Warming will seriously test the snowpack in the coming days and will likely produce destructive slab avalanches. It might feel like spring, but the snowpack is far from settled.
Strong southwest winds have been redistributing loose surface snow into wind slabs in the lee of exposed terrain features. Wind slab releases could step down to a buried weak layer to create a much larger avalanche.
Forecast warming will test 30 cm and 50 cm-deep layers below the recent storm snow as well as the January crust 80 - 130 cm deep. Smaller avalanches may also step down.
Solar warming will work to destabilize snow on sun-exposed slopes sheltered from wind. Wet snow may shed naturally or with a human trigger.
No new avalanches were reported Tuesday.
On Monday, avalanche activity reached size 2.5, with natural avalanches occurring during heavy snowfall and strong winds. Avalanches were triggered within the storm snow and on buried weak layers.
Check out this MIN report of a remotely triggered avalanche near Cranbrook. Photo below
While natural activity is expected to taper off, human triggering remains a concern.
By Thursday, a new melt-freeze crust should glaze the surface on solar aspects and below about 1800 m. The depth of affected snow should increase over the coming days, although crust recovery may be weak. This process will affect 30 to 60 cm of settling recent snow, which is wind-affected at higher elevations. About half of it overlies a crust formed early in the storm. It otherwise overlies faceted snow.
A persistent weak layer of preserved surface hoar or facets from late January is buried 80 to 130 cm deep. This weak layer is expected to remain reactive as forecast warming tests the snowpack. The lower snowpack is generally well-settled.
Check out this MIN for an overview of conditions around Tunnel Creek.
Wednesday Night
Increasingly clear. 30 to 40 km/h southwest ridgetop wind, increasing. Freezing level to 1200 m.
Thursday
Sunny with possible valley cloud. 40 to 50 km/h southwest ridgetop wind, up to 90 km/h in high alpine. Freezing level rising to 2200 m, remaining elevated overnight. Treeline temperature around 2 °C.
Friday
Sunny. 20 km/h southwest ridgetop wind. Freezing level rising to 2500 m. Treeline temperature 5 °C.
Saturday
Sunny. 10 to 20 km/h west ridgetop wind. Freezing level to 3000 m. Treeline temperature 6 °C.
More details can be found in the Mountain Weather Forecast.
