Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Feb 10th, 2022–Feb 11th, 2022

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

Be extra cautious at treeline where preserved surface hoar is more likely to be found. The likelihood of triggering avalanches could increase as the freezing level rises and the sun comes out.

Confidence

High -

Weather Forecast

Thursday night: no new snow expected. Light to moderate northwest winds and a low of -6 at 1600m.

Friday: sunny with freezing levels around 1500m. Light northwest winds.

Saturday: sunny with light northwest winds. Freezing levels rising to 1500m.

Sunday: Sunny with light northwest winds. Freezing level rising to 1600m.

Avalanche Summary

On Wednesday a size two natural wind slab avalanche was observed in steep alpine terrain on a east aspect.

On Monday explosives triggered numerous cornices, with some subsequently triggering slabs on the slope below. Explosives also triggered a size 3 on the early December crust, this was a reloaded bed surface at 1900m that had previously avalanched.

On Sunday, a ski cut triggered a size 1.5 wind slab at 1950 m on a north aspect which was 15-25 cm thick and a skier accidently triggered a size 2 wind slab which failed down 30-60 cm on the mid-January crust. An explosive-triggered size 2.5 wind slab was also reported which failed on the mid-January crust down 30 cm and then stepped down to an older layer 100 cm deep in the snowpack. 

This MIN report summarizes the recent conditions well and describes natural and human-triggered slab avalanches size 1-2 as well as whumphing and shooting cracks.

Snowpack Summary

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 15-40 cm and consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine and surface hoar in sheltered areas at and below treeline. 

The widespread January 18 rain crust is now around 40-100cm deep with weak faceted snow above. It is most prominent in the Lizard range. In heavily wind scoured areas at and above treeline this crust can be found on the surface. 

The early December crust/facet persistent weak layer is now 100-200 cm deep. 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. 

Terrain and Travel

  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Cornices become weak with daytime heating or solar exposure.
  • Be careful as you transition into wind affected terrain.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.