Snow Observations List

I skied above Hebgen Lake today, and found excellent surface conditions with poor stability. A pit on an east-facing slope at 8650’ had a clear line visible where the buried surface hoar is, and an extended column test yielded ECTN2 10 cm down on the interface between older snow and the new snow from the past couple days, and ECTP7 on the buried surface hoar. This layer is very well preserved. We did not experience any collapsing or cracking and saw no natural slides, but another group triggered two small slides on a he surface hoar while traversing a ridgeline at the top. 

Ski cut sent a slide that failed on the known-to-be-reactive buried surface hoar layer . Avalanche broke around 12-14” deep, 100’ wide and ran around 100 yards. It was extremely sensitive.
We had skied a similar angle/aspect slope earlier and didn’t get any reactivity. Occurred around 9000’ on NW slope.~ 32 degrees. We did this 2 times on what we thought to be low angle slopes. ended up skiing down a low angle ridge line. The buried hoar isn’t everywhere but it’s touchy when found. 

We toured up to the Mt. Blackmore ridgeline today. Near Mt. Blackmore most of the snow was wind affected, and today’s winds at the ridgetops were not blowing snow around because there is little snow left for the wind to transport. We dug three pits on different aspects and elevation bands, and we didn’t find surface hoar in any of these pits.The pits we dug had facets near the surface all the way to the bottom of the snowpack, and it was capped with a 1-3” of wind-packed snow. We were able to get an ECTP18 on facets above a crust 10” below the surface on a SE aspect at 9,500’. And, we got an ECTP18 on a NE aspect at 9,800’ in a shallow, wind stripped area below Mt. Blackmore’s ridgeline. This was in a layer of facets 2 feet below the surface. We were not able to replicate these results in either snowpit. Buried weak layers are getting harder to trigger, and these pits showed how finding a thin spot on a slope could still trigger an avalanche.

We observed a north-facing natural sluff turn into a reasonable slide release over the cliff bands from the ridge line between Miller and Wolverine today while skinning on the flat bench above the road out to Wolverine Peak today. I think it released right at Sunset peak. It may have started with a cornice release but was more like wind loading on the steep face. We also saw some minor cracking on north facing wind loaded roll overs above the bench. We opted to descend low-angle trees back to our sled and to go ski Henderson.

Our goal was to ride the North Face of Mount Blackmore yesterday in hopes of north aspects still holding good snow. We noticed some cornices on the top of the line and changed our objective to another entrance onto the north face farther down the ridge from the main North face line. When we got to the top of the line we could see it was noticeably wind loaded at the top and we found very large depth hoar crystals near the bottom of the snowpack. Heaving wind loading and the large depth hoar crystals gave us pause and we hiked back up and skied down the East face. We also saw what looks like a cornice about to break off along the ridge of the North face. 

From IG:
“Snowpack observation from 1/14/23

Northern Bridgers-Frazer Basin

Chute skiers left from the exit chute/sled access boundary on ridge. 
Skied a more wind protected N facing chute and experienced stability skiing. Did 2 ski cuts before entering as well as doing a shovel shear on the top ~2ft of snowpack. No clean shear for the test or other observations of instability. As a result we skied. 
Decided to start skiing up another, more open face to the E and stopped to dig about 1/3 of the way up once it started to get a little steeper. Dug on a Due N slope at 8430 ft. Snow depth was 205 cm from base. Column test failed at CT11 and CT15 at 175 and 135cm from base respectively. Was a clean break. Conducted an ECT which went at ECTP12 and 14 at the same depths. We skinned off the aspect and skied conservative lines the rest of the day.”

We rode in 1st, 2nd, and 3rd Yellowmules into the head of Muddy Creek today. At the 1st Yellowmule we found punchy, weak snow in several places. This is a sign that the snowpack is continuing to facet near the ground. The snow seemed more faceted than it was the last time we were in Buck. We saw a new layer of surface hoar on the snow surface all over Buck Ridge, which could be a problem in the future. We also found a layer of buried surface hoar 8-12” below the surface throughout Buck. 

We dug at the head of Muddy Creek, and we found 160 cm (~5 feet) of snow on a north aspect. We got an ECTP8 on a surface hoar layer 10” below the snow surface. Where we dug was near a ridgeline, and the surface hoar was intact despite this area getting wind. When deciding to get into steeper terrain riders and skiers should assess for instability with an ECT at this layer, and they should still be wary of the weak, sugary snow at the bottom of the snowpack.

Started a small wind slab avalanche on an isolated rollover about 2/3 of the way down the face of elephant mountain yesterday (Thursday January 12th). Broke a few inches deep, about 8 feet wide, and ran less then 100 ft. 

