Skiers in the Hellroaring Creek area of the Centennials got a good view of the aftermath of an avalanche warning on March 14 and 15. They saw many avalanches that broke 3-5 feet deep. Photo: A. Dunn
Skiers in the Hellroaring Creek area of the Centennials got a good view of the aftermath of an avalanche warning on March 14 and 15. They saw many avalanches that broke 3-5 feet deep. Photo: A. Dunn
Skiers in the Hellroaring Creek area of the Centennials got a good view of the aftermath of an avalanche warning on March 14 and 15. They saw many avalanches that broke 3-5 feet deep. Photo: A. Dunn
Toured into the hellroaring creek 3/15-3/19. Snowing and blowing hard on 3/15 till approx 1500 hrs when wind veered to the north and skies cleared for the rest of the trip with generally cold temps and light winds. Solar aspects heating up in the day with extensive sun crusting on steeper slopes facing the south half of the compass. Observed aftermath of extensive avy cycle(s) one of which prior party reported occurred approx 3/10-11 at higher elevations on Nemesis (above 8000 ft.). And another on lower elevation steep slopes above creek at approx 7500 ft that may have ran during the storm on 3/14 as less snow covered that debris than the higher elev runouts. Everything observed were on westerly aspects and deep slab avalanches breaking approx 90-120 cm down. We did not investigate the weak layer. Suspect it to be the crust facet combo observed by a previous party in early March. Heavy wet snow possibly mixed with rain on 3/14-15 likely tipped the scales for these lower elevation slopes below 7500. No signs of instability of the new storm/wind slab during the five day trip, however we did get a few large collapses but these were isolated to heavily wind loaded areas in more exposed terrain. No other natural or human triggered avalanches observed during the trip. Many machiners were out testing steep slopes after the storm and we saw no signs of any human triggered avalanches. We did not measure height of snow but judging by the buried hut and the non-motorized boundary signs barely poking out of the snow, thinking about 10 feet deep at 8000 ft.
<p>Human-triggered avalanches are likely in the mountains around Cooke City and West Yellowstone where 4-7” of new snow fell, and moderate winds are drifting snow at Lionhead Ridge.</p>
<p>The primary concern is large avalanches breaking on persistent weak layers deep within the snowpack. Like a recent snowmobiler-triggered avalanche north of Cooke City, these could break 2-6+ feet deep and fail widely across slopes (<a href="https://www.mtavalanche.com/node/28695"><strong><span>details and photos</span></strong></a>). In the last month, we have been lucky that a large avalanche has not injured or killed a skier or rider in the many close calls and large avalanche cycles (<a href="https://www.mtavalanche.com/avalanche-incidents"><strong><span>Avalanche Incidents</span></strong></a>, <a href="https://www.mtavalanche.com/node/28681"><strong><span>Lionhead avalanche cycle</span></strong></a>). We have used up our nine lives, and getting caught and carried in an avalanche of this magnitude could easily be unsurvivable. Choose smaller, lower-angle runs sheltered from the wind. Avoid steep wind-loaded slopes and complex terrain with traps like rocks, cliffs, and gullies. Be cautious about crossing underneath steep slopes. If there are any questions, avoid all terrain steeper than 30 degrees.</p>
<p>Our secondary concern is smaller avalanches breaking within the new and wind-drifted snow. While smaller, these can be big enough to bury or injure a skier or rider on slopes where terrain features worsen the consequences of getting caught.</p>
<p>The danger is CONSIDERABLE.</p>
<p>The mountains around Bozeman and Big Sky received 2-4” of new snow. The primary concern is large avalanches breaking deep within the snowpack on persistent weak layers. Alex and I rode in the Taylor Fork area on Sunday, where we saw several deep slab avalanches that failed last week (<a href="https://www.youtube.com/watch?v=KJ0l4TlIh_I&list=PLXu5151nmAvTi1DBS…;, <a href="https://www.mtavalanche.com/node/28725"><strong><span>observation and photos</span></strong></a>). Deep slab avalanches have also occurred in the northern ranges of the advisory area, albeit with lesser frequency (<a href="https://www.mtavalanche.com/node/28455"><strong><span>Hyalite Peak slide</span></strong></a>, <a href="https://www.mtavalanche.com/node/28642"><strong><span>Northern Bridgers slide</span></strong></a>). Manage this problem with conservative terrain choices. Pick smaller slopes with less exposure to the wind and without complicating factors like cliffs and rocks or stay in terrain less than 30 degrees.</p>
<p>Yesterday in Frazier Basin, we found a weak snowpack structure in one of our pits and observed five loose snow avalanches on a steep face. These slides were only an inch or two deep, but they ran a long way and highlighted that the new snow might bond poorly to a melt-freeze crust that formed on many slopes (<a href="https://www.youtube.com/watch?v=a1aOgLTtZio"><strong><span>video</span>…;, <a href="https://www.mtavalanche.com/node/28735"><strong><span>observations</spa…;). Watch for signs of instability like shooting cracks and recent avalanche activity within the new snow if you plan to enter avalanche terrain.</p>
<p>Heightened avalanche conditions exist, and danger is MODERATE.</p>
<p>Please share avalanche, snowpack or weather observations via our<a href="https://www.mtavalanche.com/node/add/snow_obs"><span> </span></a><a href="https://www.mtavalanche.com/node/add/snow_obs"><strong><span>website</s…;, email (<strong>mtavalanche@gmail.com</strong>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
<p>Human-triggered avalanches are likely in the mountains of Island Park, where 5-7” of new snow fell, and moderate winds are drifting snow. Avalanches within the new and wind-drifted snow will be large enough to carry and bury a rider or skier. Larger slides are possible on heavily wind-loaded slopes or where there are underlying weak layers. Choose smaller, lower-angle slopes that are sheltered from the wind and avoid steep wind-loaded terrain and complex slopes.</p>
<p>See <a href="https://www.youtube.com/watch?v=O-lUMunzE1k"><span>Doug’s video</span></a> for a rundown on the aftermath of last week’s avalanche warning. Snow bikers in the bowl of Mount Jefferson saw further evidence of a large avalanche cycle noting a 6’+ deep crown on a heavily wind-loaded slope (<a href="https://www.mtavalanche.com/images/23/deep-avalanche-mt-jefferson"><str…;).</p>
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Snow bikers saw the debris and crown of a large avalanche that broke on a heavily wind-loaded slope on Mt Jefferson in the Centennial Mountains. Look to the upper left of the photo to see what they estimated as a 6' deep crown. Photo: R. Gravatt
From obs 3/20/23: "Yesterday we toured up into Emigrant gulch. At around 2pm we observed a small point release on the East face of Emigrant, either a small cornice break or wet loose, that ran for about 200ft before stepping down to a deep slab that appeared to be about 3ft deep and 100ft across."
From obs 3/20/23: "Yesterday (3/19) we toured up into Emigrant gulch. At around 2pm we observed a small point release on the East face of Emigrant, either a small cornice break or wet loose, that ran for about 200ft before stepping down to a deep slab that appeared to be about 3ft deep and 100ft across." Photo: Schreier
