Rising temperatures and strong sun are creating very dangerous avalanche conditions. Large, destructive natural avalanches are likely. Avoid all avalanche terrain.
Cornices are large, looming and becoming weak with warm temperatures and sun. A large cornice fall can be dangerous on its own, and can also trigger deep slabs on slopes below.
Several persistent weak layers exist in the upper meter of the snowpack. As temperatures continue to climb on Wednesday, these layers are expected to fail naturally, producing very large and destructive avalanches.
As temperatures rise, expect a heavy, wet upper snowpack to produce storm slab and loose wet avalanches, especially on sun-exposed slopes.
Widespread large natural avalanche activity was reported on Monday and Tuesday, including wet loose to size 2 and storm & persistent slabs to size 3. On Sunday, an extremely large avalanche, suspected size 4, was observed running to valley bottom and climbing up the other side.
We can expect large, destructive persistent slab avalanche activity to continue as temperatures continue to climb on Wednesday.
A moist to wet upper snowpack snow sits over a crust. Below lies a complex snowpack with several weak layers which are currently concerns for triggering persistent slab avalanches:
Facets/surface hoar/crust from early March buried 40 to 60 cm deep,
Facets/surface hoar/crust from mid-February buried 110 to 130 cm deep, and
Facets/surface hoar/crust from late January buried 120 to 160 cm deep.
This complex snowpack combined with dramatic warming makes travel in avalanche terrain dangerous.
Tuesday night
Clearing skies. 20 to 30 km/h southwest ridgetop wind. Treeline temperature +6 °C. Freezing level rising to 2800 m.
Wednesday
Sunny. 10 to 20 km/h south ridgetop wind. Treeline temperature +9 °C. Freezing level 3100 m.
Thursday
Cloudy with rain turning to snow, 5 to 10 cm. 20 to 40 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level falling to 2000 m.
Friday
Cloudy 5 to 15 cm of snow. 30 to 40 km/h south ridgetop wind. Treeline temperature -1 °C. Freezing level 1000 to 2000 m.
More details can be found in the Mountain Weather Forecast.
