Vail & Summit County
SnowpackJason Konigsberg · Jan 21, 2020 · Vail & Summit County
Weather
A short burst of ~1"/hr snowfall with less than an inch of accumulation. Very mild with no wind.
Snowpack
The snowpack below treeline in this area is generally faceted and topped with 8 to 10 inches of settled storm snow from the last couple of weeks. The storm snow has gained cohesion from recent warm temps and settlement. In areas outside of the investigated recent avalanche activity the snow height is about 115 cm. There are two prominent weak layers- the top of the depth hoar layer at 45 cm from the ground and a buried layer of near-surface facets about 25 cm from the surface. Neither were reactive in stability tests. The snowpack is setup for large avalanches to occur with a significant loading event.---The area with the recent avalanche is very different. In fact there were multiple small avalanches in addition to the one reported yesterday. All were pockety and similar at 20 to 30 feet wide and 1 to 2 feet deep, breaking near the ground. This area had obviously slid in the mid-December avalanche cycle leaving a very thin snowpack. The snow depth prior to the recent snowfall was 12 to 18 inches and very weak. The new snow easily overloaded this thin snowpack collapsing facets above depth hoar and also breaking close to the ground. Snow height above two crowns was 45 cm and 70 cm, much less than areas without December avalanche activity.---It is hard to say that this area is representative of the below treeline snowpack in the zone but it is a good reminder to treat each slope individually. Recreating on slopes nearing 40 degrees deserve an individual assessment. Quick probing would have revealed a shallow and different snowpack. The mid-December avalanche cycle was quite extensive in the Vail/Summit zone and many slopes that slid will be slowly building up a slab over extremely weak snow.