24-25

GNFAC Avalanche Forecast for Wed Nov 6, 2024

Snowpack and Avalanche Discussion

<p>This week’s storm changed the avalanche picture. Backcountry travelers will find a layered snowpack capable of producing avalanches across the forecast area in most mid to upper-elevation terrain. Storm totals since Saturday in the mountains around Bozeman and Big Sky are 20-24” (1.3-1.8” of <a href="https://avalanche.org/avalanche-encyclopedia/#snow-water-equivalent-swe… water equivalent-SWE</span></a>), with 10-14” near West Yellowstone and Island Park (1.1-1.4” SWE) and 7” (0.7” SWE) in Cooke City. Visit our <a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><span>wea… log</span></strong></a> for a daily breakdown. As Alex discussed in a short <a href="https://www.youtube.com/watch?v=Fv-xejsRWkg"><strong><span>video</span>…;, the snow on the ground is likely the foundation of this season’s snowpack.</p>

<p>Expect and prepare for avalanches within the new and wind-drifted snow. Slides will be likely at the tail end of this week’s storm, especially around Bozeman and Big Sky, where the most snow fell and winds gusted 40-60 mph. Without additional loading, stability will improve throughout the week. However, uncertainty is high this time of year as we learn the specifics of a new snowpack. Employ an information-gathering mindset and a healthy distrust for steep snow-covered slopes. Signs of instability, such as recent avalanche activity, shooting cracks and collapsing, are red flags and reasons to avoid avalanche terrain. Dig a quick snowpit to assess for instability when obvious signs are not present.</p>

<p>Early season avalanches on the Sphinx last weekend (<a href="https://www.mtavalanche.com/node/32052"><strong><span>photos and details</span></strong></a>), outside the advisory area on Emigrant Peak on Monday (<a href="https://www.mtavalanche.com/node/32047"><strong><span>photo and details</span></strong></a>), along with an observation of signs of instability on Mount Blackmore from Saturday (<a href="https://www.mtavalanche.com/node/32041"><strong><span>observation</span…;) are clear indicators that avalanche season is here. Whether hunting, skiing, riding, climbing or sledding, if you cross a steep slope where snow is deep enough to cover the grass and rocks, you may be able to trigger a slide. Carry rescue gear (beacon, shovel and probe) and follow safe travel procedures in and around avalanche terrain.</p>

<p>Public observations are incredibly valuable as we develop a picture of the season's snowpack. Please contribute to our community’s knowledge by <a href="https://www.mtavalanche.com/node/add/snow_obs"><strong><span>submitting your observations</span></strong></a>, and look through our <a href="https://www.mtavalanche.com/snow-observations-list"><strong><span>obser… page</span></strong></a> for additional information before your next backcountry adventure.</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar

Wednesday, November 13, 4-8 p.m., Montana State University Snow and Avalanche Workshop. Open to the public.

Climber triggered wind slabs at the Sphinx

Sphinx Mountain
Southern Madison
Code
HS-AF-R2-D1-I
Elevation
9600
Aspect
NW
Latitude
45.15820
Longitude
-111.47700
Notes

Triggered a small wind slab:

-9600'

-N aspect on the NW ridge of Sphinx Mountain 

-Strong SW wind

-Noticed other small crowns, likely triggered from another party traversing the north-facing bowl at similar elevations

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Foot penetration
R size
2
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
10.0 inches
Slab Width
25.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs.: "Triggered a small wind slab: -9600' -N aspect on the NW ridge of Sphinx Mountain -Strong SW wind

-Noticed oth er small crowns, likely triggered from another party traversing the north-facing bowl at similar elevations" Photo: S. Bonucci

Southern Madison, 2024-11-05

Wind Slabs at the Sphinx

Date
Activity
Ice Climbing

Triggered a small wind slab:

-9600'

-N aspect on the NW ridge of Sphinx Mountain 

-Strong SW wind

-Noticed other small crowns, likely triggered from another party traversing the north-facing bowl at similar elevations

Region
Southern Madison
Location (from list)
Sphinx Mountain
Observer Name
Steph Bonucci

Early season avalanche, outside advisory area

Out of Advisory Area
Code
N-R2-D2
Elevation
9400
Aspect
E
Latitude
45.30290
Longitude
-110.63500
Notes

Avalanche observed on Chico Baldy above Mill Creek in Paradise Valley.  East aspect at about 9400'. Possibly a wind slab but hard to tell

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
R size
2
D size
2
Problem Type
Wind-Drifted Snow
Vertical Fall
800ft
Slab Width
70.00ft
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year