GNFAC Avalanche Forecast for Wed Jan 15, 2025
<p>Stability is improving slowly in the Southern Madison and Southern Gallatin Ranges and the mountains around West Yellowstone. Persistent weak layers buried 1-3 feet deep make human-triggered <strong>persistent slab avalanches </strong>likely on steep slopes.</p>
<p>The snowpack continues to demonstrate its instability. On Monday (exact timing unknown), a skier triggered an avalanche across the river from Bacon Rind that appeared to fail on the problematic weak layers (<a href="https://www.mtavalanche.com/node/33562"><strong><span>details and photos</span></strong></a>). At Bacon Rind, we triggered countless collapses that shook the snow off nearby trees (<a href="https://www.mtavalanche.com/node/33534"><strong><span>observation and video</span></strong></a>), and at Lionhead, we triggered several large collapses and noted the weak snowpack structure (<a href="https://www.mtavalanche.com/node/33529"><strong><span>observation/</spa…; </strong><a href="https://www.youtube.com/watch?v=I6nDBNZli-Y"><strong><span>video</span>…;
<p>Avalanches breaking within recent drifts of wind-loaded snow as <strong>wind slabs </strong>is a secondary concern that exacerbates the persistent slab problem by adding weight to slopes and potentially triggering a deeper slide (<a href="https://www.mtavalanche.com/node/33511"><strong><span>slide near Two Top</span></strong></a>).</p>
<p>Enjoy great powder turns and ride in low-angle terrain, avoiding slopes steeper than 30 degrees. The danger is CONSIDERABLE.</p>
<p>In Cooke City and Island Park, triggering a <strong>persistent slab avalanche </strong><span>that breaks 4-6 feet deep is possible.</span></p>
<p>Within the last week in Cooke City, large avalanches occurred naturally and with remote triggers from distant flat terrain (<a href="https://www.mtavalanche.com/node/33461"><strong><span>Ian and Alex’s video</span></strong></a>). The most recent slides occurred on Sunday and Monday (<a href="https://www.mtavalanche.com/node/33520"><strong><span>photos and details, Photos/ details 2</span></strong></a>). Similar concerns exist in Island Park, but with less recent snowfall, we have seen less activity (<a href="https://www.mtavalanche.com/node/33433"><strong><span>video</span></str…;). Avoid steep, wind-loaded terrain where recent drifts are present. These are the most likely locations to trigger large <strong>persistent </strong>and <strong>wind slab avalanches</strong>.</p>
<p>Lean on careful terrain evaluation to <em>reduce the chances of triggering a slide</em> and the <em>consequences if one occurs</em>. Steeper terrain, wind-loaded slopes and terrain with variation in depth are more likely to avalanche. Larger slopes with terrain traps enhance the consequences of getting caught. To minimize uncertainty, ski and ride in terrain less than 30 degrees.</p>
<p>The avalanche danger is MODERATE.</p>
<p><span><span><span>In the mountains around Bozeman and Big Sky, <strong>wind slab avalanches </strong>are the primary concern. For the third day, winds gusting above 40 mph are hitting the Bridger Range. The distribution of potential instability related to wind loading is widespread. Lighter winds in the Northern Gallatin and Northern Madison Ranges will drift snow in more predictable patterns near ridgelines and upper-elevation gullies. Evaluate terrain and surface snow for instability, watching for shooting cracks and feeling for a stiffening snow surface. <em>Seek out </em>terrain sheltered from the wind, where you will find safer conditions and better snow.</span></span></span></p>
<p><span><span><span>Triggering a <strong>persistent slab avalanche </strong>on buried weak layers is unlikely (Portal Creek <a href="https://www.mtavalanche.com/node/33557"><strong><span>observation and video</span></strong></a>). Areas where it remains possible include shallower spots on steep, rocky slopes, near rock outcroppings, or wind-scoured ridges (<a href="https://www.youtube.com/watch?v=xHr_3Bdtq1o"><span>Blackmore Video</span></a>). </span></span></span></p>
<p><span><span><span>The avalanche danger is MODERATE. </span></span></span></p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Avalanche Fundamentals with Field Session for non-motorized travelers during the last weekend of January.
On Tuesday, January 19, 2016, a Yellowstone Club (YC) Ski Patroller triggered an avalanche on a wind-loaded slope which released on his second turn. The slide broke 2-4 feet deep, 300 feet wide and carried him through a terrain trap of thick trees. He was partially buried 300 vertical feet below in the toe of the debris. His partners reached him within three minutes, but the trauma was fatal.
Forecast link: GNFAC Avalanche Forecast for Wed Jan 15, 2025
Human triggered avalanche near Bacon Rind
While driving to and from West Yellowstone today, I noticed what is potentially a skier/snowboarder-triggered avalanche on the east side of HWY 191 on a West/Southwesterly aspect, directly across the highway from the Bacon Rind Area and Snowslide Creek. There were numerous tracks through steep rocky chutes next to the road, one of which had avalanched perhaps 75' wide, 18-24" deep, and running nearly to the flats at the base of the slope. Judging by the thin layer of fresh snow it potentially happened on Sunday or maybe Monday. There were tracks through the cliffs above the slide and coming out of the slide.
***Attached video is from a GNFAC field work at Bacon Rind unrelated to the avalanche, but likely on the same day***
USFS Snow rangers commuting to and from West Yellowstone noticed a human-triggered avalanche across the Gallatin River from Bacon Rind. Photo: K. Marvinney
USFS Snow rangers commuting to and from West Yellowstone noticed a human-triggered avalanche across the Gallatin River from Bacon Rind. Photo: K. Marvinney
Forecast link: GNFAC Avalanche Forecast for Wed Jan 15, 2025
Deep and Stabilizing in Portal Creek
We rode into Portal Creek to the ridgeline above Hidden Lakes and back below Windy Pass. During our ride, we noted no avalanche activity or signs of instability. We dug twice to the ground. Once above Hidden Lakes and once in the corner of an avalanche path below Windy Pass.
Bottom Line:
- The snowpack is DEEP. The measured HS was "1 Dave" or 6'5" (200 cm).
- Stability is looking good in our pits, and we are optimistic.
- ECTNs-mid teens within the layers of the post-Christmas storm snow.
- Faceted snow near the base of the snowpack is hardening and rounding. Even with extra prodding (deep taps and an unofficial cross-slope PST), we couldn't get it to break or propagate failure.
- The mountain range is expansive, and one must assume spatial variability on both slope and certainly the range scale, but this is good.
Big Picture:
- Other than one avalanche that appeared to break on persistent weak layers below Maid of the Mist, Ian and I couldn't think of another persistent slab avalanche in the Northern Gallatin Range.
- Wind Slab avalanches are the most likely issue.
- Danger is dropping quickly.
- We don't trust facets often and aren't ready to write off the basal weakness, but triggering an avalanche on these layers seems unlikely for now.
- This puts wind slab avalanches as the primary concern... and it hasn't been very windy. So, this seems limited for now.
Terrain Recommendations:
- It is appropriate to consider riding and skiing in avalanche terrain if one is willing to accept the inherent levels of uncertainty involved with steep, backcountry terrain.
- We are pessimistic by nature and like to hedge our bets. The way to do this is by selecting terrain less likely to avalanche (not as steep, more uniform in depth—less rocky, potentially shallow areas, and not wind-loaded) and terrain with lesser consequences (smaller slopes, fewer terrain traps, clean runouts).