Just wanted to send in a quick ob about snowfall.. in the last 24 hours at the Roost it snowed about 4 inches despite Fisher recording 0 inches of SWE
<p>Dangerous avalanche conditions exist across the forecast area. Avalanches are likely to fail on persistent weak layers buried 2-4 feet deep (<strong>persistent slabs</strong>) and, around Bozeman and Big Sky, with higher 24-hour snowfall totals, slides will also release within the new snow up to 2 feet deep (<strong>storm slabs</strong>). Either flavor will be large enough to injure or kill skiers and riders.</p>
<p>Concerns about <strong>persistent slab avalanches </strong>failing multiple feet deep and widely across steep slopes should drive terrain selection today. Caution is warranted when traveling below steep terrain because of the potential of remotely triggering avalanches from nearby areas (<a href="https://www.mtavalanche.com/node/33332"><span>Lionhead avalanche example</span></a>). Avoiding steep terrain is the management strategy for today’s persistent slab avalanche problem.</p>
<p>In areas around Bozeman and Big Sky, where more snow is actively falling, <strong>storm slab avalanches </strong>failing 1-2 feet deep are a secondary concern. Last Friday, warming temperatures trapped low-density snow below heavier snow on top, creating slabs sensitive to human triggers. On Saturday, I toured on a day off and saw shooting cracks in the new snow on every steep rollover our group approached (<a href="https://www.mtavalanche.com/node/33335"><span>observation</span></a>). Avalanche activity and cracking across the snow surface indicate instability.</p>
<p><strong>Notable Avalanches this Weekend include: </strong></p>
<ul>
<li>A 500-foot-wide natural avalanche in Argentina Bowl in the Bridger Range (<a href="https://www.mtavalanche.com/node/33370"><span>photo and details</span></a>).</li>
<li>A natural avalanche that failed on deeply buried weak layers on the north face of Mount Blackmore (<a href="https://www.mtavalanche.com/node/33360"><span>photo and details</span></a>).</li>
<li>Skiers triggered <em>many </em>collapses in the Southern Gallatin Range, with one resulting in an interesting avalanche into Specimen Creek (<a href="https://www.mtavalanche.com/node/33355"><span>photo and details</span></a>).</li>
<li>Skiers intentionally triggered an avalanche above Hebgen Lake that broke on weak layers near the ground (<a href="https://www.mtavalanche.com/node/33350"><span>details</span></a>).</li>
<li>A natural avalanche in Airplane Bowl in the Lionhead area broke 600 feet wide on buried weak layers (<a href="https://www.mtavalanche.com/node/33361"><span>photo and details</span></a>).</li>
<li>A steep slope avalanched while snowmobilers rode in a nearby flat terrain in the Lionhead area (<a href="https://www.mtavalanche.com/node/33332"><span>photo and details</span></a>).</li>
<li>A wind slab avalanche broke 200 feet wide along the top of the Ramp in the Bridger Range as skiers approached the ridgeline (<a href="https://www.mtavalanche.com/node/33322"><span>photo and details</span></a>).</li>
<li>More on the <a href="https://www.mtavalanche.com/avalanche-activity"><strong><span>Avalanche Activity Log</span></strong></a></li>
</ul>
<p><strong>So, when will conditions become safer? </strong>In the long run, deeper snowpacks tend to be more stable. In the short term, lots of snow equals lots of avalanches. Two weeks of near-constant storms have made for superb riding conditions. When it stops snowing, conditions will slowly stabilize. In the meantime, embrace the great backcountry skiing and riding on slopes less than 30 degrees (<a href="https://www.youtube.com/watch?v=wez-MVpRq5w"><strong><span>Ian’s video</span></strong></a>).</p>
<p><span>Human-triggered avalanches are likely, and the avalanche danger is CONSIDERABLE. </span></p>
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Wednesday, January 8, 2025, 7-9:30 p.m., Avy Savvy Night at the Colonial Theater, Idaho Falls. More information HERE.
Wx @0600
Sawtelle Wind is Rimed again
Island Park Snow from Black Bear SNOTEL
With decent visibility we drove up Bridger canyon to Battle Ridge to look for recent avalanches. The most noteworthy was a slab 500'+ wide, 2'+ deep in Argentina Bowl (photo), and there was an R1-R2 sized debris pile below the Saddle Peak cliffs, but clouds obscured the top of Saddle.
On Jan 5 With decent visibility we drove up Bridger canyon to Battle Ridge to look for recent avalanches. The most noteworthy was a slab 500'+ wide, 2'+ deep in Argentina Bowl (photo), 1 day old probably. Photo: GNFAC
With decent visibility we drove up Bridger canyon to Battle Ridge to look for recent avalanches. The most noteworthy was a slab 500'+ wide, 2'+ deep in Argentina Bowl (photo), and there was an R1-R2 sized debris pile below the Saddle Peak cliffs, but clouds obscured the top of Saddle. There were a few short, small wind slabs that broke along the ridgeline north of Bridger Peak. We also saw a 150' wide storm slab in Truman Gulch (photo).
We looked at the snowpack on the west side of the range in Truman Gulch. In four snowpits HS was 70cm (W, 8200'), 112cm (SW, 8400'), 135cm (NW, 8000') and 140cm (W, 8500'). The two deepest pits had ECTP28 on facets (2mm) 40cm above the ground. The other two had poor structure and soft weak snow in the bottom 30-40cm, but did not propagate in tests. Overall, the snow structure is poor and not trustworthy on the west side of the Bridgers. With more loading we could see big avalanches, whether it's this week, later this month or later in the season, and currently it seems possible a person could trigger a persistent slab avalanche here.
On the ramp there was evidence of yesterday's wind in the form of wind slabs that broke and their debris subsequently drifted over. Today wind was calm to light, and there is plenty of snow to transport if the winds do pick up. A few hours of moderate wind could easily form fresh wind slabs. Snow was starting to fall lightly in the late afternoon.
