19-20

Collapse near Ross Peak

Ross Peak
Bridger Range
Code
Latitude
45.85910
Longitude
-110.95500
Notes

After getting unstable snowpack test results, skiers on 3/27/2020 got a collapse on facets over a crust buried about a foot deep, near Ross Peak in the Bridger Range.

Number of slides
0
Number caught
0
Number buried
0
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year

GNFAC Avalanche Forecast for Sat Mar 28, 2020

Snowpack and Avalanche Discussion

<p>Avalanches can break today on weak layers buried 1-2 ft deep underneath this week’s snow. These weak layers have been found across southwest Montana and we’ve seen quite few avalanches breaking on them (<a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a>). On Thursday, skiers in Hyalite triggered a slab that broke 2 ft deep on a north facing slope in the Twin Falls basin (<a href="https://www.mtavalanche.com/images/20/skier-triggered-slide-hyalite">ph…;).</p>

<p>Doug and Dave took down the Taylor Fork and Lionhead weather stations yesterday. In both areas they got unstable snowpack test results on the weak layers in the upper snowpack (<strong><a href="https://www.youtube.com/watch?v=ZkyjbN1sWl0&amp;list=PLXu5151nmAvSbcbVf…;). In the Taylor Fork the weak layer was sitting above a crust, while there was no crust at Lionhead. In some area the weak layer is near surface facets and in others it is surface hoar. The grain type of the weak layer doesn’t really matter. The important thing is that if the weak layers are there, they’ll be just beneath the new snow. Use an Extended Column Test to look for and test the weak layer before getting onto a steep slope. Yesterday, multiple groups got unstable test result across the area and backed off steeper lines. Follow their example. The more deeply these weak layers are buried, the more problematic they will be, which means that wind-loaded slopes remain more worrisome than other slopes (<a href="https://www.mtavalanche.com/images/20/cornice-growth-bridger-ridge"><st…;).</p>

<p>Clouds and temperatures in the 20s F should keep the wet snow at bay today.</p>

<p>The <a href="https://covid19.mt.gov/Portals/223/Documents/Stay%20at%20Home%20Directi… at home order</a> that goes into affect today across Montana specifically discourages “outdoor recreation activities that pose enhanced risks of injury or could otherwise stress the ability of local first responders to address the COVID-19 emergency (e.g., backcountry skiing in a manner inconsistent with avalanche recommendations or in closed terrain)”. Get out and enjoy the fresh air, but please dial back your objectives, slow down, and work to minimize the risk of injury or need for rescue.</p>

<p>Throughout our advisory area, the avalanche danger is rated MODERATE.</p>

<p>We plan to end daily avalanche forecasts on Sunday, April 5<sup>th</sup> and continue with general bulletins every Monday and Friday through April. We have taken down most weather stations and will no longer receive observations from guides and ski patrol. We need help gathering field data. Please send us your observations no matter how brief. You can fill out an observation form, email us (mtavalanche@gmail.com), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

The avalanche education season is winding down, but you can still find a few courses offered by other providers on our website on the Events and Education Calendar.

Skier triggered slide in Twin Falls Basin

Hyalite - main fork
Northern Gallatin
Code
SS-ASu-R2-D2
Elevation
9000
Aspect
N
Latitude
45.41740
Longitude
-110.98900
Notes

From obs: Small D2 avalanche triggered while assessing the slope on a due-north facing aspect on a roughly 35-40 deg. slope at ~9000 ft. near Arden Lake in the Twin Falls drainage off the Main Fork of Hyalite. ....  Had about a 2 ft deep, 30 ft-long crown. The bed surface was not clearly a sun-crust and was of low quality and remained relatively soft to ski on after the slide. There were crystals above that may be classified as facets, maybe 1mm dia. It seemed to have gone on a compacted layer that the 18" of fresh had weighted."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural avalanche in Cooke

COOKE CITY
Cooke City
Code
SS-R2-D1.5
Latitude
45.02020
Longitude
-109.93800
Notes

From email on 3/27/2020 : "natural slab avalanche I observed today near Cooke City.  An easterly aspect around 9,400'.  I'd estimate the crown to be 2-3' deep and about 100' wide.  Looks like it was triggered by a cornice fall (2-3 days ago?)."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
R size
2
D size
1.5
Slab Thickness
24.0 inches
Slab Width
100.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From email on 3/27/2020 : "natural slab avalanche I observed today near Cooke City.  An easterly aspect around 9,400'.  I'd estimate the crown to be 2-3' deep and about 100' wide.  Looks like it was triggered by a cornice fall (2-3 days ago?)."

Photo: B. Fredlund

Cooke City, 2020-03-28