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RegisterFeb 11th, 2022–Feb 12th, 2022
Purcells.
When in doubt ride simple terrain. The likelihood of triggering avalanches could change rapidly with warming and solar input. There is some uncertainty in where and when slab properties could exist above the late January layer. Use caution at treeline and avoid overhead hazard.
Friday night: no new snow expected. Moderate northwest winds in the alpine. Low of -11 at 1700m.
Saturday: sunny with the possibility of a temperature inversion and freezing levels rising to 1500m in the north and 2000m in the south of the range. Light to moderate northwest winds in the alpine.
Sunday: mix of sun and clouds with freezing levels rising to 1500m. Light northwest winds shifting to west in the afternoon.
Monday: light precipitation bringing trace amounts of snow. Light west winds and freezing levels rising to 1200m.
On Thursday loose wet avalanches were observed up to size 1.5 on solar aspects at lower elevations. One size 2 wind slab avalanche was triggered by explosives on a morainal feature at 2200m.
On Wednesday in the southern part of the forecast region a skier triggered a size 2 wind slab avalanche in a steep rocky feature at 2600m on a east aspect. This avalanche ran on the mid January crust.
On Tuesday several small cornice falls were observed triggering slab avalanches up to size 2 in lee and cross loaded features at treeline and above. A skier triggered a size 1.5 slab avalanche on a steep treeline feature on a south aspect, this avalanche ran on the late January layer.
This MIN post from the Dogtooth shows the type of open slopes where the buried surface hoar may be reactive at lower elevations.
A new melt-freeze crust is expected on solar aspects into the alpine and on all aspects below treeline. This crust will likely break down and become moist as the freezing level rises and the sun comes out. Previous strong wind from the southwest through northwest have formed wind slabs at higher elevations and over hanging cornices on some ridge features.
The January 30 interface is now typically down 20-50cm and consists of a melt-freeze crust on solar aspects extending into the alpine, surface hoar in sheltered areas at and below treeline, and small facets in some areas.
Several old surface hoar layers are now buried in the upper snowpack 40-120cm deep.
The early December crust/facet layer of concern sits around 80 cm deep in the eastern Purcells and shallow terrain, and up to 150 cm in the west. This layer produced numerous large avalanches in January but is now considered dormant. See this forecaster blog on how to manage this layer as it may come into play again later this season.