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 21st, 2022–Feb 22nd, 2022

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

Regions

Sea To Sky.

The outflow winds are forecast to peak on Tuesday. Due to the recently shifting wind directions, thin new wind slabs should be expected on all aspects in exposed terrain. 

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Arctic high pressure brings a couple more days of cold conditions before returning to seasonal temperatures by Thursday. 

Monday Night: Clear, moderate to strong NE wind, treeline low around -20 °C.

Tuesday: Sunny, moderate to strong NE wind, treeline high around -12 °C.

Wednesday: Mainly sunny with some cloud in the late afternoon, wind becoming moderate NW in the afternoon, treeline high around -8 °C.

Thursday: Sunny, light to moderate N wind, treeline high around -4 °C.

Avalanche Summary

On Sunday, natural size 1 wind slabs were being observed as well as some isolated natural loose activity. A natural size 2 cornice was also reported which did not trigger a slab. 

On Thursday, a natural icefall triggered a size 2.5 slab avalanche on the slope below. This avalanche was on a northeast aspect at 2100 m. Details were limited but we expect this may have been a persistent slab avalanche. 

Snowpack Summary

The weekend storm produced 5-10 cm of snow with strong southwest wind that likely formed thin wind slabs in exposed terrain. On Monday, the wind switched to a northeast direction causing reverse loading and thin wind slabs should now be expected on all aspects. 

The mid-February crust is down 10-30 cm. This melt-freeze crust is reported to exist on all aspects and elevations, except for some of the highest elevation polar aspects. Facets have been observed above the crust on polar aspects.

The late-January crust/facet/surface hoar interface is buried down 40-100 cm. This layer was most reactive between 1700 m and 2000 m. While this layer now appears to be dormant through most of the region, it may still be possible to trigger it at upper treeline or lower alpine features on polar aspects with a large load like a cornice or in shallow snowpack areas.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Closely monitor how the new snow is bonding to the crust.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

Problems

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.

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.