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Avalanche Forecast

Archived

Jan 15th, 2023–Jan 16th, 2023

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

Moderate

Avalanche Summary

On Saturday Several natural size 2 wind slab avalanches were observed. These avalanches occurred on north through east aspects in the alpine, they released on the surface hoar layer from early January.

In addition to these wind slab avalanches a skier triggered a size 2.5 avalanche. This avalanche ran on the facets near the bottom of the snow pack. It was in the alpine on a low angle slope. The slab was a meter deep. Check out the MIN for more details.

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

Snowpack Summary

Wind slabs can likely be found on exposed treeline and alpine terrain features on west, north and east facing slopes. Freezing levels have been variable throughout the region. A crust could be found up to 2000m. Up to 15cm of recent storm snow exists at treeline and above.

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 December. Both these layers are most concerning at treeline and above. There is also a layer of large facets at the bottom of the snowpack that continues to produce avalanches and will likely persist for a prolonged period of time.

In General the snowpack is shallow and weak.

Weather Summary

Sunday Night

Cloudy with flurries bringing trace amounts of new snow. Light southerly winds and a low of -8 at 2000m.

Monday

Mostly cloudy with the possibility of light flurries bringing trace amounts of new snow. Light southwest winds and a high of -5 at 2000m.

Tuesday

Mostly cloudy with the no new snow expected. Light westerly wind and a high of -6 at 2000m.

Wednesday

A mix of sun and cloud with no new snow expected. Light westerly winds and a high of -9 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.