Snow Observations List

We rode to Ski Hill and dug 10-20 feet north of where it looked like an avalanche class had dug earlier this month. East aspect, 8,500'. Snow depth was 65-75 cm and we had an ECTP30 on the weakest, soft facets 20-30cm off the ground. Poor structure. We suspect this slope had been collapsed at least once from previous groups. Surface hoar was buried below the recent 6" of snow and was not reactive in tests, but pretty easy to see in the pit wall with large 1-2cm crystals above near surface facets.

We rode further up the ridge to "Marge" and dug on an east-northeast aspect. HS was 70-85cm and we had ECTP14 on weak depth hoar/facets 30cm off the ground. Also similar findings of non-reactive surface hoar below 6-7" of recent snow. Interestingly, we also easily found surface hoar in hand pits on more wind-loaded/exposed parts of the ridge and it seemed to break more easily here. This is noteworthy because wind-loaded slopes with buried surface hoar can be a deadly combination.

Calm and sunny today with some recent drifting of the new snow, but plenty of snow to be drifted into wind slabs still.

Toured into the southern Lionhead today. Yesterday’s warm weather made the snowpack more moist, and the upper snowpack was much more cohesive than in days past. Snow was glopping on skis and skins up to around 9k. I got on NE, E, and SE aspects, which were quite reactive, with more wumphs than in the last few days.

Went on a ski tour up Lionhead Ridge yesterday (12/18). Noted lots of sled tracks high-marking avalanche terrain on the east side of the ridge, but no major crowns. Saw one small natural crown on a NE rocky outcropping around 8k, 1 foot deep and isolated. Felt a lot less collapsing than last weekend, however still found some instabilities. Notably a remote collapse that propagated around 50’ in length at around 8200’ on a NE aspect. 

Skier triggered avalanche at Lionhead on NNE, 8600 ft. Video of remote triggering slide on IG

Widespread wumfing between 7,000 - 8,700ft. in Targhee Creek. (12/15)

No natural slides observed.

Crazy large surface hoar also observed on open, southerly clearings, measured 1+ cm. Very rotten snowpack otherwise.

We rode up Denny Creek towards Watkins Creek and spent the day below the ridge where we saw two natural avalanches. These avalanches broke 12-18" deep on weak faceted snow above a stiff crust. The first avalanche presumably happened sometime near the end of the last storm cycle (12/11), as it had a few inches of snow on the debris. The second was more recent, in the last 24-36 hours. Both were at 8500' and were on NE and E-facing slopes. 

We dug two snow pits near these avalanches and saw propagation in both on a layer of weak sugary snow buried about a foot deep (ECTP13 & ECTP12). Across the area surface hoar was easy to find on the snow surface. 

From email: 12/13: "Many slopes had half-inch to inch-sized surface hoar crystals on the surface, some of the largest I've ever seen! 

Wind was light out of the north on the ridgeline. We noticed 2 natural avalanches on the east-facing slopes below Bald Peak. I lost count, but we experienced well over 30+ collapses while walking on the ridgeline. Many of these collapses were very large and we were able to watch the slopes 'sink' by upwards of an inch which made our hair stand on end.

We dug a pit near the saddle below Lionhead Peak at 9300' on an east-facing slope (HS ~85cm). We performed an ECT and our results indicated poor stability (ECTP 14 @ 50cm)." 

Spent the day up near ski hill with West Yellowstone Avalanche Fundamentals course. 

Our group observed a large collapse below ski hill.

We dug various pits @ 8000' below ski hill and found HS 85-55cm on NW-NE aspects.

The snowpack structure there had weak snow at the ground capped by a stout ice crust with faceted snow over the crust beneath the recent snow.

We recorded ECTP4, ECTP11, ECT20 & a few more propagating results on facets above the crust. 

There was widespread intact surface hoar. 

From email: "I dug a pit in the normal location to check the snow pack conditions and here’s what I found.
Aspect: East
Slope Angle: 19
Elevation: 8100ft
Total pit depth 70cm
Winds: light 5mph with gusts up to approximately 15mph. I wasn’t on the very top of the ridge so I was a little protected.
ECTP 22 The failure was right at the old snow and new snow line 27cm up from the ground.

The snow coverage of the parking lot, trail up and off trail areas wasn’t great, but I’ve seen worse."

The snowpack at low elevations is thin (<1 foot). Off-trail riding looked questionable, and we let the sleds stay in one piece for another day or two. We went a  cornice line at 9000.’ We walked over to our pit site on a NE facing slope, triggered a large collapse, and got an ECTP13 in a snowpack that resembled what Dave saw at Lionhead and Ian and Alex saw in Cooke City. There was 8” of new snow with 1” of SWE with a total snow height of just over 105cm.

Across the way, we dug on a SW-facing slope and found a similar snowpack structure although there were a few more ice crusts mixed into the 90cm deep snowpack (ECTP14).

We rode up a bit farther to get a view of the Jefferson Bowl and saw one, small natural avalanche that occurred within the storm snow.

There was no real way to navigate avalanche terrain without rolling the dice with the persistent weak layer that makes up the foundation of the snowpack. Avoidance is key.

From IG: “Skied in the lions head today on a northeast slope at 8,300 feet. Clear wind loading and reactive cornices, however storm snow was low energy with little movement. 10-14 inches of medium density snow. Whumpfing was noticed on all slopes on the eastern half of the compass.”

Was splitboarding up near lions head ridge today. Made some bad decisions and kicked off a good slide in a NE facing chute. Was with 2 buddies, 1 of which skied the line 3 weeks ago.  Underneath about a foot of new powder snow there was a firm crust that seemed like it was old  hard windslab in the gut of the chute, and I think a sun crust on the riders left side(East aspect). We had 2 spots where we were planning to re group at, first was a small cubby area right before a slight rollover about 75 ft from the top. I dropped first, made some turns down toward the pulloff, as I pulled in, I triggered a good size slab that propagated maybe 40-50 ft across, at the rollover as I carved into the pulloff.  Pulled  all snow  out of the chute down to the ground. Seemed to have failed on sugary facets on ground/ice crust close to the ground... 

We rode to Ski Hill and dug on a NE aspect at 8000'. The HS was 40 cm with the top 15 cm being from yesterday's storm. This soft new snow was sitting on a thick supportable crust, and below that crust was weak-faceted snow. Stability tests showed no results, ECTX. From here we transitioned to skis and began walking towards the Lionhead Ridge. As we increased in elevation the amount of new snow increased and we experienced small whumpfs and cracking as we approached the ridge. Below the ridge, we dug on a NE aspect at 8700'. The HS was 56 cm and there was 22 cm of new and wind-drifted snow on top of similar layering. We got an ECTP1 at the interface between the new snow and weak snow just above the crust. We saw no recent avalanche activity but another party reported seeing a small avalanche further along the ridge.