23-24

Wet avalanches in Island Park

Date
Activity
Snowmobiling

From IG mesasge (4/6): "Some wet action at arange peak near Sawtell yesterday. From slope Dave and I did our first pit on Monday. Lots of release in that new old interface but didn’t see anything releasing down deeper."

Region
Island Park
Location (from list)
Arange Peak
Observer Name
Zach Bailey

Fairy Lake Obs Sunday 20240407

Date
Activity
Snowmobiling

From email: "Riding was good - deeper than anticipated, though maybe not worth the damage and mud on the way out.  

There were plenty of signs of storm snow instability, especially in the wind loaded terrain. Didn’t really need to dig to be on alert. We kept the angles relatively low all day, plenty of fun pow to ride in the trees. " 

Riders also noted a human-triggered avalanche on the shoulder of Hollywood Bowl

Region
Bridger Range
Location (from list)
Fairy Lake

New Snow Avalanches in the Bridgers

Date
Activity
Skiing

We toured up the Ramp today from the Bradley's Meadow backcountry gate. Near Bradley's we measured 19" of snow and 2.7" of snow water equivalent. On several test slopes, we observed cracking and only triggered small sloughs in steep pockets of terrain. At noon we stopped above the refrigerator chutes and dug there. We found 24" on new snow with 3.05" of snow-water equivalent. In the storm snow, we had ECTP6, ECTN11 & PST24/100 SF. Below the recent storm snow was a 1.5" thick crust with moist snow beneath. 

Near the top of the Ramp we saw a small skier-triggered avalanche that buried a portion of the skin track in front of us. While skiing down the ramp new snow was easily sloughed but never picked up much momentum. On our second lap, we saw several skier-triggered storm slab avalanches breaking ~1' deep within the new snow (R2/D1.5). We saw one larger avalanche below the cliffs between the Refrigerator Chutes and Wolverine Cirque (R2/D2). We spoke to a skier who skied Wolverine Crique who reported many small storm slab or slough avalanches. All of these avalanches occurred on slopes steeper than 35 degrees. 

Snow continued in strong pulses throughout the day and we estimated 2-3" fell between 12:00 and 2:30 pm. At the top of the ridge, winds were light from the south. At the middle and lower elevations, winds were moderate with strong gusts. Bradley's Meadow back to the parking lot was very wind-affected. 

Region
Bridger Range
Location (from list)
The Ramp
Observer Name
Zach Peterson

Small, Skier-triggered avalanche at the Throne

The Throne
Bridger Range
Code
SS-AS-R1-D1-S
Aspect
NE
Latitude
45.88220
Longitude
-110.95200
Notes

A skier triggered a small avalanche on a steep north-facing pitch, but it did not run far. We saw limited cracking on a layer within the new snow generally 4" to 1 foot deep, and got an ECTP11 on this layer in one of our pits on the east-facing pitch near the standard ski track. Our other pits, one lower on the east face and to the north of the saddle at the top of the Throne, resulted in ECTNs between 5 and 15 on this layer within the new snow.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
R size
1
D size
1
Bed Surface
S - Avalanche released within new snow
Slab Thickness
12.0 inches
Vertical Fall
50ft
Slab Width
25.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Mt Ellis Observation

Date
Activity
Skiing

Roughly 2 inches of new snow in the parking lot at Bear Canyon.  Up high on the top of Mt Ellis at 8300 feet there was 6 to 8 inches.  Did a column test and it broke on the new snow layer above the crust about 23 cm down from the top at 3 taps from the elbow.  Then we kept going and got it to fail at the weak layer near the bottom of the snowpack at 6 taps from the shoulder.

Region
Northern Gallatin
Location (from list)
Mt Ellis
Observer Name
Jake Hacker

Storm Snow Instability

Date
Activity
Skiing

We traveled into the Throne on a snow-covered road, but unfortunately, by the time we came out at the end of the day, it was a couple of miles of off-and-on mud. I can't really see how the road will last beyond the end of the snowstorm for snowmobiling. By the time we turned off the road for the final ascent to the sled boundary, there was a foot of new snow, and by the top of the Throne, over two feet of new snow equal to 2.5" SWE. 

There was a thick, supportable crust below the new snow, and our primary concern was instability within the new snow and on wind-loaded slopes. A skier triggered a small avalanche on a steep north-facing pitch, but it did not run far. We saw limited cracking on a layer within the new snow generally 4" to 1 foot deep, and got an ECTP11 on this layer in one of our pits on the east-facing pitch near the standard ski track. Our other pits, one lower on the east face and to the north of the saddle at the top of the Throne, resulted in ECTNs between 5 and 15 on this layer within the new snow. While there was some limited wind transport of the new snow, we did not find any slopes that I would define as wind-loaded to test instability. My educated assumption is that you could trigger a large avalanche on a wind-loaded slope right now. 

While we traveled in and skied avalanche terrain, we stuck to the lower-angle end of the spectrum and selected simple slopes with fewer terrain traps. 

The new snow will provide fresh ammunition for wet, loose avalanches as the temperatures warm this week. 

Region
Bridger Range
Location (from list)
The Throne
Observer Name
Dave Zinn