20-21

From obs: "I went up Blackmore [1/9/21]... A pit on a south aspect at 9400’ had 100 cm, and failed at ECTP22 on large, loose facets underlying a crust about 50 cm down. A pit on a north aspect at 9400’ had 105 cm and failed at ECTP20 on the same layer, although the crust was close to nonexistent on this aspect. The snowpack overall was weaker and less consolidated here. A pit on an east aspect at 9400’ had 135 cm, and failed at ECTP25 on the same layer as the other two. I experienced a couple collapses while in shallower, treed areas on north and south aspects today.

Northern Gallatin, 2021-01-09

Blackmore

Date
Activity
Skiing

I went up Blackmore today, to follow up on some positive results on Palace Butte yesterday that I thought I had reason to question. Today, I found something more in line with what I expected in the snowpack.

A pit on a south aspect at 9400’ had 100 cm, and failed at ECTP22 on large, loose facets underlying a crust about 50 cm down.

A pit on a north aspect at 9400’ had 105 cm and failed at ECTP20 on the same layer, although the crust was close to nonexistent on this aspect. The snowpack overall was weaker and less consolidated here.

A pit on an east aspect at 9400’ had 135 cm, and failed at ECTP25 on the same layer as the other two.

I experienced a couple collapses while in shallower, treed areas on north and south aspects today. I did not observe any recent natural activity, but do not trust the snow very much. There was a lot of great skiing to be had on 20-30 degree slopes.

Region
Northern Gallatin
Location (from list)
Mt Blackmore
Observer Name
Sam Reinsel

Small Natural Avalanche NW of Cooke

COOKE CITY
Cooke City
Code
SS-N-R1-D1
Elevation
9700
Aspect
E
Latitude
45.02020
Longitude
-109.93800
Notes

Natural avalanche NW of Cooke City on an E, SE aspect around 9,700'.

Photo: B. Fredlund

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Sat Jan 9, 2021

Snowpack and Avalanche Discussion

<p>Large, dangerous, human triggered avalanches are likely today. Yesterday, an avalanche was triggered remotely (from a distance) in Cinnamon Creek (<a href="https://www.mtavalanche.com/node/23650"><strong><u>details</u></strong>…;), and there were many large collapses reported in the northern Madison and Bridger Ranges including some cracks breaking 300 ft away from the trigger point (<a href="https://www.mtavalanche.com/node/23646"><strong><u>details</u></strong>…;, <a href="https://www.mtavalanche.com/node/23653"><strong><u>details</u></strong>…;). Yesterday, Alex and I saw 9 human triggered and natural avalanches on Buck Ridge that broke since Tuesday. A slide triggered on Thursday afternoon broke 2 ft deep and 1000 ft wide (<a href="https://www.youtube.com/watch?v=VCI4BiZ14CY"><strong><u>video</u></stro…;, <a href="https://www.mtavalanche.com/images/21/beaver-creek-wide-slide-pano"><st…;).</p>

<p>All of this activity is happening on the weak snow at the ground. We’re on the tail end of the largest loading event of the year. The snowpack is telling us it needs time to adjust and stabilize. With snow this weak, stabilization is a slow process. For now, the snowpack remains touchy. Stay off of and out from under steep slopes. You can trigger slides from the bottom and they may break wider than you’d expect.</p>

<p>Human triggered avalanches are likely and the avalanche danger is CONSIDERABLE.</p>

<p>The overall story is the same in the northern Gallatin Range, aside from recent snowfall totals. There is weak snow at the ground capped by recent snowfall. With less new snow, the snowpack is not as widely reactive, but if triggered a slide will be just as dangerous. Watch for and search out signs of instability before exposing yourself to steep slopes. The avalanche danger is MODERATE today.</p>

<p>Yesterday, a group of skiers triggered an avalanche on The Fin, near Cooke City (<a href="https://www.mtavalanche.com/images/21/skier-triggered-fin"><strong><u>p…;, <a href="https://www.mtavalanche.com/node/23644"><strong><u>details</u></strong>…;). Three people were caught and partially buried. One skier was buried face down and briefly lost consciousness while another was injured severely enough to require a helicopter evacuation. In a separate incident, a skier triggered and was carried by a slide that broke 2 ft deep and ran 500 vertical ft on the south face of Meridian Peak (<a href="https://www.mtavalanche.com/node/23651"><strong><u>details</u></strong>…;). While weak snow is not widespread, clearly some slopes harbor an unstable recipe. These avalanches are good reminders to stay conservative in your terrain selection, vigilant in your snowpack assessment,&nbsp;and diligent with your safe travel protocols. Only expose one person at a time to steep slopes. Today, human triggered avalanches are <strong><em>possible</em></strong> and the avalanche danger is rated MODERATE.</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><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

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Rider triggered large, wide slide on Buck Ridge

Buck Ridge
Northern Madison
Code
HS-AMu-R4-D2-O
Elevation
9350
Aspect
NE
Latitude
45.17190
Longitude
-111.38000
Notes

We saw this relatively very large, full width avalanches that was triggered on January 7, 2021. It broke on weak, sugary snow below hard wind drifted snow and recent new snow.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
4
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
24.0 inches
Vertical Fall
100ft
Slab Width
1200.00ft
Weak Layer Grain type
Faceted Crystals
Weak Layer grain size
2.00mm
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year