Travel in avalanche terrain is not recommended during the intense storm. A natural avalanche cycle is likely to occur.
Snow switching to rain will rapidly load a buried weak layer of surface hoar. Storm slab avalanches may release naturally. The most problematic terrain features will be wherever the snow surface is relatively smooth and uniform.
Loose wet avalanches are likely wherever rain soaks the snowpack.
Riders observed small slab avalanches on Sunday, failing on the weak layer of surface hoar described in the Snowpack Summary. Check out this MIN for an example.
Avalanche activity is expected to be widespread on Monday night and Tuesday as the weak snowpack is rapidly loaded by snow and rain.
An intense storm will impact the region Monday night and Tuesday, first bringing snow that will quickly switch to rain. This will build on and soak the 20 to 30 cm of snow that overlies a touchy weak layer of feathery surface hoar. Storm slabs are expected to be very touchy to riders with rapid slab development and loading over this weak layer.
The remainder of the snowpack is generally weak and faceted, with a hard melt-freeze crust found near the base of the snowpack.
Snowpack depths are generally between 50 and 80 cm at treeline, with substantially lower amounts as you lower with elevation.
Monday Night
Cloudy with snow switching to rain below approximately 2500 m, accumulation 10 to 20 cm of snow possible at the highest elevations. Southwest alpine wind 40 km/h. Treeline temperature 1 °C. Freezing level rising from 1000 m to 2500 m.
Tuesday
Cloudy with heavy rain or snow, 15 to 30 cm snow accumulation possible at the highest elevations above the rain-snow line. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2500 m.
Wednesday
Cloudy with rain or snow, 20 to 40 cm snow accumulation possible above the rain-snow line. Southwest alpine wind 20 to 40 km/h. Treeline temperature 1 °C. Freezing level 2100 m.
Thursday
Mostly cloudy with 10 to 20 cm of early-morning snow. Northwest alpine wind 20 km/h. Treeline temperature -5 °C.
More details can be found in the Mountain Weather Forecast.
