Snow Observations List

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.

Snowboarder triggered this slide on a rollover on East Republic. Reportedly ran 80' wide, 1-1.5' deep. No one was caught.

There was 4 inches of new snow in Taylor Fork, and there was wind drifting in several places. We rode to the wilderness boundary to dig a pit. We were on a south aspect at 8,800’. HS 125cm (~4 feet), ECTN5 on surface hoar under the new snow, ECTN21 on facets 1.5 feet below the surface, ECTN 28 on facets near the ground. We rode past the Otter Slide to dig on a north facing aspect, and we had an ECTP5 on buried surface hoar. There was 6” of new snow on top of the surface hoar layer that propagated. While leaving Taylor Fork this afternoon it was beginning to snow. The additional snow in the forecast will likely make this surface hoar layer more reactive now that it is buried. Additionally, the poor structure throughout Taylor Fork could make the deeper weak layers more reactive.

We exited Bridger Bowl via the ridge and dug a pit at the top of Lazy Susan near The Ramp. It was 111 cm deep and full of facets. The lower half was facets, and the top was faceting, and there was surface hoar. We had ECTN17 and 18 at 79cm. Felt weak, but generally stable. You could trigger an avalanche somewhere, but danger is decreasing without new snow and wind-loading.

Snowmobiled to 8200ft then skied up to 9000ft. Dug a snow profile to ground on NE aspect at 8800ft. Height of Snow was 120cm (4 feet). Multiple weak layers in the snowpack including one about a foot down and a thicker layer of faceted sugary snow in the bottom 2 feet of the snowpack near the ground. ECTN29 on a crust and small grained facets about a foot down from the surface, however that slab layer released when a shovel was put behind it with a sudden pop and very little friction, see grainy photo. Surface was faceting old powder which could be another weak layer when buried. Not very reactive in this spot at the moment likely due to lack of new snow in a while. However generally poor snowpack structure is not reassuring and will need to watch when this snowpack gets rapidly loaded by new snow or wind blown snow. 

Observed recent small wind slab avalanches under the ridgeline as well as one larger slide that broke on weak snow near the ground, likely cause by cornice fall. 

@ 7740' east south east aspect 20 deg slope we found HS 87-105cm, large grain faceted snow near the ground, ECTN 29 @ 55cm above Xmas crust. Saw multiple D1-D2 DL or unknown ( couldn't see crown) in ramp/ wolverine/ hourglass couloir. 

Skier unintentionally triggered and was caught in wind slab avalanche on the Y couloir in Sheep Creek Drainage. Skier was carried 10m before self arresting. The slide ran ~250m down and broke across the entire width of the couloir. There were no injuries and skied away. 

Yesterday we tested and skied a well-protected, NE-facing line above Blackmore Lake. There were strong winds during our approach and we observed evidence of wind loading on northern aspects. By around 2 pm, wind speed and wind loading reduced significantly. At our pit location, we observed a thin wind crust (1-2cm) that moved quite readily. This layer did not move during stability tests and did not propagate while skiing, but released readily while skiing. At the bottom layer of the snowpack, we noted that the grain size increased since our visit to the area last weekend, and the faceting in this layer was much more apparent particularly at the bottom of the layer (see photo).