Snow Observations List

Went on a "loop de doop" type of tour yesterday to see conditions around Big Sky. While skiing a north aspect off Middle Peak, we dug a pit around 10k and found a hard 6 inch wind slab on the sitting on top of a firm column, ECTP16 on this top layer and it seemed like this was an isolated problem. We skied a SW aspect from the Bear/Hellroaring ridge and found great, consolidated snow from ridge to creek. We ascended and dug a pit on a NE aspect in Bear basin and found the depth hoar that everyones been talking about, we found this about 2 feet deep and had collapse but no propagation in our stability test. We skied a SW aspect back into Middle Basin in solar affected snow, a few ski cuts cleaned out the chute and the snow ran slow, but capable of taking someone off their feet. Multiple point and release wet snow activities were observed on all similar aspects off of the ridge. 

Observation Details

Observation Date:

January 21, 2023 - January 21, 2023 

Submitted:

January 21, 2023 

Observer:

RRS - Kevin Allred 

Zone or Region:

Island Park 

Location:

Yale Creek (SSW) 

Signs of Unstable Snow

Recent Avalanches? 

 None Observed 

Cracking? 

 None Experienced 

Collapsing? 

 None Experienced 

Found a layer of near surface facets 25 cm from the surface not problematic now but with new snow coming this could become a layer of concern 

Snow Stability

Stability Rating: 

Good 

Confidence in Rating: 

 Moderate 

Stability Trend: 

Steady 

Bottom Line

The snow seems to be very stable found a MF crust 45cm / surface from a warming trend early in January. Below the MF layer a strong cohesive slab. 15cm layer of DH at ground level average grain size of 2 mm 

Advanced Information

Weather Summary

Cloud Cover:

Clear 

Temperature:

17º 

Wind:

Calm , SW 

New/Recent Snowfall:

Trace of new snow past 24 hours 

Mostly clear skies light winds out of the south west no blowing snow 

Avalanche Observations

Avalanche Observation Comments:

None Observed

Snowpack Observations

Head of Yale Creek 8470' elevation SSW aspect HS 175 CTM SC @ 20 cm below surface on a near surface FC. ECTN 

Avalanche Problems

Our primary concern is a layer of SH that is variable in distribution . This layer was not evident in our snow pit location. 

Terrain Use

Our travel plan avoid avalanche terrain over 30° We traveled to observe an avalanche fatality site from 1998. The area had heavily trafficked by snowmobile activity. We remained with our conservative travel plan at 30°

Bad quality but a D2, R3 natural in Flanders cirque. Looked like it was just the new snow, but hard to say.... on a NW aspect around 9,500 feet

We are finding impressively strong snowpack. But we also have a weak layer buried about 2 feet into the snowpack that is very worrisome. It's deep enough that when triggered will be deadly, consider consequences and know where the persistent weak layer is before exposing your group. We have been on the snow all week and find lots of powder to play in without using slopes and connected terrain that is greater than 30 degrees.

SE aspect, 7640 ft, HS 130, PWL buried SH 83, DH 45, CTHsc@83, ECTN23@45. 

This PWL is widespread, but not necessarily reactive in all areas. We did feel a collapse on this same aspect and elevation yesterday, near Sawtelle Creek so we went back to test and found some results. 

On January 19 we rode north of Cooke City to dig in a variety of locations and look for the surface hoar layer that is buried 1-2 feet deep. Over the past week, forecasters and other groups have found unstable test scores on this layer, and there was at least one rider triggered avalanche and one natural avalanche that broke on this layer 3-5 days ago. These two known avalanches were on east to northeast aspects at 9,200-9,800'.

We dug five snowpits and performed extended column tests in each on 1/19/23 (I said "four pits" in the attached video, but I forgot to count one that was 15 feet away from another). Four snowpits were on northeast to north facing slopes between 9,200-10,000', and one pit was on a southwest facing slope at 9,200'. In one pit on a NE aspect at 9,200' we had an ECTP 15 on the surface hoar 35 cm below the surface. In all other pits we had ECTN14-19 at the depth of the surface hoar, and no obvious feathery crystals were visible. The layers where the ECTNs broke appeared to be decomposing, preserved dendrites or maybe decomposing surface hoar.

There was about 6" of low density snow that slowly accumulated over the last few days. Below and within this new snow are layers of near surface facets and surface hoar that formed during clear, cold nights. These may be future weak layers. There was almost no wind the last 3-4+ days, so this snow is still available to be drifted into thick slabs when the wind increases.

We stopped on a couple west facing slopes that were heavily wind-affected, and we sunk about 3 feet to the ground when we got off our sleds. These areas of shallow snow hold very weak, sugary facets that will be a problem if loaded with heavy snowfall. 

