PHotos attached of some natural avalanches near Cooke City today.
Avy1: NW aspect, around 10,000'. (This starting zone also avalanched in a similar way around Feb. 21).
Avy2: E aspect, around 9,000'.
Heavy snow and strong winds are creating dangerous avalanche conditions. The snow is letting up and the sun will poke out this weekend, but the snowpack needs time to stabilize. If the wind continues, loading from drifting is equivalent to loading from new snow. We observed shooting cracks where snow on top of a rain crust 6-12" deep was sliding easily on steep rolls.
Steer clear of steep slopes, especially those loaded by wind drifts and avoid gullies with walls over 30 degrees. Opt instead for meadows and tree riding under 30 degrees where the snow is deep, and you'll be safe from avalanches.
<p><span><span><span><span><span><span>Avalanches are likely within the newly wind drifted snow and also possible on deeply buried weak layers. 5-7” of dense new snow has drifted into much thicker cohesive slabs that will be easily triggered today and will break plenty deep to bury you. Hurricane force winds will have built drifts in unusual places. With such strong winds it may be hard to identify which slopes are loaded and which are just wind affected. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Simply avoid steep slopes altogether to avoid the possibility of triggering a huge, unsurvivable slide breaking deep in the snowpack. With incremental loading last week avalanches were triggered on weak layers buried in early January (</span></span></span></span></span></span><a href="https://youtu.be/nZFM_QZxG3Q"><span><span><span><strong><span><u><span>… City video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). I’m very worried about people triggering similar slides today. Don’t try to outsmart the snowpack or thread the needle near questionable terrain. Give the persistent weak layers time to adjust to this load by sticking to slopes less than 30 degrees and staying way out from under them as well. Large, human triggered avalanches are likely and the avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>
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<p><span><span><span><span><span><span>Less snow fell around Bozeman, but very strong winds still blew that new snow into drifts sitting on top of persistent weak layers. Last week, large, deep avalanches were triggered after a very moderate loading event (</span></span></span></span></span></span><a href="https://youtu.be/42Zk3eLEMvE"><span><span><span><strong><span><u><span>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Similar slides are possible today and with a bit of loading are somewhat more likely today than they were yesterday. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>If the potential for deep slab avalanches isn’t keeping you out of avalanche terrain entirely today, be on the lookout for wind drifts and dig to test for recently buried weak layers in the upper snowpack. Expect wind drifts in unusual places at low elevations and far below ridgelines. Cracks shooting out in front of your skis or sled are clear signs that you’ve found an unstable drift that would avalanche on a steep slope.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Avalanche danger is MODERATE.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs). </span></span></span></span></span></span><span><span><span><span><span><span> </span></span></span></span></span></span><span><span><span><span><span><span> </span></span></span></span></span></span></p>
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<p><span><span><span><span><span><span>Heavy snowfall and strong winds yesterday makes for dangerous avalanche conditions today. There are ~18” of storm snow that could avalanche by itself (deeper in drifts) and slides could also break deeper in the snowpack. Decision making is simple today - simply avoid steep slopes and give them a wide berth if you’re traveling beneath them. See </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=SL1_7YZjWKI&list=PLXu5151nmAvTi1DBS…’s video update</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> from yesterday for more travel advice. </span></span></span></span></span></span></p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
105 mph gusts yesterday afternoon at Lone Mountain and Lionhead
My group and I spent March 5th - 8th in the Hellroaring Creek drainage on the SW side of the Centennials. We were right on the heels of the 13ish day long storm in the Island Park area. From what we gathered, the snowpack was handling the loading very well. We saw no natural avalanches. Pits dug on shady aspects were around 250cms deep and had few noticeable weak layers and no reactivity during testing. Pits on South and West aspects were about 200cms deep and had a thin pencil hardness crust (melt/freeze I believe) ranging from 115-140cms above ground. This crust had facets around it and was reactive in column tests but showed now propagation in the ECTs.
Snowpit from a SE aspect around 9100', from today near Cooke City.
HS 228cms. ECTN's in upper layers on density changes.
About 85cms of settled snow from the storm cycle that started on Feb. 19th.
No new avalanche activity to report.
No collapsing.
We skied the ridge north of Blackmore (Tomahawk Ridge?) traveling between 6800' -9200' on SE-NE aspects.
On the ridge above, ~9400' on a NE aspect there was a natural avalanche, maybe cornice failure, probably same timeframe as the Divide slides. ran ~600'.
HS-N-D2-R2-O
Photo: R. Griffiths
