Snow Observations List

From email: "Snowpit from this morning:  SE aspect, 9250'.  

It snowed all day in Cooke (S2), mild temps, light westerly winds." 

Today, we skied near the wilderness boundary north of Round Lake. On a wind-loaded test slope at the top of our second ski run, we were able to get recent drifts to crack, but not avalanche. Slightly further down on a steep roll the second skier in our group triggered a small wind slab avalanche. This avalanche was 15-20' wide, 8" deep, and ran for about 30-40 vertical feet. The skier easily skied away from the slide and was not caught. 

Winds remained mostly calm but increased by the end of the day. Snowfall through the day was enough to partially cover our morning tracks and we found 2" of snow on our snowmobiles at the end of the day. 

skiing north of cooke city today observed this Small windslab on a South facing slope ~9800 ft.
 

Today, we rode north of Cooke City through Abundance Basin around Scotch Bonnet ending at the East Henderson bench. We found anywhere from 4-12" of new snow that fell in the last 24-48 hours. Strong winds have transported this new snow into thick drifts even in more sheltered terrain. We did not see any recent notable avalanches but saw many crowns and debris piles from two weeks ago. 
On the East Henderson bench, we dug a snowpit and found 235cm (almost 8') of snow. We found moist faceted snow 6' below the surface near the bottom of the snowpack. At the top of our snowpit was 12" of new snow above a stiff crust. Our stability test showed ECTN15 results on this interface. 

Snow continued off and on through the day with little to no accumulation. Many slopes had signs of either wind-loading or had been scoured by recent wind resulting in thinner areas. 

We toured up the Ramp. There was 6" of heavy new snow. The wind was transporting significant amounts of the recent snow at high elevations. The wind-loads weren't occurring on the ramp and lower elevation ridge terrain in a significant way. On our drive home we saw, what I assume were, natural wind-slab avalanches on Quarter Saddle (looked like a cornice collapse) and in Argentina Bowl. Bridger Peak was obscured by heavy wind-loading. There was a small wind-slab release out of Gibbs (I think), I suspect skier triggered, but I could make out a track.

On the Ramp, we observed several isolated drifts that would crack under the weight of skis. The snow was staying fairly cool and dry, but on a rollover, I pushed a small wet loose pocket downhill. Watch out when the sun and temps blast the recent snow! It is sitting on a firm crust and I expect things to get active.

We dug a pit to the south of the Ramp proper. The basal weak layers were the least weak I have seen all year. The snowpack was most from 80 cm to the ground and the facets and depth hoar are rounding. We are not out the woods, but things are improving. ECTN 20 on near-surface facets 30 cm from the top.  

From IG: Very touchy on Hollywood wall this morning. All slopes easily propagated 4-6” deep on a firm bed surface. Most were less than 50’ wide with the exception of the slide in the couloir which propagated down the entire couloir, maybe 500’ wide, and ran through the exits into the main bowl.

Today there were strong winds loading snow onto the Northeast face off of Pine Martin Ridge, just North of Ram Pasture. When we got a better view of the slope, we noticed there had been a natural wind-slab avalanche (left), possibly triggered by a cornice fall. While transitioning, we saw a small part of the same cornice break off and trigger a similar wind slab avalanche (right). 

Triggered this small windslab while skinning near a steeprollover at the top of an East facing slope above Zimmer Creek. Crown was ~20 ft wide and ran a similar distance. 2"-10" at the deepest. 

Saw small avalanches on almost every wind loaded slope out of fairy lake. The one we spotted in the pomp twins had a defined crown roughly 100ft across. 

We toured over south Bacon Rind and into Ernie Miller Ridge today. The weather was variable, alternating between periods of calm winds and warm sun, and periods of heavy cloud cover, snow, and high winds. At the summit winds were strong out of the SW, but previous wind deposits further down pointed towards recent Northerly winds. These were strong enough to scour snow off the crust, and create drifts up to a foot deep. The sun was also affecting the snow surface, rapidly warming and wetting the snow above the crust. This wet snow was not bonding well to the crust. Some cold snow remained and made for good skiing.

We took the variability of the snowpack and the risks of a consequential slide into account and traveled through moderate terrain, avoiding excessive exposure.

We rode into the weather station, across to the Wilderness Boundary, along the ridgeline to the Beaver Slide, and back. We saw one new wind-slab avalanche in Sunlight Basin. It was small. From a distance, it appeared to be about 6" deep and 30' across (R1-D1). The other notable avalanche activity was a full-depth wet slab avalanche that broke last week during the warm-up on Lightning Ridge. 

We dug a 150 cm deep pit at the Wilderness Boundary. The basal facets and depth hoar were moist. The upper-level melt-freeze crusts were so thick and hard that even with a saw assist, we could not isolate the column to the ground. There were two newish near-surface facet layers in the upper 10" of the snowpack. No hazard now, but they will be something to watch when loaded. 

