Current Advisory

GNFAC Avalanche Advisory for Fri Mar 6, 2015

Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, March 6, at 7:30 a.m. Grizzly Outfitters in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.


Mountain Weather: 

This morning temperatures were almost 10 degrees warmer than yesterday morning. Temperatures in most places were near 20 degrees F and ridgetop winds were blowing 20-30 mph from the NW in some locations and SW in others. Winds and temperatures were a little calmer and cooler near West Yellowstone and Cooke City. Today will be similar to yesterday but warmer. Temperatures will be in the 30s and 40s F, and winds should blow 20-30 mph at ridgetops mostly from the W and NW.


Snowpack and Avalanche Discussion: 

Bridger Range   Madison Range   Gallatin Range   

Lionhead Area near West Yellowstone   Cooke City

Today’s avalanche problem is wind slabs up to a foot thick resting on small, weak facets.

  • One was triggered in Wyoming Bowl near Big Sky on Wednesday (photo1, photo2).This one was notable for how wide it broke, about 200 yards across.
  • Another was triggered yesterday in Hyalite Canyon in the northern Gallatin Range (photo). This one was smaller but was triggered by a really small piece of cornice.
  • A skier triggered a few small ones north of Big Sky on Wednesday as well that ran 100-300 vertical feet.
  • Yesterday the Bridger Bowl Ski Patrol triggered fresh wind slabs 10-15 inches thick near the ridge by dropping small cornices or ski cutting.

What makes many of these wind slabs a greater problem is they rest on weak faceted crystals that formed during the last week (video). Doug found this layer near West Yellowstone, but did not find it near Bridger Bowl. Skiers near Cooke City found this layer of facets capped by touchy wind slabs yesterday. This weak, faceted layer will make wind slabs easier to trigger, break over larger areas, run further downhill, and remain unstable longer than normal. Warm, dry weather will help this problem go away but it should remain an issue through the weekend.

This combination of a wind slab on top of small facets isn’t widespread, but can be found on most aspects near ridges or features collecting wind-blown snow. Triggering an avalanche probably won’t bury a person; the danger is being pushed into trees or rocks. Today heightened avalanche conditions exist where you can find this slab/facet combo, and the avalanche danger is rated MODERATE on wind loaded slopes steeper than 35 degrees. All other slopes have a LOW danger.


The Snow Science Program at MSU needs your Help!

They are looking for backcountry skiers and sledders to help them with a study on Human Factors. Watch this 2:46 minute video for details.

Forum on Snow Science and the Human Factor on video.

In case you missed it, here's the entire 1:13 hour video from the forum on Snow Science and the Human Factor at MSU. John Stifter, editor of Powder Magazine, talks about his own personal experience with the avalanche that killed three of his friends in 2012 at Tunnel Creek. Doug Chabot gives a presentation about Sidecountry Skiing and Digging Pits starting 44 minutes into the program.


I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.


AVALANCHE EDUCATION and EVENTS

Take a look at our Education Calendar for all classes being offered.

1-hour Avalanche Awareness, Bozeman, REI, 6:30 - 8 p.m., Wednesday, March 11.


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