Quick report
With good visibility for the first time since the big storm, I walked up Teton Canyon to look for recent activity. Heading into the South Fork of Teton Canyon, I found a large D3 avalanche that most likely released from the NE side of Treasure Mountain within the past day. This avalanche checked all the boxes for suspect terrain - ridgetop, wind-loaded, steep, and rocky. See the attached avalanche for more information.
Lots of new snow in Teton Canyon from the past two weeks with 4"-5" of new snow from the previous 24 hours. At middle and lower elevations, hand shear tests were non-planar and difficult to move. The new snow appears to be bonding well with the snowpack. Winds were calm in the morning and into the afternoon. Around 3 pm western winds started blowing in the lower elevations. Sun warmed up much of the new snow on solar aspects below 8500'. As winds increased in the afternoon, a melt-freeze crust 1-2 cm thick developed on all the sun-affected snow.
No signs of cracking or collapsing. Observed a large avalanche from the previous day.Weather
- Air Temp
- 29
- Cloud Cover
- few
- Wind Loading
- light
- Snow Avail For Transport
- moderate amounts
Sunny in the morning, transitioning to scattered clouds by the afternoon. Warm temperatures just below freezing. Western winds picked up around 3 pm.
Avalanche
- Size
- D3 R4
- Type
- HS
- Aspect
- NE
- Trigger
- NC
- Elevation
- 9400 ft
Yesterday, a large natural avalanche occurred on an NE-facing slope off Treasure Mountain. Triggered by cornice fall, this avalanche started in wind-loaded terrain and broke down to persistent weak layers taking most of the season snowpack to the valley floor. The cornice failed near the left flank, where the snowpack looked thinner and rockier then propagated to the skier's right into thicker wind-loaded snow. Estimating dimension using some mapping tools, this avalanche is ~650 feet wide and ran ~2400 vertical feet to the valley floor where the toe of the debris is covering the South Teton Trail. Many trees were snapped and uprooted (check the photo where the debris came off a cliff and broke the trees mid-height). There were also a large number of trees uprooted that had no previous flagging on them. There were ~2 inches of fresh snow on the debris, hinting at how recent this avalanche occured. This avalanche checked all the boxes for suspect terrain. The area where this avalanche occurred is very rocky with various cliff bands and rock features making up most of the slidepath. The ridgetop terrain is steep and, due to its aspect, wind-loaded. Large cornices had formed above the start zone and as winds and snowfall continued over the past week, these cornices just reached their tipping point. This location contained all the ingredients to produce a large avalanche. While avalanches like this one will be isolated, instances like this are a good reminder that our snowpack can still produce a very large avalanche.