At the moment, the general snowpack stability is improving with an extended break from heavy snow or wind-loading. I suspect there are a few lingering pockets of unstable surface hoar that could be triggered, and there is plenty of weak snow near the surface. If the wind blows snow into thick drifts, or more snow falls than expected, stability could quickly become worse.

Photos of avalanches are those previously reported on Monday on Miller (photo taken 1/18) and Henderson (taken 1/17).

We were in the Beaverhead Mountains, mainly below Italian and Scott Peaks. We found various weak layers towards the top of the snowpack in places and in other places, completely bottomless pow approx 3+' deep. The weak layer areas the top 2" was breaking and sliding right around that 30 degree mark. We used Fatmap app to plan our route to the summit and worked our way around most 25-30 degree angles. Once we pushed that 30 degree angle that top 2" would release. In this area we observed the top 2" was hard like 1F or P hard, 4-5" of Fist or 4F, then another layer of 2" of P, and facets for about 20/30" to the ground. In the wind blown areas the top was almost solid, very hard and icy. 

Not good riding, but we did it.  

Observed this cornice fall triggered slide morning of 1/19/23. It was not there the previous morning which was sunny and clear. Photo: GNFAC

I dug one pit at 8200’ NE aspect in Yale ECTX. Kevin was a little lower and around on the east side of Sawtell, he felt a big wumph. He didn’t confirm what layer, but this is probably your buried SH.

Today we toured up Storm Castle Ridge with hopes of skiing the 19th Street Couloir. On the approach we were able to trigger small (2-4") wind slabs on most lee aspects, these slides ran fast and far for their size. We dug a pit at 9200' on a North aspect and we're able to identify the surface hoar but had no results on our ECT.  With 2 spotters I dug an ECT 10m below the top of the 19th Street Couloir and got and ECTP12@ 35cm below the surface. The slab was 35cm thick, pencil hardness and failed on faceted snow; the buried surface hoar found in most other pits was not present. We bailed to the opposite side of the ridge and enjoyed some wonderful burn skiing. 

Small avalanche broke while descending to less exposed areas.  Approximately 80 yards wide, 18” deep.  Slid for approximately 90 yards from crown.

A snowboarder triggered a shallow avalanche (estimated 4-6 inches deep) on Saddle Peak in the new snow. The slide was as the snowboarder dropped off "Quarter Saddle" and a second pocket propagated above him as he traversed out of the first slide. 

Another slide was seen from the highway in Argentina Bowl. This slide appears to be a shallow soft slab that ~50 ft wide and ran ~500 vertical ft.

From IG: Some people got something to run long off the south peak. People were center punching Argentina and north saddle without consequence, but the wind slabs were generally dense enough to propagate but not so dense that they weren’t easy to trigger.

From IG: Sent attached screenshot and video.

Natural soft slab release likely in the last 36 hours. Seen from in-bounds at the Yellowstone Club. Avalanche location at 45.2116512 N 111.47811 W at the headwaters of Muddy Creek. 

Observed a point release that appeared to have stepped down. This occurred SE of the “rip curl” zone. We also noticed significant sun effect and a warming trend throughout the day. 1/17/23

Dave and Doug rode around and saw multiple natural and 1 sledder triggered slide on Lionhead. Some were thin and just involved news snow and others were deeper and broke on the buried surface hoar layer.

East aspect, 10,300.  Estimated to be about 75' wide.  Likely occurred yesterday, Jan. 17th.  

Wind loading from last storm snow. Large surface hoar formed on all aspects. Also noticed 1-2cm settlement around trees on northeast facing slopes.

We crossed Hebgen lake near the dam and skied in the trapper creek area.

About 2 inches of new snow - consistent from the lake to the ridgeline. No signs of instability or avalanches observed (we didn't see the small slides triggered on Sunday). Dug on a SE aspect at 9000 ft (just below the ridge). Found the surface hoar 1 ft down (ECTN17) and fist hardness facets at the ground. Was surprised not to get propagation (maybe not enough slab in this spot?), but stuck to our initial plan and avoiding steep slopes anyways. 

New surface hoar is growing on the snow surface at all elevations, in places feathers are up to 1 cm. 

We rode to Arange Peak and dug a pit (HS 210 cm, S facing, 8800'). We found the SH/nsf layer, but it did not propagate, It was a good 2 feet under the surface. We then rode and dug 3 more quick pits and either didn’t find the SH or had ECTN or CTN. We saw no avalanches and a rider who was near Mt. Jefferson 2 days ago also saw no activity. I am still very leery of the SH and believe it survived on a few slopes and acted accordingly, i.e. no riding steep slopes.

Noted a couple of fresh slab avalanches out there today.  Both were on northerly aspects around 9300'.  Photo of one attached.