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

Regions

Purcells.

When in doubt choose simple terrain. The likelihood of triggering avalanches can change rapidly with rising freezing levels and solar input. Use extra caution at treeline and on slopes with overhead hazard.

Confidence

Low - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Thursday night: no new snow expected. Moderate northwest winds and freezing levels falling to near valley bottom.

Friday: sunny with Freezing levels around 1600m . Light to moderate northwest winds.

Saturday: sunny with freezing levels rising to 1500m and the possibility of a temperature inversion. Light northwest winds.

Sunday: Mostly sunny with freezing levels rising to 1500m. Light northwest winds shifting to west in the afternoon.

Avalanche Summary

On Wednesday in the southern part of the forecast region a skier triggered a size 2 wind slab avalanche in a steep rocky feature at 2600m on a east aspect. This avalanche ran on the mid January crust.

On Tuesday several small cornice falls were observed triggering slab avalanches up to size 2 in lee and cross loaded features at treeline and above. A skier triggered a size 1.5 slab avalanche on a steep treeline feature on a south aspect, this avalanche ran on the late January layer.

This MIN post from the Dogtooth shows the type of open slopes where the buried surface hoar may be reactive at lower elevations.

Snowpack Summary

We expected a new crust at and below treeline on all aspects. This crust will likely soften at lower elevations and on sun exposed slopes during the day.

Strong westerly winds have formed wind slabs in exposed terrain at higher elevations and scoured windward slopes.

The January 30 interface is now typically down 20-50cm and consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine, surface hoar in sheltered areas at and below treeline, and small facets in some areas.

Several old surface hoar layers are now buried in the upper snowpack 40-120cm deep. 

The early December crust/facet layer of concern sits around 80 cm deep in the eastern Purcells and shallow terrain, and up to 150 cm in the west. 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

  • Minimize exposure to sun-exposed slopes when the 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.