Lack of snow has led to larger frost depths


While many snow enthusiasts are already considering this winter a big fat bust, ice fishers, skaters, and wranglers are jumping for joy… and can do it “safely” on our frozen lakes.  The frost depth across the state (for the most part) is now some of the deepest it’s been at this point in the winter since 2014 and the reason has less to do about the cold, and more about the lack of snow.

What many may not realize is that snow is an insulator, much like a blanket would be.  If the snow is at least a couple inches deep, then it can insulate the ground from the bitter cold of the air above it and keep it relatively warm… at least warmer than it otherwise could be if the snow wasn’t there.  For this reason, the sooner we get snow in the fall, the longer it can take for the ground to freeze beyond the top inch or two.  This year though, with our lack of snow and our bitter cold temperatures since Christmas, our frost depth, the depth at which the ground is frozen, is over 2 feet deep in some places… and still growing.

The map above shows some “official” frost depth locations with many of them coming in with at least a 20” depth.  Even in the metro, which has been free of deep snow pack all winter, has a couple locations with 26” of frost.  That’s impressive for metro standards because of our heat island effect.  Notice locations that have had deeper snow pack this winter have less frost like Waseca and Menomonie, Wisconsin.

While the time of year that the frost depth reaches its peak is highly dependent on temperatures and snow cover, it usually occurs sometime in February or early March, which means we could have a solid 6 more weeks where the ground frost is continuing to expand.  This could set the stage for a 3 or even 4-foot frost depth in spots which would be great for ice enthusiasts, but could have BIG flood implications in the spring if heavy rain or snow moves in.

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