GNFAC Avalanche Forecast for Sat Feb 20, 2021
<p>In the Bridger Range, Hyalite and near Big Sky strong wind the last two days drifted the recent 2-3 feet of snow into thick slabs. Yesterday, skiers near Mt. Blackmore reported a 3-4 foot deep, 500 foot wide natural avalanche which they had not seen on Thursday morning (<strong><a href="https://www.mtavalanche.com/node/24345">photos and details</a></strong>), and ice climbers saw a relatively large recent avalanche near Maid of the Mist (<strong><a href="https://www.mtavalanche.com/node/24340">photo and details</a></strong>). On Thursday near Bridger Peak, a large avalanche broke on a heavily wind loaded slope (<strong><a href="https://www.mtavalanche.com/node/24324">photos</a></strong>). Yesterday Ian and I snowmobiled on Buck Ridge near Big Sky. We did not see recent avalanches, but weak, sugary snow near the ground is underneath 4-6 feet of snow and can’t be trusted (<strong><a href="https://www.youtube.com/watch?v=j0UTpSilNEg&list=PLXu5151nmAvQDzKmH…;). While it is becoming more difficult to collapse this deep weak layer, recent activity shows that if you do trigger an avalanche it could be destructive and deadly.</p>
<p>Today, avoid travel on and underneath steep, wind-loaded slopes where triggering a large avalanche is likely. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other steep slopes.</p>
<p>In the southern Gallatin and Madison Range and near West Yellowstone, weak, sugary snow near the ground makes large avalanches possible. Earlier in the week these mountains did not receive the same heavy snow as the northern part of our area. This makes it less likely to trigger a large avalanche, but the potential size is the same as we have seen recently near Bozeman and Big Sky. A large snowmobile triggered slide in Cabin Creek last week is another example of what is possible (<a href="https://www.mtavalanche.com/node/24253">details</a>). Three to five inches of snow that fell since yesterday and light wind today will unlikely push the snowpack to break naturally, but could push some slopes closer to sliding under the weight of a person. Today, large avalanches are possible to trigger and avalanche danger is MODERATE.</p>
<p>In the mountains near Cooke City a snowmobile triggered avalanche on Crown Butte on Thursday is evidence that avalanches can be triggered (<a href="https://www.mtavalanche.com/images/21/snowmobile-triggered-slide-crown-…;, <a href="https://www.mtavalanche.com/images/21/snowmobile-triggered-slide-crown-…;). Recent snow and wind formed fresh drifts that can break under the weight of a skier or rider. Four to five inches of new snow today adds weight to these drifts. Be extra cautious of wind-loaded slopes, near ridgelines and below cornices. We can’t rule out the possibility of triggering a deeper slide on slopes with shallower snow (<strong>see Dave’s videos from </strong><a href="https://www.youtube.com/watch?v=tzo-kbMbDUc"><strong>Wednesday</strong>…;, <a href="https://www.youtube.com/watch?v=w4BEGFLhQWY"><strong>Thursday</strong><…;). Today the avalanche danger is rated MODERATE. Carefully evaluate the snowpack and consequences of a slide before travel on or underneath steep slopes.</p>
<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Whumph on Little Mt. Ellis
From email:"At 6450 feet on a north facing aspect on Little Mt. Ellis I found a snow depth of 75 cm. I dug a pit and got a Ct -7. Ect - 18, both failing on ground facets at 15-20 cm depth. I didn’t see any slides, but I did feel and hear one whumpf on the way up."
Whumph and small avalanche in Gallatin Canyon
"While on tour today above the canyon, we observed various snow surfaces. We found heavily windloaded slopes on E/NE aspects. Solar aspects began to develop rollers as rocks began to heat up around noon. We observed a small avalanche on E slope a drainage away, roughly 20 feet wide. While ascending a ridgeline at 7500 elevation, we had a massive woomph and crack that spread 100 feet from the ridge to a roller in the fall line."
Natural avalanche on Blackmore east face
From email: "I toured into Blackmore [2/19/21] and observed an old snow avalanche at 9600' on the east face of Mt Blackmore. I was there the day before and didn't see any evidence of avalanche activity; strong overnight winds with ample snow available for transport appeared to be enough to tip the scales."
From email: "I toured into Blackmore [2/19/21] and observed an old snow avalanche at 9600' on the east face of Mt Blackmore. I was there the day before and didn't see any evidence of avalanche activity; strong overnight winds with ample snow available for transport appeared to be enough to tip the scales." Photo: T. Guarino
From email: "I toured into Blackmore [2/19/21] and observed an old snow avalanche at 9600' on the east face of Mt Blackmore." Photo: T. Guarino
From email: "I toured into Blackmore [2/19/21] and observed an old snow avalanche at 9600' on the east face of Mt Blackmore. I was there the day before and didn't see any evidence of avalanche activity; strong overnight winds with ample snow available for transport appeared to be enough to tip the scales." Photo: T. Guarino
From email: "I toured into Blackmore [2/19/21] and observed an old snow avalanche at 9600' on the east face of Mt Blackmore. I was there the day before and didn't see any evidence of avalanche activity; strong overnight winds with ample snow available for transport appeared to be enough to tip the scales." Photo: T. Guarino
Forecast link: GNFAC Avalanche Forecast for Sat Feb 20, 2021
Natural avalanche below Maid of the Mist
An ice climber in Hyalite reported a natural D2 underneath the Maid today. Looked like it ran yesterday (2/18/21).