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Avalanche Forecast

Archived

Jan 14th, 2023–Jan 15th, 2023

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

Regions

Purcells, Dogtooth, East Purcell, St. Mary.

Continue to make conservative terrain choices and consider the consequences of a chosen slope avalanching. There is variability in the snowpack throughout the region but what is consistent is that the snowpack is shallower and weaker than average.

Confidence

Low

Avalanche Summary

On Friday ski cutting produced small wind slabs on west, north and east aspects.

On Thursday a skier was caught in a small avalanche at treeline. This avalanche failed on a layer of facets in the upper snowpack. Check out the MIN for more details. A few other similar sized skier triggered avalanches were reported in the region. These other avalanches failed on facet or surface hoar layers in the upper snowpack.

Please continue to share any observations or photos on the Mountain Information Network.

Snowpack Summary

New wind slabs can likely be found on exposed treeline and alpine terrain on west, north and east facing slopes. As the freezing level falls the surface will develop a crust at lower elevations.

There are 2 concerning weak layers in the top meter of the snowpack. The first is a layer of surface hoar from early january and the second is a layer of surface hoar, facets and a crust from late December. Both these layers are most concerning at treeline. There is also a layer of facets at the bottom of the snowpack that will likely persist for a prolonged period of time.

In General the snowpack is shallow and weak.

Weather Summary

Saturday Night

Cloudy with flurries bringing trace amounts of new snow. Light southeast winds and a low of -7 at 2000m.

Sunday

Cloudy with flurries bringing trace amounts of new snow. Light southerly winds and a high of -3 at 2000m.

Monday

Mostly cloudy with flurries bringing a few centimeters of new snow. Light to moderate southwest winds and a high of -5 at 2000m.

Tuesday

A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light westerly wind and a high of -5 at 2000m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Be especially cautious as you transition into wind affected terrain.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

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.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.