23-24

Observations from The Playground

Date
Activity
Skiing
Snowboarding

We toured from the Bracket Creek trailhead to The Playground.  

It snowed all day, predominantly S-1 with a few notable pulses of S-2.  

Winds were super elevation-dependent, with moderate (gusts to strong) upslope winds (E-NE) up until about 6500', moderate upslope winds from approx. 6500'-7300', and light and at times variable south-westerlies up until our high point at 8200'.  We saw very little wind effect above 7300' and we did not travel on any wind-loaded steep slopes during our tour. 

By 5:30 PM, there was 14-16" of new snow at 7000' and 22-24" at 8000'. Below the new snow was a stout and supportable melt-freeze crust. 

At the beginning of the day, we found the storm snow to be relatively low-density and unconsolidated, except for a 1-2" super soft slab capping the new snow in most locations we traveled. That thin soft slab got capped with another 3-5" of low-density snow that fell by the end of the day.

Though we could get small columns in hand pits to slide on the crust below, they lacked cohesion and broke apart when moved. We experienced only minor cracking on the ascent. The surface snow sluffed easily during our descents, but did not entrain much volume. In the wind-sheltered zones through which we traveled, neither test slopes, uptrack tests, nor ski descents produced any obvious signs of instability. 

 

Region
Bridger Range
Location (from list)
Playground
Observer Name
Josh Lipkowitz

Poor test score Mt Ellis

Date
Activity
Skiing

Performed an ECT test high on the east face of Mt Ellis at 12:30 pm on 4/7/2024. Found 8” of medium density powder on a 3” ice crust with 2’ of lowish density slush beneath the crust. Got an ECTP 14 that broke at the ground. The ice crust seemed to hold the slope together well enough to support a skiers weight yesterday. Concerned that additional warming today could make this slope dangerous.

Region
Northern Gallatin
Location (from list)
Mt Ellis

GNFAC Avalanche Forecast for Mon Apr 8, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Near Bozeman and Big Sky the snow that fell over the weekend creates heightened avalanche conditions and you can trigger avalanches that break within or below this snow. This afternoon the danger will increase due to sunshine and temperatures above freezing making large wet loose avalanches likely.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Over the weekend the Bridger Range got over 2 feet of snow equal to 2.5-3.0” of snow water equivalent (SWE), and Big Sky and Hyalite got 7-12” equal to 0.7-1.2” SWE. Yesterday in the Bridgers, Dave and I measured the snow and investigated stability at </span></span></span></span></span></span><a href="https://youtu.be/iO3EWqb0oqg?feature=shared"><span><span><span><strong>… Ramp (video)</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://youtu.be/Fjo1jg8p49M?feature=shared"><span><span><span><strong>… Throne (video)</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, and there were many skier triggered slides that broke within the new snow throughout the range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/skier-triggered-slab-wolverine"><… photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31775"><span><span><span><strong><span… photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31777"><span><span><span><strong><span… Lake photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31789"><span><span><span><strong><span…. Bridgers photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/skier-triggered-avalanche-banana-… Peak</span></span></u></span></strong></span></span></span><span><span><span><span><span><u><span><span> </span></span></u></span></span></span></span></span><span><span><span><strong><span><u><span><span>photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).&nbsp;</span></span></span></span></span></span><span><span><span><span><span><span>Similar avalanches can be triggered today. </span></span></span></span></span></span><span><span><span><span><span><span>Although these types of instabilities typically heal quickly, today you should steer clear of fresh drifts and carefully assess the potential for the new snow to slide. Choose smaller slopes and slopes without cliffs, trees, rocks or gullies that would increase the chances of being injured or killed in any size slide.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>When the sun comes out stability will quickly decrease and make wet avalanches that can run long distances. These slides could become large where more snow fell, and even a small wet slide will easily knock you over or carry you down a steep slope. Plan to be off of and out from below steep slopes before the recent snow becomes moist or wet. A sticky snow surface is a sign to find shadier or lower angle slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanches breaking on deeper weak layers are unlikely, but not out of the question on higher, shady slopes that didn’t get as wet last week. Dig down a few feet to check for buried weak layers before getting onto steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Today the avalanche danger starts at MODERATE and will increase to CONSIDERABLE for wet snow avalanches later in the day.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near West Yellowstone, Island Park and Cooke City less snow over the weekend and more clouds today will minimize the threat of wet snow avalanches compared to other areas. Over the weekend these mountains got 4-7” of snow equal to 0.4-0.7” SWE. You can trigger avalanches where new snow is drifted into thicker slabs, and wet loose avalanches will be possible if the sun comes out (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=Qcwz2QLOKxE&amp;list=PLXu5151nmAvSH326z…;). Wind slabs or wet loose avalanches could easily slide on the hard melt-freeze crust below.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Watch for cracking across the snow surface as a sign unstable drifts exist, and if the snow surface gets moist expect wet loose avalanches. Choose slopes without trees, cliffs or other terrain traps that would increase the chances of being injured in even a small slide. Deeper avalanches are unlikely, but not impossible. If you are riding steep, consequential slopes it is a good idea to dig down a few feet to look for weak layers and assess snow stability. Avalanche danger is MODERATE near Cooke City, West Yellowstone, Island Park, and in the southern Madison and southern Gallatin ranges.</span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

Hyalite Road Closure: Hyalite road is closed to ALL MOTORIZED VEHICLES until the morning of May 16. This is a regular annual road closure to reduce road damage during the spring thaw. Bicycle and foot traffic are allowed. Contact the Bozeman FS Ranger District for more info.

Skier triggered avalanche in Banana couloir

Ross Peak
Bridger Range
Code
SS-AS-R2-D1.5-S
Elevation
8200
Aspect
SE
Latitude
45.85860
Longitude
-110.95600
Notes

From IG message: “Rode the banana today.. lots of fast moving sluff. Had a mid elevation pocket pop. New snow seemed to have bonded well, the spot that did pop had formed into 12” slab below rock face. Little to no signs of instability.”

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
R size
2
D size
1.5
Bed Surface
S - Avalanche released within new snow
Problem Type
New Snow
Slab Thickness
12.0 inches
Slab Width
69.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From IG message: “Rode the banana today.. lots of fast moving sluff. Had a mid elevation pocket pop. New snow seemed to have bonded well, the spot that did pop had formed into 12” slab below rock face.”

Bridger Range, 2024-04-08

From IG message: “Rode the banana today.. lots of fast moving sluff. Had a mid elevation pocket pop. New snow seemed to have bonded well, the spot that did pop had formed into 12” slab below rock face.”

Bridger Range, 2024-04-08

Skier triggered avalanche in Banana couloir

Date
Activity
Skiing

From IG message: “Rode the banana today.. lots of fast moving sluff. Had a mid elevation pocket pop. New snow seemed to have bonded well, the spot that did pop had formed into 12” slab below rock face. Little to no signs of instability.”

Region
Bridger Range
Location (from list)
Ross Peak

Skier Triggered Storm Snow Avalanche, N. Bridgers

Flathead Pass
Bridger Range
Code
SS-ASu-R2-D2
Elevation
8200
Aspect
N
Latitude
45.94830
Longitude
-110.99000
Notes

From obs : "After skiing two laps on East facing terrain two basins north of Anger Lake basin and seeing no significant signs of instability, we descended into a north facing gully around 8,200ft and triggered an avalanche on the new snow/old crust interface. The crown was 4-18 inches deep and propagated the entire width of the gully ~40 feet and ran the entire length of the gully ~500 vertical feet. I was able to ski out of the avalanche right as it broke and was not carried. "

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year