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Avalanche Forecast

Archived

Feb 23rd, 2022–Feb 24th, 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.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

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

There is recent evidence that the persistent avalanche problem can still be human triggered in parts of our region.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Light flurries overnight. Light southwest winds. Alpine lows of -20. 

THURSDAY: Partly cloudy, light northwest wind, alpine high of -11.

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.

Avalanche Summary

On Tuesday there was a small natural wind slab reported in the Lizard Range, as well as some small (size 1) skier-controlled wind slabs. On Monday 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 an old buried 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 moderate to strong northeast winds and formed 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.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Be aware of the potential for large avalanches due to the presence of buried 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.