Skied into Frazier basin today. Triggered a few small windslabs and saw a lot of cracking on NW aspects. All windslabs were still small breaking a few inches deep 10-15 feet wide and only running short distances in steep terrain. Winds were strong from the NE all morning and still blowing hard and continuing to load slopes when we left at 12:30. 

Spent the last few days traveling around the Cooke City Area.  New to the area so this is just some general notes/obs of things we saw that seemed interesting:

• weak basal facets/depth hoar widespread across all aspects and elevations travelled
• no cracking or collapsing noted 
• anywhere from 1-5" of new snow in the last few days. Surface conditions quite a mixed bag and tricky to predict what would be crusted or not I think due to how the sun has popped out at random times and locations in between snow squalls. 
• pits were dug in 2 locations (see images) -
  • S aspect on Henderson, many clean CT (Q1/SC) results and ECTP results on both a mid pack facets and basal depth hoar, even though depth hoar was wet (could make a snowball). These test results were repeatable in 2 pits dug nearby each other in same location representing both shallow (~160cm) and deep (~200cm) spots. Video of this pit linked. 
  • W Aspect Republic Crk/Woody Ridge - same basal facets/depth hoar noted, but not reactive to ECT (ECTX result), even when top half of snowpack was removed.  This is near the collapse ob from another party the other day so points to the spatial variability - no result in our pit but a reactive collapse nearby from another party noted. 
• Widespread crowns visible from previous cycle almost everywhere you could imagine, especially on easterly aspects. Don't think we saw anything that hadn't been reported, but must have been a very impressive cycle. One photo attached is of a shallow SE aspect slide seen in Pilot Crk drainage. I thought interesting because of how shallow the snowpack seemed there. 

The snow rangers rode around Battle Ridge, the Throne, and Naya Nuki today.  New snow depth ranged from 2" to maybe 4-5" in sheltered/lee locations.  Lots of older wet slide debris was visible but no avalanche activity in the new snow.  There is a very firm crust in most areas and anything with southern exposure has gotten very thin, including the trail in.  We rode through several large mud patches on the way out.  

Today I released a windslab with a ski cut on town hill. 6-10” deep and approximately 30’ wide. It ran about 40 vertical feet. 

From IG Message: ECTP20 on a NE facing slope on Ross Peak at 8700' elevation.

Toured out to the playground Sunday. 2-3" new snow provided good riding on smooth surfaces. HS around 1.5-2M at 8-8500' on North side of compass. Did not plan to dig but after observing a significant deep slab from afar that propagated into shallow angled terrain AND took out ski tracks, I found myself with a hypothesis I could not ignore: Have we transitioned to a wet spring snowpack? I assumed this was a wet slab but needed more information. In fact at this location the snowpack was still dry and we still got stubborn propagation at the basal facets (ECTP25). Very difficult to estimate timing of incident however it stands to reason that loose wet snow came down from above and pulled out this slab; most likely caused by rapid warming and a poor refreeze sometime last week. While not a far running avalanche, it did take out the whole snowpack and deposited 10-15' of debris in the trees. We classified it as HS-N-D2-R2-G

Final thoughts: I have not skied in SW MT much this winter but a few things stood out to me yesterday. Thin, shallow snow equals weak snow. Most slabs are hovering right around the 1M mark, just enough for a human to trigger. Recent activity has pulled out many shallow slopes that I have often wondered over the past decade, "can this avalanche?" This winter has provided me many good images of "sneaker" slopes that are just steep enough to run. Despite the allure of untracked snow, seeing propagation at the ground in late winter has my hackles up and I will be staying out of avalanche terrain (sigh) for the foreseeable future. My suggestion: Go to the Tetons where there is 100" sitting on the deck or stay out of avalanche terrain for now. 

Note from GNFAC: This avalanche happened on 03/20/2024: details here.

Skied in Frazier and fairy lake area today. No signs of instability or wind loading on the north facing slopes we skied. We found a very firm crust layer under a few inches of new snow. The new snow was sluffing quite easily but wasn’t consolidated. It was lightly snowing all day but no wind to speak of moving the new snow around. 

We rode up Buck Ridge towards the Bear Creek Wilderness boundary, along the way we found 6 to 10 inches of new snow that fell over the last 24 hours. In many areas this new snow has formed large drifts even in treed areas. Behind McAtee Basin, we saw a small natural wind slab avalanche on an east facing slope, and we saw a natural wind slab in Bear Creek. From a nearby ridge line we could see snow being transported at ridge tops. On a small test slope near Muddy Creek we intentionally triggered several small avalanches in wind loaded terrain. In First Yellow Mule we dug a snow pit on a north facing slope, at 9,300’. We saw ECTN 13 and 14 scores below the new snow.

Strong north wind prevailed through most of the day at or near ridge lines. We saw lots of evidence of both cross loading and wind loading on many slopes.