23-24

Remote trigger avalanche at Picket Pin

Other place
Out of Advisory Area
Code
HS-AMr-R3-D3-O
Latitude
45.65530
Longitude
-110.55800
Notes

From FB message 2/11/24: "Picket Pin Mountain yesterday. We triggered it but weren't anywhere near it"

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
3
D size
3
Bed Surface
O - Old snow
Slab Thickness
36.0 inches
Vertical Fall
700ft
Slab Width
1000.00ft
Images
Picket Pin Avalanche - 10 Feb
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
23-24

Wet snow, dry snow, weak snow

Date
Activity
Skiing

We went on a safari of different snow conditions at Beehive today. We toured up to the prayer flags, looked into the top of Bear Basin on southeast and northeast aspects, and then returned to Beehive through the north edge of Tyler's. We dug a pit in the starting zone of Tyler's and were a bit surprised by an ECTP11 on basal depth hoar. There were percolation columns through the upper half of the snowpack and the lower two thirds of the snowpack were moist. You could make a snowball. The depth hoar remains very weak and F+ hardness. The stout melt freeze crust was 3" thick on the southwest aspect.

Surface snow conditions varied wildly as is often the case in the spring. There was cold powder on the northern half of the compass. The crust had broken down by 11 AM on the southeast aspect and the top 3-5" were wet and rollerballs were easy to push downhill. The southwest aspect was just starting to soften as we left at 1 PM. If we continue to get good overnight freezes, we will only have to worry about wet, loose snow avalanches. Wet slab activity should be limited if there is any. 

Region
Northern Madison
Location (from list)
Beehive Basin
Observer Name
David Zinn

The Throne Update

Date
Activity
Skiing

Rode into The Throne via Battle Ridge on Sun. Trail in is heavily bumped and dirt starting to show. Guessing it will be about finished by the end of the week with the higher temperatures.      Skied a couple of laps on The Throne. Top layer was soft/slushy, or corn like, but the rest of the snowpack was one finger hardness until the bottom 10". Bottom of the snowpack remains rotten.    We saw two small point releases that were maybe 15' wide, caused by warming. Otherwise the snowpack felt stable in our area. 

Traveled N to a subridge of Naya Nuki and found similar results. No recent avalanche activity noted. 

Region
Bridger Range
Location (from list)
The Throne

GNFAC Avalanche Forecast for Mon Mar 18, 2024

Snowpack and Avalanche Discussion

<p>Large avalanches breaking deep in the snowpack on persistent weak layers and wet, loose snow avalanches are possible in the mountains across the advisory area.</p>

<p>The likelihood of triggering an avalanche deep in the snowpack on persistent weak layers has decreased over the last week, but the consequences remain as severe as before. Ask the rider in the Taylor Fork who escaped a slide that broke 2-4 feet deep on Sunday and the skier who, less than 30 miles outside the advisory area, remotely triggered a large avalanche that snapped trees like pick-up sticks on Friday if they remain possible. You will hear a resounding yes (<a href="https://www.mtavalanche.com/node/31479"><strong><span>Taylor Fork photo and details</span></strong></a>, <a href="https://www.mtavalanche.com/node/31460"><strong><span>Lawnmower details and photos</span></strong></a>). A few days of melt-freeze cycles have not fundamentally changed the structure of the snowpack. Yesterday, a skier in Beehive Basin triggered a collapse on a small, low-angle slope with a frozen melt-freeze crust that shifted a few inches downhill (<a href="https://www.mtavalanche.com/node/31493"><strong><span>observation</span…;). Currently, accurately assessing the likelihood of a slide on the slope scale is difficult to impossible so careful terrain evaluation is our best tool. Add certainty to your day by avoiding slopes over 30 degrees (<a href="https://youtu.be/__KumkBkUJ4"><strong><span>Cooke City video</span></strong></a>). Lower-angle avalanche terrain and slopes with clean runouts and without terrain traps are the best options if you choose to play the odds. Follow safe travel practices, including traveling one at a time while a partner remains in position for rescue.</p>

<p>The danger of wet snow avalanches will increase throughout the day as high temperatures reach the 40s and 50s F. Alex described from the Taylor Fork how a frozen melt-freeze crust is indicative of wet snow <em>stability</em> and a snow surface with more than a few inches of wet slushy snow indicates wet snow <em>instability</em> (<a href="https://youtube.com/shorts/yt6kIzWXpRc"><strong><span>video</span></str…;). Get off any steep terrain before the surface snow becomes unstable, and remember this process will happen faster in lower elevations, so ensure safe egress options. With a solid overnight freeze, these avalanches should remain relatively small, but they can pack a punch (<a href="https://www.mtavalanche.com/images/24/wet-loose-snow-avalanche-crown-bu… Butte wet snow avalanche</span></strong></a>, <a href="https://youtu.be/__KumkBkUJ4"><strong><span>Cooke City video</span></strong></a>).</p>

<p>The avalanche danger is rated MODERATE.</p>

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Quick notes on wet snow &quot;stability&quot;

Date

In my videos I have somewhat implied that slopes are "stable" while they have a solid melt-freeze crust, but that is only in regards to wet snow. This evening I was wondering if a (mostly dry) avalanche could be triggered multiple feet deep on the pwl on a slope with a 1-2" frozen crust on the surface? Seems possible, especially this year. (Maybe the crust would make triggering slightly more difficult, but promote propagation?) Then Nelson's observation came in and it sounds like he had a large collapse a couple feet deep on a slope with a frozen crust on the surface...

I just wanted to urge us to be cautious saying or writing, "slopes with a frozen surface are good to go", despite what I may have said in a video. A frozen surface cab rule out the wet snow danger, but you still have to assess the potential for avalanches to break on deeper buried weak layers.

Observer Name
Alex Marienthal
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