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Avalanche Forecast

Archived

Feb 24th, 2022–Feb 25th, 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.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

Watch for lingering pockets of wind slab on various aspects in exposed terrain and around ridgelines.

There is some recent evidence that the persistent avalanche problem may still be rider triggered in parts of our region.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT: Partly cloudy, light southwest wind, alpine low of -16.

FRIDAY: Mix of sun and cloud. Light to moderate southwest wind. Alpine highs of -10.

SATURDAY: Mix of sun and cloud, moderate southwest wind, alpine highs of -7.

SUNDAY: Increasing cloud, moderate southwest wind, alpine highs to -4.

Avalanche Summary

There were small pockets of wind slab triggered by skiers on Wednesday. Also on Wednesday, the South Rockies team experienced whumpfing and cracking in places where the late January surface hoar is still preserved and reactive in snowpack tests, but they didn't see any new avalanches (check out their MIN).

Earlier in the week a skier accidentally triggered a wind slab on a reverse loaded feature in the Lizard Range (MIN here). On Saturday there was a machine triggered avalanche on surface hoar layer in an open gully feature in the Rolling Hills area.

Snowpack Summary

The 10-30 cm of most recent snow has been redistributed by recent variable winds and has built wind slabs in unusual places. In south-facing terrain, new snow sits on top of melt-freeze crusts, and in open terrain recent snow sits over old firm wind-affected surfaces.

A buried surface hoar layer may be found 30-60 cm deep on sheltered, north-facing treeline-type features. This distribution of this layer is spotty in nature but has recently produced avalanches, whumpfing and snowpack test results in the Flathead. 

The lower snowpack is well consolidated, with a crust/facet layer found near the bottom of the snowpack. It is currently considered dormant but could become active later this season. Check out the forecaster blog for more information. 

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Even a small avalanche can be harmful if it pushes you into an obstacle or a terrain trap.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.

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.