Wind slabs continue to be reactive to skiers in loaded lee pockets at higher elevations. The new storm is expected to increase avalanche danger on Friday.
Confidence
Moderate - Due to the quality of field observations on Tuesday
Weather Forecast
Mostly clear with some valley cloud on Wednesday morning. Light northeast winds becoming light northwest by Wednesday evening. No new snow expected and alpine temperatures around -20. Light snow starting Thursday evening combined with moderate southwest winds and alpine temperatures around -15. Overcast with light snow on Friday with alpine temperatures closer to -10.
Avalanche Summary
On Sunday, explosives and ski cutting in the north of the region produced wind slab avalanches up to size 2. These wind slabs were on northerly aspects and were typically 10-20cm thick but one was reported to be up to 40cm thick. On Tuesday, the wind slabs that formed over the weekend are expected to remain reactive to human-triggering. These wind slabs are expected to be most reactive on north through east aspects in the alpine.
Snowpack Summary
The weekend storm system brought 20-40cm of new snow to the region with strong southwest winds in the alpine. The resulting wind slabs are thickest and most reactive on north and east aspects in wind exposed terrain. The mid-November crust is typically down 50-80cm. Weak facet crystals are reported to be forming above and below this crust layer. With the ongoing cold weather, continued faceting is expected around this layer and it has the potential to create a persistent slab problem in the future.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.