GNFAC Avalanche Forecast for Thu Mar 7, 2019
<p>New snow in the last 48 hours (4” in the north and 8” in the south) buried a layer of weak faceted snow that was at the surface. This layer formed over the weekend during cold, clear nights and (relatively) warmer days. Eric and I found it on Buck Ridge (<u><strong><a href="https://www.youtube.com/watch?v=EP2us1tKA0E&list=PLXu5151nmAvRNl9ku…;), the Big Sky Ski Patrol easily triggered slides on it yesterday, and a skier triggered an avalanche on it on Mt. Blackmore (<strong><a href="https://www.mtavalanche.com/node/20322">details</a></strong>), but Karl did not find it in Bacon Rind (<strong><a href="https://www.youtube.com/watch?v=5X-yLt211Vw&index=2&list=PLXu51…;). It’s prudent to assume it exists everywhere until you rule it out. Although slides will only involve new snow, they may propagate wide and catch a person off-guard. The two skiers on Blackmore were descending one at a time, a good practice that can save us when things go wrong.</p>
<p>There are two layers of concern in the snowpack, one at the top and another at the bottom. Besides the one at the top, near the ground are facets from December that are deeply buried and difficult to trigger. Ian was in Lionhead on Monday and dug to the ground to look at this deep layer and found improving stability and cautioned us to be patient as it takes days for a snowpack to adjust to such a large load (<u><strong><a href="https://www.youtube.com/watch?v=RjFLcgmfLYc&t=0s&list=PLXu5151n…;). Shallow areas, typically windblown edges of a slope, are potential trigger points for deep slides as are cornice falls.</p>
<p>Winds are gusty enough to blow snow around at the ridgetops. Shooting cracks are signs that wind drifts could slide. A zippy layer of facets under the new snow is something we have not seen this season, so dig hand pits to look for it. For today, avalanches remain possible and the danger is rated MODERATE.</p>
<p><strong>Hot Tip</strong>: Use the Regional Pages (top of the webpage) to find out what avalanche activity has been reported in the area you plan to visit.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
COOKE CITY
This Friday and Saturday, Rescue Training and Snowpack Update. Friday 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.
Skier triggered avalanche on Mt. Blackmore
From an email:
"I’d like to report an avalanche incident that occurred today, 3/6, around 2 PM on the NE face of Mt. Blackmore in the Hyalite Canyon area. On the approach, I dug a pit at 9400’ and found a very stable and deep snowpack, with a somewhat definite weak layer in between high and medium density snow about 8” deep. The layer did not slide or propagate in an extended column pit test, so my partner and I decided do ski the direct line from the summit. I skied first, making a ski cut just below the ridge line that did not result in any sloughing. I skied the line without mishap. My partner followed, traversing onto a shallow, steep pocket, releasing the avalanche. It propagated down and out in both directions, resulting in a v-shaped crown about 100’ across and 8-12” deep. The slide ran from around 9800’ to 9400’. My partner was not caught and was able to traverse out and ski down safely."
This slide on the NE face of Blackmore was triggered by the second skier. It was 8-12" deep and 100' wide and likely failed on small faceted crystals underneath the new snow. No one was caught. Going one at a time was good travel behavior that can save our lives when things go wrong.
Photo was taken on March 5 from the avalanche cycle that ended March 1. A large slab avalanche off Woody Ridge from Hayden Creek near Cooke City. Photo: K. Oberholser
Forecast link: GNFAC Avalanche Forecast for Thu Mar 7, 2019GNFAC Avalanche Forecast for Fri Mar 8, 2019
GNFAC Avalanche Forecast for Wed Mar 6, 2019
<p>Last week’s wallop of snow resulted in many avalanches, some being the largest in memory (<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche activity page</a></strong></u>). Wilson Peak in the N. Madison Range (<strong><a href="https://www.mtavalanche.com/node/20247">details</a></strong>) was one of these with a crown line about 1,000 feet wide. We read a report on Instagram (#gnfacobs) that the slope was shallow and broke on facets near the ground. On the heels of this avalanche cycle Ian dug to the ground in Lionhead on Monday (<strong><a href="https://www.youtube.com/watch?v=RjFLcgmfLYc&t=0s&list=PLXu5151n…;) to assess the stability and yesterday Eric and I rode from Buck Ridge towards Cedar Mountain (<strong><a href="https://www.youtube.com/watch?v=EP2us1tKA0E&list=PLXu5151nmAvRNl9ku…;). In both cases we found improving conditions. The videos from these field days complement each other and outline the current situation:</p>
<ul>
<li>The snowpack is adjusting to last week’s snow load and getting stronger.</li>
<li>A weak layer of facets near the ground are deeply buried in most areas, but in spots where they are shallow, like at the edges of a slope, they could still be triggered.</li>
<li>Wind-loaded slopes, especially with today’s new snow, could be triggered near the ridgelines.</li>
<li>Last night’s snowfall just buried a layer of surface hoar and/or small-grained facets that formed over the previous few days. This may be a new weak layer and could facilitate shooting cracks and thin avalanches in the new snow.</li>
</ul>
<p>In general, be wary of triggering slides on wind-loaded slopes or breaking cornices, and be mindful of sliding over thin areas of the snowpack where you could trigger an avalanche on the buried facets. For today the avalanche danger is rated MODERATE on all slopes throughout the forecast area.</p>
<p><strong>Hot Tip</strong>: Use the Regional Pages (top of the webpage) to find out what avalanche activity has been reported in the area you plan to visit.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Two avalanche fatalities in 2 days, one in CO and another in WY
On Sunday, a solo backcountry skier was caught, buried, and killed in an avalanche near Telluride, Colorado. You can read the preliminary report here. On Monday, a snowmobiler was buried and killed in a large slide at Togwotee Pass, Wyoming.
Forecast link: GNFAC Avalanche Forecast for Wed Mar 6, 2019