21-22

GNFAC Avalanche Forecast for Fri Apr 22, 2022

Snowpack and Avalanche Discussion

<p>The avalanche equation is not complicated this weekend. On Friday morning, a major spring storm is beginning to impact the area with 10-20+” of snow likely by Saturday night. This will create dangerous avalanche conditions. Winds will increase Saturday and drift snow into deeper and more cohesive slabs that could break over wide areas. Avalanches are likely within the new and wind drifted snow and will be large enough to injure or kill riders and skiers.</p>

<p>Last weekend a similar spring storm resulted in natural avalanches in the Bridger Range (<a href="https://www.mtavalanche.com/images/22/natural-avalanches-northern-bridg…;) and Cooke City (<a href="https://www.mtavalanche.com/images/22/natural-avalanche-fin"><strong>ph…;). Outside of the advisory area in the East Rosebud drainage, five skiers from two separate groups were caught and partially buried by a natural loose snow avalanche while they were ascending a steep couloir. Luckily, no one was injured (<a href="https://www.mtavalanche.com/node/26486"><strong>details</strong></a&gt;). Expect similar or larger avalanches this weekend.</p>

<p>On Sunday, temperatures will rise into the mid to upper 30s F and the powerful spring sun will come out. This will result in an increasing wet snow avalanche danger on slopes where the snow surface gets moist (<a href="https://www.youtube.com/watch?v=JqwSknw4e_E&amp;list=PLXu5151nmAvT1nrM2…;). Move to shadier slopes or stay out of steep terrain if you notice the snow surface getting wet.</p>

<p>Indicators of instability such as recent avalanches, cracking and collapsing provide all the information you need about the snowpack and should keep you in lower angle terrain. Without these obvious signs, a careful assessment that tests for instabilities in the upper 3’ of the snowpack is necessary if you plan to go into terrain steeper than 30 degrees. Always follow safe travel protocols by skiing and riding with a partner, carrying a beacon, shovel and probe and exposing only one person at a time to avalanche terrain.</p>

<p>We will issue spring snowpack and weather updates each Monday and Friday through April, or as needed, and we will share relevant avalanche and snowpack information on our website and social media. 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>

Announcements, Avalanche Education and Events

Bridger Bowl is closed, and backcountry conditions exist. There is no avalanche mitigation or ski patrol rescue. In case of emergency, call 911. Please stay clear of work areas, snowmobiles, chair lifts and other equipment. Without the daily avalanche mitigation efforts of the ski patrol, backcountry conditions now exist within the boundaries of Bridger Bowl (video).

Natural large slab in Mineral Mtn.

Mineral Mountain
Cooke City
Code
SS-N-R2-D2-I
Elevation
9800
Aspect
E
Latitude
45.03030
Longitude
-109.99800
Notes

On 4/18/22 we saw a large natural slab on east facing Mineral Mtn. around 9,800', on a wind loaded slope below cliffs. Happened yesterday or maybe this morning. Photo: GNFAC

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
2
D size
2
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
12.0 inches
Vertical Fall
800ft
Slab Width
210.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Rollerballs, Pinwheels and Wet Loose near Cooke

Sheep Creek
Cooke City
Code
WL-N-R1-D1-S
Elevation
8800
Aspect Range
S, SE, SW, E, NE
Latitude
45.03440
Longitude
-109.98400
Notes

On 4/18/22 near Cooke City we witnessed natural rollerballs and pinwheels by 11 am, and a couple wet loose slides below cliffs on southerly slopes around noon, and were able to easily trigger pinwheels on west-southwest aspects around 1230-1pm.

Number of slides
4
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
S - Avalanche released within new snow
Problem Type
Wet Snow
Slab Thickness
3.0 inches
Vertical Fall
100ft
Slab Width
10.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

On 4/18/22 near Cooke City we witnessed natural rollerballs and pinwheels by 11 am, and a couple wet loose slides below cliffs on southerly slopes around noon, and were able to easily trigger pinwheels on west-southwest aspects around 1230-1pm. Photo: GNFAC

Cooke City, 2022-04-20

Natural and skier triggered small new snow slides

COOKE CITY
Cooke City
Code
SS-N-R1-D1-I
Elevation
9500
Aspect Range
E, N, NE
Latitude
45.02020
Longitude
-109.93800
Notes

On 4/17/22 near Cooke City we saw a couple natural 2-4" deep, 10' wide slabs on small hills lower down (pictured); natural 6-16" slabs on heavily wind loaded slopes on east aspect of Sheep Mtn., north face of Miller and east Wolverine mostly D1-1.5 (no photos); and two skier triggered D1.5 loose snow/storm slabs on the east aspect of Miller Ridge (no photo).

Number of slides
8
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
6.0 inches
Vertical Fall
100ft
Slab Width
20.00ft
Weak Layer Grain type
Precipitation Particles
Slab Layer Grain Type
Precipitation Particles
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year