Snow Observations List

From IG: Wet slide to the ground above Quake Lake. 

On sunday 4/14 a large wet loose avalanche ran naturally in closed terrain at Bridger. The larger of the two in the photo is from 4/14 at 1230pm. The other slide, on the left, happened yesterday or late in the day Friday.

Saw what looked like a wet slab avalanche from the road along the Madison River.  Roughly north facing slope at 7500'.

Saw a slab avalanche on a NE face at around 9000-10000 feet. Did not see any signs of instability on the tour, but there was not a very concrete freeze. Everything below 8000 remained unfrozen. 

This afternoon I drove up Bridger canyon to Seitz Rd to see the extent of wet snow activity, and stopped in a few places to look with binoculars. There were many loose wet avalanches that ran over the last 1-3 days. I estimate they involved the upper 6-12" of snow. Activity was widespread and many slides were plenty large enough to be dangerous, but there was nothing especially remarkable about the size and I saw zero wet slabs.

Temperature was 65-70 degrees in the canyon, mostly clear skies with a few clouds, calm to light wind.

Natural cornice failure and small slab on Iceberg Peak’s NE face. We skied by the day prior and judging by what the wind did to our tracks overnight, this looked like it happened in the morning.

Rode from Buttermilk to Lionhead Ridge to take down the weather station for the season. The snowpack was fully saturated and sloppy at lower elevations. By 8000 ft there was a firm crust with a couple inches of wet snow above it around noon. Winds were breezy at ridgetops, keeping the snowpack a bit cooler (but still getting wet). Ominous clouds moved in around 12:30 pm. We quickly left before getting rained on. 

We saw no signs of recent avalanches.

Rode up cottonwood creek on the west side of the crazies. Saw several recent wet loose slides on southern aspects as well as some isolated slides on north/west aspects. Only saw one larger slide that had a wide crown(500ft) D2 on an east aspect.  All slides were breaking in the upper 40cm in new/old snow.

Dug a pit north east aspect HS270cm ECTN24 @40cm down from surface. Melt freeze down 70cm might start reacting when water penetrates through upper snow pack, dry snow in upper 60cm but becoming more moist on solars.

Driving home from Bridger Bowl I spotted a number of wet loose avalanches in Argentina bowl. It was 1:30 PM when I saw them and the sun was still blazing. I would expect there was more activity as the afternoon progressed.

Unintentionally triggered a large cornice collapse on the south face of the Sphinx.  I should have expected it, but it was certainly touchier than I was anticipating. Intermittent wind gusts kept upper elevations cooler and we found somewhat cold snow up high. At treeline and below it was hot and crusty! Photos show cornice before and after. 

From email: "Had propagation on 1.5mm rounding facets below the mid-March, 1/2cm thick and knife hard MF crust. This location is always shallow and has a poor structure, but I was surprised to get propagation.

Further up valley on a west aspect, HS 130, 1 of 2 pits had ECTP28 on the basal facets. Pretty wild to still be getting propagation in mid April. 

Winds were light out of the south, gusting to strong at ridgetops out of the west with active snow transport. No wet loose activity seen today, but several old wet loose avalanches on Climax from the last warm up. "

We skied two North-facing lines in the Northern Gallatin range on Wednesday ranging in elevation from 8500 - 9700 ft with some slight West and East flavor. We saw no signs of instability and set off a couple large sluffs in the top 8-12" of snow and some wind-loaded pockets breaking 6-8" deep. I dug a pit and did a CT and ECT and got CT15 on new snow 30cm deep and CT28 on a layer 45 cm deep. Got ECTN16 on same 30-35 cm deep new snow layer. The interface with the old freeze-thaw layer below the new snow did not show a very high quality fracture plane / bed surface for the upper new snow to slide on. the freeze-thaw layer was about 1-2cm thick but did not feel it while skiing. Upon pulling on ECT column with shovel, broke on 45-cm layer with poor quality and also on basal facet layer at ground. Overall right-side-up snowpack density going from fist to pencil hardness pretty linearly. Total depth of snow 210cm. Depth of new snow from last storm approx. 12-16". 9600 ft NNE aspect. 

Dug a pit on our way up the west side of Henderson Mountain. Incline 26 degrees, elevation 9545. Surface depth at 165cm, dug down to about 65cm. Performed extended column test and yielded ECTN17 along melt freeze crust at 135cm above ground. 

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. 

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.”

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

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. 

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.

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. 

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.