Quick report
- Cracking
- specific
Objectives: Determine how much new snow had fallen in this storm and whether it was loose or formed a slab. Was there any wind effect? See if we could locate the Thanksgiving Drought Layer (TDL) and test it's reactivity.
Results: Above 6500', roughly 1' (30cm) of new snow had fallen Tuesday, 12/31, and overnight into New Year's Day. However, we did not see failures down 1', but instead observed natural and human-triggered avalanches consistently 15cm or 6" thick in a mid-storm density break. Only around ridgelines near 8000' did we find minimal texture suggesting winds strong enough to transport snow. We had trouble locating the TDL in pits we dug (see snowpack obs), which leads us to think it is gaining strength and we may consider it dormant.
Implications: We closed specific large terrain features at the beginning of the day due to the amount of new snow. Given the consistent thickness of the soft slab avalanches that we observed in the field, we felt comfortable skiing avalanche terrain while exposing one person at a time.
The riding was excellent.
See avalanches tab for natural and human-triggered slides. Shooting cracks up to 5' long were observed in the new snow on convexities.Weather
- Air Temp
- low of 17F
- Cloud Cover
- overcast
- Wind Loading
- light
- Rain Elevation
- Valley bottom
- Recent Snowfall
- 30
- Snow Avail For Transport
- large amounts
Overnight snowfall tapered to light flurries by 9am when we entered the field and a trace accumulation was all that fell during the day. Winds were calm in the AM and light westerly at the ridgeline in the PM.
Snowpack
Stepping out of skis highlighted how much snow we received in the last week. Foot penetration was 30-50cm. Skis sunk in 20cm.
Digging pits at both 7350' NW and 7350' NE revealed a right side up snowpack in the top meter. There was no propagation in failures down 60cm (ECTN26 and ECTN28 dn 60). This may have been the interface that got buried the day after Christmas (12/26), which means there is roughly 2' of settled new snow from that storm.
At 7800' NNE, we found HS300cm total height of snow, while on the windward side (7800' W), there was 135cm. On the NNE site, we found ECTN14 dn 40 and ECTN22 dn 60 on rounded grains size .5-1 (probably the 12/26 interface). The W site had similar results. The Thanksgiving Drought Layer was hard to identify and when we tried to target what seemed like it with a Deep Tap Test down 130cm, we got no result.
Avalanche
- 4 natural soft slab avalanches released in the last 24h. 3 of them (D1) had 6" crowns and 1 (D1.5) had a ~12" crown in a wind loaded slope below a cornice. - 1x intentionally skier triggered soft slab (ASc-SS-R2-D1-S).