Snow Rollers

The winter of 2008-09 was a big one for snow in the Northwest and elsewhere. The mid-valley received 5 inches of snow in December, but areas north of us reported a lot more. At Portland Airport (PDX), the seasonal total of 23.6 inches was the third highest ever, topped only by 1949-50 (44.5”) and 1968-69 (34”). The 19 inch total reported in December made that month the snowiest December ever at PDX.

Farther north and east, Spokane set a record for most snow in a season. In one 36-hour period, 23.3 inches of snow fell. The seasonal total of 97.7 inches was Spokane’s highest ever. Oddly, 2007-08 had the third highest snowfall total ever (records go back to 1893).

The northern plains were also been hit hard. Fargo, North Dakota set a record for snowfall and precipitation for March. Bismarck, North Dakota set an all-time record for snowfall in December and had the second snowiest March, and total seasonal snow (100.2 inches) was the second highest ever. International Falls, Minnesota, with the reputation as the nation’s icebox, recorded 124.2 inches of snow this winter. That tops the old record of 116 inches set in 1995-1996.

Back to the Northwest, and a very unusual weather phenomenon: snow rollers.

According to Wikipedia, a “snow roller” is:

“a rare meteorological phenomenon in which large snowballs are formed naturally as chunks of snow are blown along the ground by wind, picking up material along the way, in much the same way that the large snowballs used in snowmen are made.”

Snow rollers are typically cylindrical in shape; they are generally hollow since the inner layers, which are the first layers to form, are weak and thin and often crumble,  leaving what looks like a doughnut.

The following conditions are needed for snow rollers to form:

  • The ground must be covered by a layer of ice.
  • The ice must be covered by wet, loose snow with a temperature near freezing (32 deg F)
  • The wind must be strong enough to move the snow rollers, but not strong enough to blow them too fast.
  • In some cases, gravity can move the snow rollers downhill, enabling them to grow as they move.

A few weeks ago, an amazing snow roller occurrence took place on the Camas Prairie in Idaho. My friend Jeanne’ sent me a Web link which I will share with you.

From the web link below, according to the Spokane office of the National Weather Service: “On the evening of March 31st, 2009, Tim Tevebaugh was driving home from work east of Craigmont in the southern Idaho Panhandle. Across the rolling hay fields, Tim saw a very unusual phenomenon. The snow rollers that he took pictures of are extremely rare because of the unique combination of snow, wind, temperature and moisture needed to create them. They form with light but sticky snow and strong (but not too strong) winds. These snow rollers formed during the day as they weren’t present in the morning on Tim’s drive to work.”

There are amazing pictures of cylinders of snow which remind me of the cylindrical hay bales we see in summer in the mid-valley. The link is here:

http://www.wrh.noaa.gov/otx/photo_gallery/snow_rollers.php

Here are a couple of pictures:

Based on estimations from Tim as well as the blades of grass in the picture, most of the snow rollers were about 18″ in height, while the largest rollers were about 2 feet high.

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About George Taylor

Climatologist, husband, father (3), grandfather (2)
This entry was posted in Weather, Weather Matters. Bookmark the permalink.

One Response to Snow Rollers

  1. Garron near washington square says:

    Thank you Professor Pierce,

    I have never heard of these before, and I find these pictures absolutely fascinating! Will we see these this winter rolling along I 84? Thanks for all the interesting weather tid bits you find along the way.

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