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. Snow amounts of 10 to 18 inches fell in Duluth and surrounding communities in Minnesota over a 48 hour period. The event began around 7:30 PM Friday March 2nd and ended around 9 PM Sunday March 4th. 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 2nd, much of the precipitation fell as snow pellets but transitioned to mainly snow late evening into 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 (DAK) measured a snow increase of 2 inches an hour from 2 AM to 3 AM Saturday morning. Yes, I was up most of the night!

From 8 AM March 3rd dendritic ice crystals began to appear. The snow became increasingly dendritic through the morning causing the snow pack 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 at DAK and 11.4 inches at NWS DLH.

Storm images compliments of the National Centers for Environmental Information

10:05 PM CST (0405 UTC) March 2nd, 2012

11:42 PM CST (0542 UTC) March 2nd, 2012

1:49 AM CST (0749 UTC) March 3rd, 2012