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We experienced several collapses and had propagation in multiple ECTs performed.  HS varies between 85-105cm. Photo from 9940

Photo: BMG

Photo: BMG

Today, we toured up and out of the north boundary of Bridger Bowl: up the Ramp, into Wolverine Bowl and on top of Texas Meadows. We got eyes on a lot of terrain north of Bridger and were able to dig in six or more different locations, with up to 12 extended column tests. Generally, we found a similar snowpack here as we have seen in the rest of the Bridger range: a slab of varying depths but generally about a foot thick on top of 1-2 mm facets generally in the middle of the snowpack.

In our pits near the top of the ridge, we got unstable test results with propagation on top of the facets. But as we dropped elevation, we found that we were unable to replicate propagation, and only got ECTN scores. These pits at lower elvations looked very similar to what Ian and I found just north of this area on Thursday (Ob from the Throne). One notable pit finding was a very thin layer of surface hoar near the top of the Ramp, as noted in our snowpilot (attached). 

Pit propagation was our first sign of instability, and as we continued along ridge past Wolverine we came across a R2 D2 slide in the Hourglass chute above Wolverine. It looked to be triggered by an intentional cornice drop, was around 12 inches deep at the crown, 100' wide and ran 850' vertical feet. It looked around three days old. As we skied down into Wolverine from the Ramp, we noted two other avalanches that seemed like they broke during the loading event that occurred last Sunday/Monday (12/15-16). These slides looked similar to the natural avalanche noted on Saddle this Thursday (Saddle Peak avalanche observation). 

Throughout our tour, our snowpack layers looked very similar. Pit propagation up high and recent avalanche activity showed us that the odds of triggering an avalanche in steep, wind loaded terrain were higher than we were comfortable with riding today. At lower elevations, our findings indicated the odds of triggering an avalanche are becoming less likely.   

Surprisingly shallow snow pack on the upper parts of Bacon Rind.  South of Skillet area in the meadows.  2-3 foot depth max at 8800 on a SE aspect.  10+ inches of newer snow on top of a well developed surface hoar.  A semi-supportable crust below that with facets to the bottom.  ECTP 11 really surprised us, failing on the surface hoar.  Challenging skiing staying on top and did some base damage on rocks even up high.  Log jam roller coaster back down to the car. Still a fun outing.  Send us snow!  And keep up the good work!

We rode up Denny Creek to the local's route. Coverage was thin, but passable as we left the Denny and worked up through the trees. The trail hadn't been set in yet this season. We didn't go far once we arrived in the openings below the ridge because visibility was poor. No avalanches or red flags for instability observed (but poor visibility). 

The snowpack was weaker than everywhere else Alex and I have been this year. The snowpack remains thin (60-80 cm). The post-Thanksgiving dry spell resulted in a well-defined layer of surface hoar and near surface facets. Below that the base of the snowpack transitioned to large grain sugary facets and depth hoar. Resting on all this weak snow was a cohesive slab. In the non-wind-loaded terrain where we rode, the snowpack seemed to have adjusted to the current load (ECTNs in the high teens to 20s, PST 30/100 arrest). However, new or wind-drifted snow would upset this delicate balance. We avoided wind-loaded terrain where avalanches would be most likely, though this was partially because our planned route simply didn't intersect with commonly wind-loaded slopes. 

While snowpack tests were not propagating failure today, just a few inches of snow (over 0.3" SWE) would change the picture. The danger would increase and collapsing and human-triggered avalanches would become likely. 

On the drive we saw one small wind slab in Yellowstone that looked 1-3 days old (photo attached).

Visibility improved on the drive back, with high clouds, and we looked towards Lionhead with Binoculars from the highway and did not see any avalanches.

Snow surface soft with ~3" of new, mod-strong SW winds at 11am 

Reactive tests in snowpits with low to moderate ECTP scores.  HS 105, NE aspects at 9480'.  

Experienced collapsing on the north end of Rob's, likely failing on buried surface hoar that was evident in pit.  

We toured above 9000' on a W to SW aspects on Henderson Mtn.  We experienced several collapses and had propagation in multiple ECTs performed.  HS varies between 85-105cm.  Snowpilot pit is from 9820' W aspect, photo from 9940': both with ECTP results.  

Snow surface variable with wind boards and radiation crusts, mixed with soft snow in shaded aspects.