20-21
Doug intentionally triggered this wind-loaded sidehill. Weak, faceted snow broke under a 1' deep soft slab of windblown snow. Small avalanches like this are indicators of instability on bigger slopes. These conditions can be found throughout the southern Gallatin, southern Madison, Lionhead and Centennial Ranges. Photo: GNFAC
Beehive
Date
In Beehive again today for AAI Rec 1. Toured up to 9100 ft on the Beehive/Middle Divide. Poor structure throughout tour as expected, and we got ECTP 17-24 within the basal facets in a wind loaded area where the new snow depth was 50 cm. No natural avalanches observed, or cracking/collapsing. Still low tide and sporty on the way down.
Observer Name
Sam H
Upper Gallatin
Date
Activity
Skiing
I went on a ski around the Bighorn/Fawn Pass loop today, and had some unfortunate, but unsurprising observations. There was about 30-60 cm of snow on the ground, which consisted of a low-density slab sitting on top of unconsolidated, sugary facets. Each step forward on skis gave little resistance as I sank all the way to the ground. I observed one small, recent avalanche on a wind-loaded north aspect at 7800’, which clearly failed at the new snow/facet interface (the base is so rotten here there was an obvious difference in tone between the layers). Only one Meadow gave an audible whumph for me, but I imagine that will become more common as we get a little more SWE in the coming days. Light snowfall and moderate winds were creating drifts surprisingly quickly.
Observer Name
Sam Reinsel
Natural Loose Snow Avalanches - Beehive Basin
Beehive Basin
Northern Madison
Code
L-N-R1-D1-I
Elevation
9000
Aspect
SW
Latitude
45.32500
Longitude
-111.38300
Notes
Number caught
0
Number buried
0
Avalanche Type
Loose-snow 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
20.0 centimeters
Vertical Fall
100ft
Slab Width
50.00ft
Weak Layer Grain type
Precipitation Particles
Weak Layer Hardness
F
Attached Videos
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
Natural Loose Snow Avalanche - Divide Cirque
Divide Cirque
Northern Gallatin
Code
L-N-R1-D1-I
Elevation
9800
Aspect
SE
Latitude
45.39400
Longitude
-110.98100
Notes
Small, loose snow avalanche in the Divide Cirque in Hyalite Canyon. Released naturally sometime during the weekend's storm. These could push a skier into/ off obstacles such as trees and cliffs.
Number caught
0
Number buried
0
Avalanche Type
Loose-snow 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
15.0 centimeters
Vertical Fall
150ft
Slab Width
50.00ft
Weak Layer Grain type
Precipitation Particles
Weak Layer Hardness
F
Attached Videos
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
GNFAC Avalanche Forecast for Wed Dec 16, 2020
Snowpack and Avalanche Discussion
<p>The southern ranges received 4-6” of new snow equaling 0.2-0.4” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a> (SWE) and strong winds are actively blowing and drifting the fresh snow onto a weak foundation of sugary facets as Doug observed at Lionhead yesterday (<a href="https://www.youtube.com/watch?v=N2PYLeN5iUc"><strong>video</strong></a&…;). Snowfall and wind drifting will continue today, heightening the avalanche conditions on all slopes and creating dangerous avalanche conditions on slopes with fresh drifts where human triggered avalanches will be likely. <a>Avoid steep wind-loaded slopes and look for obvious signs of instability such as recent avalanche activity, “whumphing,” and shooting cracks from your sled or skis </a>before entering any avalanche terrain.</p>
<p>The avalanche danger is rated CONSIDERABLE wind-loaded slopes and MODERATE on all other slopes.</p>
<p>The northern ranges received 1-3” of new snow (0.1-0.2” SWE) with strong west to southwest winds. The snowpack structure is weak and human triggered avalanches are possible on slopes where the wind deposited drifts are loading the shaky foundation. Yesterday, north of Bridger Bowl, Ian and I noted that a slab was the missing ingredient before we see avalanches, our current weather will complete the recipe (<strong><a href="https://www.youtube.com/watch?v=JrjrgTLRff0">Ramp</a> </strong><a href="https://www.youtube.com/watch?v=JrjrgTLRff0"><strong>video</strong></a&…;). This same story applies to all the ranges around Bozeman and Big Sky (<a href="https://www.youtube.com/watch?v=cUnquoQ5kXU"><strong>Beehive video</strong></a>, <a href="https://youtu.be/aqBSydiYMYk"><strong>Hyalite video</strong></a>, <a href="https://www.youtube.com/watch?v=NDfD3-tTguk"><strong>Saddle Peak video</strong></a>, <a href="https://www.youtube.com/watch?v=4quJW8upKQg"><strong>Buck Ridge video</strong></a>). On non-wind-loaded slopes, the new snow’s weight is not enough to increase the avalanche danger and human triggered avalanches will be limited to isolated areas in steep, rocky terrain. Watch for signs of instability and dig a quick snowpit before entering any avalanche terrain (<a href="https://www.youtube.com/watch?v=Gk8W8nlUMpw&list=PLXu5151nmAvQDzKmH…;
<p>Today the avalanche danger is rated MODERATE on wind-loaded slopes and LOW on all other slopes.</p>
<p>Lacking the widespread weak layers found in the rest of our advisory area, the snowpack in Cooke City will support yesterday’s 3” of new snow (0.2” SWE). Avalanches will be small and confined to the recent snow in steep and extreme terrain. These slides can have outsized consequences if they push a rider or skier into terrain traps such as rocks, trees, and cliffs. Assess the snowpack before entering avalanche terrain and use safe travel practices by only exposing one person at a time and carrying all avalanche rescue equipment.</p>
<p>Today the avalanche danger is LOW in the mountains around Cooke City.</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>
Upcoming Avalanche Education and Events
See our education calendar for an up to date list of all local classes. Here are a few select upcoming events and opportunities to check out:
Wyoming Creek off Republic Ridge
Date
Activity
Skiing
80cm snowpack at 9100 feet, 20 degree, 280 azimuth, stable
Region
Cooke City
Location (from list)
COOKE CITY
Observer Name
D Carroll