Quick report
- Cracking
- widespread
- Collapsing
- Observed
We experienced nearly continual collapsing and associated cracking of the snowpack. Some of these were small and localized, with many other extending tens to hundreds of feet from the triggering location.
Widespread cracking and collapsing, just about everything we touched was collapsing with visible cracking on the snow surface. In places a distinct drop of the slab down into the weak snow below was visible.Weather
Day started clear and very cold, with coldest observed air temp on truck thermometer of -36 F. Cold start to the ride, with temperatures eventually warming up into the single digits F (estimated). Wind were light, increasing somewhat into the afternoon. Light precip started at 1530, with heavier snowfall beginning around 1700. 2-3cm accumulated by 1800.
Snowpack
1/6 weak layer(s) down 40-50cm under a settling slab that grades from F- at the surface to 4F- at the base. There are several interfaces here, from the spits of snow and dry weather in between during the end of December/early January. There are at least two surface hoar layers here. In a pit on an E aspect at 7,600' we found SH, FCsf, and MFcr+FCsf combos all within about 15 cm of each other. ECTs failed repeatedly on these interfaces, often failing simultaneously on more than one of the layers here.
Avalanche
I ( VandenBos) observed the aftermath of a widespread avalanche cycle in the Sawtooth Basin as I drove north from Smiley to Banner. Many large avalanches with crowns extending hundreds to thousands of feet were visible. Most activity appeared to focus on 1/6 interface, though a few deeper pockets may have failed on our basal weak layer (11/30). Large avalanches were visible in both the Sawtooth and Western Smoky Mtns and Banner Summit Forecast Zones. Will have a better sense of the distribution of activity once I have time to dig through photos.