MARBLEMOUNT, Wash. - WSDOT maintenance crews spotted a rare snow doughnut this week while doing some reconnaissance work on the North Cascades Highway.

WSDOT

At least, these doughnuts are fat-free!

Crews were scouting the avalanche chutes above the pass and measuring the snow depth over the highway when they saw it.

According to Mike Stanford of WSDOT, everything has to be just right for snow doughnuts - also called snow rollers by some - to happen. The snow needs to have certain elasticity, and air and ground temperature have to be at just the right level.

He says it starts with a rolling snowball on a steep slope, which curls, and instead of collapsing on itself it just continues to roll. He says it is a freak occurrence in nature, but that it does happen once in a while, and when it does happen, it's not unusual to see more than one.

The WSDOT crew says they plan to start plowing snow off the pass March 26 and expect the work to take up to six weeks to complete.

The snow is deeper than previous years. They hope to have the pass open to drivers by mid-May.