Today my partner and I set out to ski Divide Peak and then re-ascend to connect the ridge over to 'Fat Maid' in Maid of the Mist basin. On our way up Divide peak, a hasty pit yielded poor results so we decided to bail on the main SE Gully that leaves from the summit. We still skied down from the shoulder, in the trees, and continued on our plan to head back up and over to Maid.

While skiing down 'Fat Maid' I triggered a shallow wind slab, after I was about 3/4ths of the way down the couloir. The slide broke to my left as I entered a wider section of the run, that holds a small perched bowl feature (which is what ripped out). The slide didn't propagate out into the main couloir, so the debris never impacted me. Even if it had, I don't think it would've been big enough to knock myself or any other skier off their feet. The slide was about 1/2 the width of the couloir and ran out to about 3/4ths of the apron's length (R2 D1?). The crown was 1-3" deep and maybe 30-40' wide. Had the wind slab been larger, or impacted one of the thin faceted layers mid-pack (like the one that scared us off Divide Peak) it could've been a different story. Thought it'd be good for people to consider heading into the weekend and unsettled weather. The picture is kinda hard to see so I did quickly draw the crown on the same image, but will send you the original as well. 

On another note, we found an impressive amount of surface hoar, widespread, even in alpine areas exposed to sun and wind. Hopefully it get knocked down before the next storm! 

side hilled off of two top trail and broke small slab off

We rode to ski hill first, and we dug a pit on the NE aspect near the top of the slide path. The HS was 160 cm (5 feet). We found buried surface hoar under the 10-12” of new snow, and we got an ECTN13 on this layer. Next we rode to the old weather station, and the HS was 5.5’. We found the surface hoar in this pit too, but it did not propagate during our ECT. Despite these two results, skiers near Hebgen Lake found the surface hoar layer, and they had an ECTP3 and 6 on that layer. They also noted an ECTP26 on depth hoar near the bottom of the snowpack. Although the surface hoar isn’t propagating on every slope in the Lionhead Range, it is possible for it to propagate on other slopes in the range. With this buried surface hoar and facets near the ground riders and skiers should continue to carefully assess the snowpack before stepping out into steeper terrain.

Observed widespread surface hoar growth (up to 2mm) along the Bradley Meadows uptrack. E-SE from 7400-7800’.

Today on a west aspect around 7,835' in the Bridgers, near the top of Texas Meadows my party had test results of  CT28 (SC) and ECTP25 both at 20 centimeters up from the ground. Snow pits my party dug on other aspects in the area had unremarkable results.

Starting at Bear Basin trailhead toured into Middle Basin topping out at the highpoint on the ridge.  We saw no signs of snow instability throughout the day.  The temperatures were warmer than expected in the morning, the afternoon brought cooler temps and a little snow.  The skiing was suprisingly good in places and wind affected in others.

Today we had a question that needed answering: What is the distribution of the surface hoar? We dug in 5 places on different aspects and elevations and the answer was, “Everywhere.” But the SH is small and you can’t see it in the pit wall. It is buried about 20-35 cm deep. It will need more weight on it to get it to go. If a person was not looking for it it would be hard to find without an ECTP or Q1 fracture. I’m worried about areas with a slightly beefier slab, like what we found in Henderson Bench yesterday. Propagation and human triggering seems possible in these spots, but they are few in number. We found some thin spots and felt the sled bog down in the facets, which is issue #2. Triggering avalanches from thinner areas is still on our radar and may be for most of the winter.

From Facebook: High Mountain Adventures snowmobile rental reported one of their renters triggered a slide on the waterfalls (Mt Jefferson/Sawtelle).

Photo attached of a fresh natural avalanche, just south of Cooke City today.  It appears to have run last night or this morning.  (photographed at noon)

we skied up to 9230 on a south slope of Miller Ridge in sheep creek basin.  Intermittent clouds and sun, no wind.  Much wind affected snow, cross loading.  2-4 inches of fresh snow.    HS at 9000 was 100-110cm.  Started finding wind slab on rotten base at about 8900 then at 9200 where slope steepened we observed 3-5 foot shooting cracks and turned around.  Slope was 27-35.  Had climbed thru whitebark regrowth from 88 fire.  

We had good visibility and rode to Lulu to look at an ava that was triggered yesterday, a small cornice collapse. The one on Chimney Rock (triggered 2 days ago) was not big, but more indicative of weak layers at the ground. Chimney was 2 slides side-by-side, mid-slope, that likely went at the same time. These likely broke on facets near the ground. The snowpack was thin there. We then rode to Wolverine and Abundance. We saw a new snow slide on Wolverine in the deep cleft on the face. We dug on the shoulder of Abundance (HS 200+) and did not get anything remarkable in our stability test.  We then rode to Henderson Bench. There was one small slide off the Henderson ridge by the radio hut. We dug off the bench and got a surprising ECTP 11 on surface hoar buried 30 cm under. Crystals were not big (2-4mm) and you could not see it in the pit wall, but the ECT sure popped it out.