We spotted a healthy sz 2.5 on Tent Ridge during our drive today. While Tent Ridge is a known performer, it is very unusual to have an avalanche of this size so early in the season. Be very cautious on, or near slopes that have the Oct 26 crust.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
Temps will be steady around -10 tomorrow with some light cloud cover and flurries starting mid morning. Amounts won't add up to anything significant. Winds will be light from the west.
Avalanche Summary
The east face of Tent Ridge avalanched sometime within the last 12hours (as of 11am this morning). It was a healthy sz2.5, possibly even a sz3. The debris wasn't visible to confirm. It looked like a cornice and/or rapid warming trigger and appeared to fail on the Oct 26 crust. East aspect and wind loaded from an earlier wind event.
Snowpack Summary
The distribution of snow still varies throughout the range, but in alpine areas along the Spray Range, there is enough snow to make avalanches an issue. Highwood Pass is a bit further behind, but there are certainly areas there that also have enough snow. The alpine snowpack is made up of a few significant layers: The basal layers, the Oct 26 crust, and the surface slabs. The basal layers are already facets and some depth hoar in shallow areas. The Oct 26th crust is an unwanted "gift" from the early September snowstorm. Direct observations are limited, but it seems the crust is intact with facets above and below. This Deep Persistent layer will be the one to watch for some time. It is buried anywhere between 20cm and 80cm in blown in areas. In some areas, there is also a second crust that has been reported.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.