A rare treat from nature: Perfect snow doughnuts
http://seattletimes.nwsource.com/html/localnews/2003622603_donut17m.html?syndication=rss

MIKE STANFORD
Snow doughnuts, like these found in the North Cascades, form when snow
conditions are just right.
A rare treat from nature: Perfect snow doughnuts
By Susan Gilmore
Seattle Times staff reporter

No, it's not a promotion for Winchell's or Krispy Kreme.
"This is no joke. We did not build it," said Mike Stanford, an
avalanche-control expert with the state Department of Transportation
(WSDOT). "They are a natural occurrence in nature."
Stanford found frozen doughnuts of snow on the top of Washington Pass in
the North Cascades this week when he was doing avalanche-control work.

At first he couldn't believe his eyes: Perfectly shaped doughnuts had
rolled down the mountainside and frozen in place.
He said it's only the second time in his 30 years of working in the snow
that he's seen anything like it.
The larger of the snow rollers, as they are commonly called, was about
24 inches tall, he said, large enough for him to put his head through
the hole.

Stanford said snow rollers form when there is a hard layer on the snow,
covered by several more inches of dense snow. "Then you add a steep
slope and a trigger such as a clump of snow falling out of a tree or off
of a rock face."
As gravity pulls a clump down, it usually rolls down the hill and
collapses, creating what the WSDOT calls a pinwheel. Or it will not roll
at all, and come down in an avalanche of snow. But if the snow is the
perfect density and temperature, it rolls down leaving a hole in the
center, Stanford said.

Strong, gusty winds also can be a factor, according to NOAA's National
Weather Service office in central Illinois, where snow rollers have
occurred.
As soon as the sun comes out and it warms up, the doughnuts would be
gone, Stanford said Friday.

Don't think you can drive up to see them. They sit on Washington Pass,
14 miles east of where the highway is closed for the winter.
"No, there are not many of them," Stanford said of his discovery. "The
temperature and snow conditions have to be just right."

Susan Gilmore: 206-464-2054 or sgilmore@seattletimes.com