Missoula Avalanche Center: New Snow & Poor Snowpack Structure | No Danger Rating In MT Backcountry

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Weak layer of snow on December 16th. Image: Missoula Avalanche Center

Missoula Avalanche Center: No Danger Rating

By: Travis Craft

Good morning, this is Travis Craft with the West Central Montana Avalanche Center’s weather and avalanche update for December 17, 2017. This danger rating does not apply to operating ski areas, expires at midnight tonight and is the sole responsibility of the U.S. Forest Service.

Weather and Snowpack

Mountain temperatures range from 8 F to 18 F in the region. Winds are 8 mph with gusts of 11 mph out of the SSW in the Bitterroot. Point Six, in the northern part of the advisory area, winds are 22 mph with gusts of 29 mph out of the WNW.  The advisory area received 0 to 1 inches of snow in the last 24 hours.

Wind Slabs. Image: Missoula Avalanche Center

The primary avalanche problem is wind slabs. Leeward terrain has wind slabs. Look for rounded pillows of snow near ridgelines and recognize signs of instability such as cracking in the surface snow.  Look for cross-loaded terrain as well as ridge tops.

Persistent slabs. Image: Missoula Avalanche Center

The secondary avalanche problem is persistent slabs.  The new snow will be stressing and burying layers of concern.  The two layers of concern are the buried surface hoar and the near surface facets on top of the Thanksgiving crust.  Dig a pit to assess how reactive these layers are before committing to any slope over 30 degrees.

Avalanche and Weather Outlook

A system is going to move into tonight with new snow and 50 mph ridge top winds.  Look for the avalanche danger to rise when this storm moves in with the addition of new snow and strong winds.

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