior and adjacent terrain, especially in Minnesota. Early in the event the evening of March 2, much of the precipitation fell as snow pellets but transitioned to mainly snow from late evening into the overnight. Localized bursts of heavy snow produced snowfall rates of 1 to 2 inches an hour even when the dominant precipitation type was snow pellets. This observer measured a snow increase of 2 inches from 2 AM to 3 AM on Saturday morning. Yes, I was up most of the night!

From 8 AM March 3 dendritic ice crystals began to appear. The snow became increasingly dendritic through the morning causing the snowpack to become very fluffy. Of interest in this event is that snow coverage and intensity seemed to pulsate. The radar would show a flare-up for several hours then the snow rapidly diminished to in some cases almost flurries. Then just as the event appeared to be about over the snow would blow right back up again!

Snow accumulated 14.8 inches as a personal measurement and 11.4 inches at the National Weather Service Office in Duluth.


Radar images from the National Weather Service in Duluth, MN

10:05 PM CST (4:05 UTC) March 2, 2012


11:42 PM CST (5:42 UTC) March 2, 2012


1:49 AM CST (7:49 UTC) March 3, 2012