Snow Observations List

From FB Messenger: "Major fractures and shooting cracks across whole hillsides today. Dry Fork. Targhee Pass."

While riding today on Lionhead we saw several natural releases on steeper terrain Mainly on Targhee Peak. On all aspects of slopes we experienced large cracks and collapses that would extended 75 plus yards ahead of our sled. We did not venture into steeper slopes but it sure felt like they would slide easily if we did! 

Ski toured south of Cooke City today to try and take stock of the recent natural avalanche cycle.

Avalanches were observed on all aspects, except south.  A few photos attached.

Of note, many crowns have quickly disappeared, with additional wind loading.  Particularly from recent N, NW winds.

Still getting widespread collapsing and cracking, particularly above about 9300'.  

One collapse, in relatively wind sheltered terrain, photo attached, was wild in that the cracks shot away from me about 100' relatively slowly, and then circled back in a big loop!  About a 3 second symphony of movement in the snow.  

Higher in more wind exposed terrain, the collapses became spooky, with Pencil hard wind slab in places.  There the collapsing was much louder- and communicated the large mass of snow above that weak layer.  A couple of times they made me jump, and I am typically quite comfortable with whumpfing when I am in safe terrain.  It's just humbling when you feel the energy of a very large mass of snow move.

Good to give those hard wind slabs an extra wide margin though, because I've once seen a section of flat ridgeline avalanche into a connected steep slope (deep slab/ hard slab in the Wasatch, 20yrs ago).

We toured into Beehive and Bear Basins on the final day of the Arctic deep freeze. No forth coming signs of widespread instability, but we found unstable results in our snowpit on the SW facing slope to the south of Tyler's (ECTP18). The slab failed and propagated on depth hoar near the bottom of the snowpack. North of Spanky's in Bear Basin, there was plenty of weak snow but insufficient slab to propagate failure in tests (ECTX and PST 30/100 Slab Fracture). 

The weak snow making up the foundation is nearly universal, but the snowpack is not universally unstable. Where these weak layers are capped by a sufficient slab of cohesive snow from wind-loaded drifts or recent storms, they can produce avalanches. Avoid the avalanches by seeking out lower-angle terrain or minimize the odds of triggering a slide by selecting terrain sheltered from recent wind loading and testing for instability before considering steeper terrain.

I was cutting down a hill and this slide broke loose around 20 feet away, no one was hurt I’ll attach screenshots of where we were on maps and a picture of the minor slide. 

ECT failed at 9 at most recent layer of facets, 50cm above ground level, 15cm thick, approaching ball bearing consistency.
East facing slope, 7848’
Total snow depth 75 cm
Hard slab between 35-50cm, second facet layer at 25cm, consolidated to ground, couldn't get either the middle slab or lower facet layers to fail. 

Some cracking while we skied out.

From email: "Beehive today. HS on an east aspect at 8740' was 80 cm.  F to 4F from 85 to 55, and then a pile of facets broken up by a few thin MFCR interfaces.  Interfaces at 55, 45, and 35.  35 to 5 is 2-4 mm 4F DH, sitting on 5 cm P+ MFCR that is also faceting out. 

ECT's would initiate at one of the three interfaces, but none of the 5 propagated at all beyond the shovel width. CT13 SC @ 25 within the DH.

Super weak structure, but not a sufficient slab where we were to drive propagation.  

We crossed paths with a party in the lot at the end of the day who descended the east shots into Bear Basin.  They found a similar structure and reported no reactivity during their facet pow ski. "

From email: "Lots of hand pits to look for the SH and only found it in open areas at higher elevations. The SH was 10-15mm in size, well intact and "sturdy", overlaying small-grained facets. In hand pits, the column would fail upon isolation, yet the slab wasn't very cohesive, even in windloaded areas. The hand pits were failing on the facets underneath the SH. Some cr, co at higher elevations.

One crown on the Middle Siren, probably part of the last cycle. 

Winds were L-M out of the south and S-1 snow starting at 11am. 1cm of new by end of day. "

A small avalanche was noted in Black Bear Canyon on a northeast facing slope. Snow was wind loaded, cornices were seen on nearby slopes. This appeared to be storm slab and likely rider triggered. Slope was greater than 30 degrees. 

Observed wind slabs forming on top of weak snow. Saw cracking as well.  Snowing and blowing on the way out.  Photo taken near Texas meadows at 7800’

Dug pit in a protected area in the trees around 9250’. A layer of soft new snow (about 25cm) was sitting on top of  a base of facets. Total snow depth 1m. Thin crust around 50cm. ECT and CT broke near the new snow/facet interface. 
 

In other areas, we saw a thick layer of surface hoar buried about 15-20cm deep. Large striated depth hoar was also observed at areas with snow depth <1ft. 
 

A potential crown was observed from a distance across republic creek on the south side of the drainage.  
 

https://snowpilot.org/node/58881

From email on 01/13: "From Miller Ridge today, I had a brief look into Sheep Creek, and to the mountains south of Cooke City, and observed 7 fresh slab avalanches (that happened in the last 1-3 days).  Will send photos of them later if I can get better views.

Most of them were on NEerly aspects, and appeared to be on the new/old Jan. 5th interface.  Mid and upper elevations, most commonly in wind loaded terrain.  Some propagating a few hundred feet wide. "

From email: "Toured into Republic creek with our class. Noted two D2 soft slab avalanches. One on a west aspect and the other on an east aspect at about 9000'. I estimate the crown was 15-40cm deep and likely ran on the same layer as other recent avalanches in the area. 

ECTP4 down 25cm on SH in one pit where there was recent wind transport and a more cohesive slab. Other pits in sheltered areas produced ECTN's on the same layer. HS 100cm, 8200', W aspect. Some localized cracking and ,collapsing."

We observed widespread shooting cracks on all ridges and all NE facing slopes. Cracks would propagate up to 200’ in front. Heavily wind effected sastrugi conditions.

I observed a large whumpf in a flat meadow, around 8500'

Saw this avalanche today on the North end of Sheep from the Round Lake warming hut. Natural or possible snowmobile trigger 

Saw a natural avalanche on the east side of Henderson from the Lulu Pass Rd. Also observed a natural on the east side of Sheep Mountain. These likely happened during or near the end of the last storm on 01//10. 

From email on Jan. 12th : 

"The avalanche is on Miller Ridge, on an easterly aspect, around 9k'.  Crown appears to be about 2' deep.

I toured around on SWerly aspects, near Daisy Pass, up to 10k'.  

Widespread collapsing and cracking.  The collapsing was not especially audible, but the cracks often shot out 50-100' spectacularly- while setting an uptrack, and on descents.  

The collapsing and cracking was much more pronounced above 9600', and was happening on the new/ old snow interface.  This was somewhat surprising in this location, because the old snow surface was Very heavily tracked by snowmobiles prior to this storm cycle.

New snow:  was finding about 40cms settled on top of the Jan. 5th interface.  Slightly upside down with the wind from last night.  4F- over F.

Weather:  cold temps.  It cleared for about 45 minutes late morning, and then clouded over again.  Moderate winds from the west, but strong and blustery at times, creating temporary white outs."

GNFAC note: the avalanche on Miller was previously reported here.

Broke loose a slide just below the radio tower standing above the crown. Broke about 30 cm down on a layer of weak snow. 

Also saw very unstable snow pack at the top of the main gully below the radio tower, large cracking and settling. Snow propagated across but came to a stop before a slide began. Large chunks of snow and debris broken off from the cornice to above main gully.