24-25

After a weekend of stormy weather, dropping about 1 foot of snow (~1" of SWE) on the ground, we toured out to the Throne today to see how the new snow had settled and what the winds had done to it. As we approached the main face, we noted swirling winds transporting a fair amount of snow. Generally, winds blew out of the north with gusts from all sorts of directions throughout the day.

Despite the active snow transport, east facing snow surfaces were still soft with minimal to no slab development. We did not note any signs of instability as we traveled up the face. As we neared the ridgeline and shifted to a more southerly aspect, we noted scalloped and scoured snow surfaces and the development of thin wind skins and a few 1-2" wind slabs. We dug a snowpit on a southerly aspect at 8360' (HS: 212) and got an ECTP12 on an 18" wind slab. This test result, as well as the few small wind slabs we noted were the only signs of instability seen today. We chose to stay off of steep southerly terrain and traveled back to the main face where winds had minimally impacted snow surfaces. 

On the ride out, we had great views of the Bridger Ridge and did not see any signs of new avalanches across this broad area. 

Toured up to the meadows below Ross Peak today.  Didn't see much cracking within the new snow (mostly just directly under our skis).  At around 8000' we found a foot of right side up snow above a crust.  I dug a hand pit below the crust and didn't get any planar failure.  On our way down we started to see the surface snow getting heavier as it warmed up.

We were in a fairly protected zone but saw a few small patches of soft wind slab and noticed snow being transported over the ridge above us when visibility was good.

The snow ranger crew was riding around the Bridgers today and we spotted this slide in the bowl to the south of Hardscrabble peak.  It looked fairly recent (last 2 days) but a little hard to tell due to the new snow since yesterday and blowing snow today.  It seems likely that it is one of the slides reported in an observation yesterday.  We had a nice view of it as we rode out so I figured it was worth a picture.  

As for the riding, there seemed to be about 8-12" of new snow that was bonded to the old surface pretty well.  Best riding was anywhere you could get out of the wind, so sheltered bowls or in the trees.

Large chunks of debris from a natural avalanche in Targhee Creek. Photo: GNFAC

We saw many crowns of wind slab avalanches along Lionhead Ridge. Photo: GNFAC

Cornice collapse and small avalanche at the start of Lionhead Ridge. Photo: GNFAC

I rode into Lionhead head with Ryan, Aaron, and Omar on an avalanche warning day. We went straight to Ski Hill and dug a pit there. With better visibility than I anticipated we dropped down to Denny Creek, travelled up and around to the head of Targhee Creek before dropping down through Targhee and back to the vehicles. During the day ~6" of snow fell with moderate winds. Wind slabs were widespread as we rode, and the surface conditions had stiffened in many locations due to the effects of the strong to extreme winds. 

We saw many R1-R2 wind slab avalanches below the cornice line. Visibility was limited so I won't estimate the exact number, but nearly every time we had good views of the steep faces, we saw cornice collapses, debris, or small crown lines. There were two slides on east aspects that ran closer to full path and piled debris more deeply. I expect that most of these had run within the last 24 hours, but continuing snowfall and hurricane force winds made precisely dating these a challenge (many trees were blown down during the wind event, these too were already somewhat buried). None of the avalanches broke on persistent weak layers as far as I could tell. 

We dug at Ski Hill. Pit results were unremarkable with an extended column test breaking and propagating with an extracurricular ECTP32 on the January facets. The January weak layer was buried a meter deep and was 1 Finger Hardness and had gained strength. However, we wrapped around the corner on our decent and found a shallower slope (1m deep) where Fist Hard facets were capped by a dense wind slab. I did not perform an official ECT, we had undercut the slope with our sleds and were able to knock 5-foot-wide sections of slab off with an arm chop, triggering miniature avalanches that slid easily. This showed us what we needed to know--an avalanche on a steep slope with that structure was likely (see video).