Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Likely
- Dimensione
- 1–2
Three avalanches have been triggered in the past three days:
- Snowmobile triggered avalanche in Mill Gulch, a sub-drainage of Smiley Creek in the Western Smokys (Jan 2)
- Large avalanche triggered remotely from 800-1000' away in the Western Smokys (Jan 1)
- Avalanche remotely triggered from a ridgeline in Anderson Creek north of Baker Creek (Dec 31)
Combined with the triggered slides after Christmas, there have been 6 human-caused avalanches in the past 8 days. These avalanches occurred in two separate zones with somewhat different snowpack properties. But all our forecast zones have one important thing in common: a layer of very weak faceted snow buried 8" to 24" deep. Also of note is that all these slides occurred in upper elevation terrain affected by the wind.
Compared to this bullseye information, the continued reports of collapsing of the snowpack and poor test scores are secondary. But it all points to the same conclusion—we have a tricky and dangerous snowpack. Conditions will become increasingly hazardous during the day today, primarily on upper elevation slopes being loaded by new and windblown snow.
Stick to simple terrain and lower slope angles, and rule out steep, upper elevation slopes that are likely to get loaded by today's storm. Half of the recent avalanches have been triggered remotely—from areas below, above, and to the sides of steep slopes. Be aware of both the terrain you're in, as well as the terrain above you.
ADDITIONAL DISCUSSIONThroughout the day, new snow and moderate to strong westerly winds will be loading and drifting upper elevation ridgelines and exposed slopes. Given the modest snow forecasts, these fresh wind slabs will likely be small. The more significant problem is the added weight on the buried weak layer described above.
(1/1/2021) Sun Valley Heli Ski remotely triggered this avalanche from lower angled terrain 800-1000' away. The group felt a collapse that propagated across the bowl into steeper, wind-loaded terrain. Avalanche released on a 9400', E aspect in the Western Smokys. Photo courtesy of Sun Valley Heli Ski.