Expect storm slab reactivity to increase throughout the day as new snow accumulates and winds increase. Avoid shallow, variable, rocky slopes where deep weak layers remain a major concern.
Expect storm slab reactivity and size to increase throughout the day. In sheltered terrain, slabs may be overlying a weak layer of surface hoar.
Human triggering of deep weak layers remains possible in terrain with shallow, variable snowpacks. Where supportive to riders, a melt-freeze crust may be providing a bridging effect, making it more difficult to trigger deeper layers.
A number of natural and rider-triggered storm slab avalanches have been reported since Monday. Several of these have released on a layer of preserved surface hoar roughly 30 cm below the surface.
Evidence of instabilities deep in the snowpack continue to be reported. On Tuesday an avalanche was triggered by a snowcat around 1800 m. Although it did not propagate, it did fail deep, near the base of the snowpack.
Please continue to share any observations or photos on the Mountain Information Network.
Expect surface slab development throughout Thursday with forecast snow and wind. This will further bury a layer of large surface hoar in wind-sheltered terrain, down 30 to 40 cm. A melt-freeze crust is buried by roughly 60 to 80 cm. This crust ranges from 2 cm at higher elevations to 10 cm at lower elevations. Below the crust, the mid-snowpack is generally well consolidated. A weak layer of facets and a crust near the bottom of the snowpack remains a concern.
Treeline snow depths are roughly 150 to 200 cm.
Wednesday night
Mostly cloudy, with no precipitation. Light to moderate ridgetop winds. Treeline temperatures 0 to -5 C.
Thursday
Cloudy with light snow, 5 to 10 cm. Moderate south ridgetop winds. Treeline temperature 0 to -5 C.
Friday
Cloudy with snow. 10 to 25 cm overnight, and another 5 to 10 cm throughout the day. Moderate to strong south ridgetop winds. Treeline temperatures around 0 C. Freezing levels 2000 m.
Saturday
Cloudy with snow, 10 to 15 cm. Moderate south ridgetop winds. Treeline temperatures around 0 C. Freezing levels 1500 m.
More details can be found in the Mountain Weather Forecast.
