We triggered a small soft slab avalanche when skinning near the top of Pair Of Chutes in the Playground. The slab was about 1 foot thick, fist hardness, propagated 20 feet wide and ran 50 feet before breaking up and arresting. The slab did not entrain additional snow as it slid. The avalanche hit my feet but did not disturb my balance. However, it could have been dangerous above consequential terrain. Moderate gusting to high winds were sustained the entire day and wind slabs were widespread in the backcountry terrain north of Bridger.
On January 26 we saw a handful (4-6?) of old wind slab avalanches of various ages. The most recent and largest appearing, but still not very fresh, was on the north side of Scotch Bonnet (attached photo). Most were D1-D1.5, the slide pictured was D1.5-2. Photo: GNFAC
We saw most terrain in the motorized area north of Cooke City. We went passed Round Lake to Goose Lake wilderness boundary, around the north of Sheep Mtn. and Scotch Bonnet to Lulu Pass, out to Mt. Abundance, back south over Daisy Pass, and around town hill/Miller Rd., then up and down Sheep Creek to the top.
Skies were clear and wind was calm to non-existent with cold temperatures (singles to teens F).
We saw a handful (4-6?) of old wind slab avalanches of various ages. The most recent and largest appearing, but still not very fresh, was on the north side of Scotch Bonnet (attached photo). Most were D1-D1.5, the slide pictured was D2.
We dug on the southeast shoulder of Mt. Abundance (profile attached). Snow depth was 3.5-4 feet and we had ECTNs. There were some soft-ish facets near the bottom of the snowpack. We also dug a pit in Sheep Creek and had an ECTX, snow depth of 4-5 feet. We did a lot of hand pits to look for recently buried facets. Small sugary facets were generally easy to find, buried 3-6" deep below soft snow. If and where snow is drifted into thicker slabs, these facets might make those slabs more reactive.
A lack of recent avalanches combined with minimal recent loading from new snow and wind point to avalanches being unlikely. The recent large persistent slab in Hayden Creek shows that although slides are unlikely they could be big. We would rule-out big slopes that are heavily wind-loaded, and otherwise feel ok in steep terrain while sticking to safe travel protocols (carry a transceiver, probe AND shovel, and only expose one person at a time to avalanche terrain).
We skied north from Texas Meadows to the Playground. Strong southerly winds were actively building wind slabs up to 25 cm deep in immediate lees at treeline. We experienced a few instances of cracking in this wind slab, propagating 2 or 3 meters from our ski tips.
<p><span><span><span><span><span><span>Snowfall on Friday favored the mountains near Bozeman and Big Sky with up to 8” of low density snow, and last Wednesday the Bridger Range had 16-20” of very low density snow (0.2-0.3” SWE). Even the lightest winds were able to transport this snow into thin soft slabs, and today’s stiff wind in the Bridger Range will form thicker fresh drifts that will be easy to trigger. Be alert for these </span></span></span></span></span></span><span><span><span><strong><span><span>wind slabs</span></span></strong></span></span></span><span><span><span><span><span><span> across many elevations and mid-slope, not just near the prominent ridgelines.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Avalanches breaking deeper are unlikely. If you’re happy with the stability of the most recent snow, dig down a couple feet to make sure older wind slabs are also well-bonded. The avalanche danger is MODERATE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Near Cooke City and West Yellowstone a person can trigger avalanches that break many feet deep on weak snow near the bottom of the snowpack. A recent very large </span></span></span></span></span></span><span><span><span><strong><span><span>persistent slab avalanche</span></span></strong></span></span></span><span><span><span><span><span><span> broke south of Cooke City within the last 2-3 days, and shows these remain possible (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33847"><span><span><span><strong><span…;). Although these huge slides have become difficult to trigger, they have unsurvivable consequences and require careful terrain selection. Additionally, wind slab avalanches 1-2 feet deep can be triggered where recent snow was drifted into stiffer or thicker slabs. Avoid big wind-loaded slopes with variable snow depth that might have thin spots as potential trigger points for deep avalanches. Choose smaller slopes with clean runouts generally free of trees, rocks or cliffs. The avalanche danger is MODERATE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Near Island Park there has been less snow over the last couple weeks, allowing the snowpack to become more stable, and avalanches are unlikely. Unlikely does not mean impossible, so if you travel on slopes steeper than 30 degrees keep in mind weak layers that are buried near the bottom of the snowpack and below thin slabs of recently drifted snow. You can hedge your bets of not triggering deeper persistent slab avalanches by choosing slopes with minimal previous wind-loading and a generally uniform snow depth. Stay alert for fresh soft slabs that may be large enough to be harmful in isolated areas, and remember even a small slide can easily push you off a cliff or into trees. Carry rescue gear and expose only one person at a time to avalanche terrain. Human-triggered avalanches are unlikely and the avalanche danger is LOW.</span></span></span></span></span></span></p>
Do you like to hike? Do you like to ski/ride? Then the King & Queen of the Ridge on 2/1 is for you. Hike, ride and raise money for the Friends of the Avalanche Center at Bridger Bowl this year! Join this fun event to promote and support avalanche safety and awareness! Fundraising prizes for the top 5 individuals who raise over $500.
While touring today, we saw a deep slab avalanche at the southern end of the Hayden Creek drainage. NE aspect. It seemed to be recent, likely in the last day or so.
While touring today, we saw a deep slab avalanche at the southern end of the Hayden Creek drainage. NE aspect. It seemed to be recent, likely in the last day or so. Photo: N Mattes
