20-21
Sage Basin Avalanche
Taylor Fork
Southern Madison
Code
SS-NC-R3-D2-O
Elevation
9250
Aspect
NE
Latitude
45.06070
Longitude
-111.27200
Notes
This avalanche failed on a heavily wind-loaded slope in Sage Basin along the ridgeline. It may have initiated as a cornice fall or a wind- slab , but it broke down to deeply buried facets. Even though it was a small slope, the slide had enough power to knock down a tree and piled debris deeply at the bottom of the slope.
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
36.0 inches
Vertical Fall
100ft
Slab Width
150.00ft
Images
Attached Videos
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
This recent avalanche failed on a heavily wind-loaded slope in Sage Basin along the ridgeline. It may have initiated as a cornice fall or a wind-slab, but it broke down to deeply buried facets. Even though it was a small slope, the slide had enough power to knock down a tree and piled debris deeply at the bottom of the slope. Photo: GNFAC
Avalanche Details: Sage Basin Avalanche
Southern Madison, 2021-02-28
There was 6' of snow off the ridge in the Bridger Range on an east facing slope. The top 2 feet were recent wind drifting that broke clean in our stability test which indicated unstable conditions (ECTP18). We expect similar conditions and instability with wind-loaded slops throughout our forecast area. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Mon Mar 1, 2021
In the last 24 hours (2/28) 12" of low density powder and 40-50 mph west wind made it easy to trigger wind-drifted snow. Alex kicked these drifts which cracked and moved. We expect similar conditions and instability with wind-loaded slops throughout our forecast area. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Mon Mar 1, 2021
Skier triggered cornice N of Peters Point, adjacent to Bridger Bowl boundary
BRIDGER RANGE
Bridger Range
Code
SS-ACu
Latitude
45.85120
Longitude
-110.94800
Notes
From obs: "Observed a small avalanche while teaching a rec. 1 today for MSU. The light was too flat to see a crown. Based on the light wind, ski patrol obs. and our moving obs., I hypothesize that it was a dry, loose avalanche. L-N-R1-D1.5-I."
Patrol reported: "A midday report from [a skier] that he had released the Duane's C Cornice (out of bounds to the north) as he travelled to the ramp had us looking for any tracks below, none were observed. It looked to step down and pull some older layers as it went through the lower pinch."
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall triggered by human or explosive action
Trigger Modifier
u-An unintentional release
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
GNFAC Avalanche Forecast for Sun Feb 28, 2021
Snowpack and Avalanche Discussion
<p>Yesterday’s snow favored the Bridger Range and West Yellowstone with 10-12” of snow equal to 0.7” of snow water equivalent (SWE). Elsewhere got 3-6” of snow equal to 0.3-0.5” of SWE. Wind increased last night and is drifting the new snow into fresh slabs. These slabs are easy for a rider or skier to trigger, and their additional weight increases the chances to trigger a deeper avalanche on weak, sugary snow near the ground. Yesterday I found this weak snow buried 3-4’ deep on Mt. Ellis (<strong><a href="https://www.mtavalanche.com/images/21/mt-ellis-weak-snow-ground">photo<…;, <strong><a href="https://www.mtavalanche.com/images/21/mt-ellis-n-ridge-profile-27-feb">… profile</a></strong>). It collapsed and propagated in most stability tests, but just knowing it exists on almost every slope was enough to avoid slopes steeper than 30 degrees. Avalanches on this layer are becoming more difficult to trigger, but they will be deep and wide, destructive, and potentially deadly (<a href="https://youtu.be/Ychm42ihtjk"><strong>Blackmore video</strong></a>, <a href="https://youtu.be/65JO-4w4qXo"><strong>McAtee Basin video</strong></a>).</p>
<p>Today fresh wind slabs are likely and will be larger where more new snow fell. Any amount of wind-loading with the weak snow buried deep in the snowpack is reason to step back to more conservative terrain selection. Avoid wind-loaded slopes, and remain extra cautious of all slopes steeper than 30 degrees. The avalanche danger is rated CONSIDERABLE on wind-loaded slopes and MODERATE on all other slopes.</p>
<p>Near Cooke City, weak snow near the ground is less widespread, but remains a concern in addition to avalanches breaking in recently drifted snow. Recent avalanche activity and signs of instability have been on either heavily wind-loaded slopes or slopes with a relatively shallower snowpack (5-6 feet). Slopes with both are the most unstable. A natural avalanche in Hayden Creek earlier in the week was on a wind-loaded slope that has avalanched several times already this year keeping the snowpack unusually thin and weak (<a href="https://www.mtavalanche.com/node/24432"><strong>details</strong></a>). Yesterday skiers in Republic Creek had unstable test scores (ECTP 30) on a weak layer buried 2.5 feet deep in a 5-6 foot deep snowpack. These conditions are not widespread, but are where avalanches are possible to trigger today. Assess for and avoid steep slopes that are heavily wind-loaded or suspect of having buried weak layers. Today, avalanches are possible to trigger and the avalanche danger is MODERATE.</p>
The Beacon Park at Beall Park in Bozeman is running!
The Friends of the Avalanche Center in partnership with the City of Bozeman put in a Beacon Park at Beall Park. It is located on the north side of the Beall building between N. Bozeman Ave. and the ice rink.