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Avalanche Forecast

Archived

Feb 2nd, 2024–Feb 3rd, 2024

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell, Bull.

Small but reactive wind slabs may form as storm snow accumulates.

Continue to avoid large and consequential terrain while the snowpack cools and strengthens.

Confidence

Moderate

Avalanche Summary

Natural avalanche cycles continued throughout this week with rain, warming, and sunshine weakening the upper snowpack. Wet loose and slab avalanches were reported to size 3. Natural activity has tapered off as temperatures gradually cool.

Moving forward avalanche activity will become more likely as storm snow accumulates.

Snowpack Summary

5-15 cm of new snow is expected to accumulate over Saturday. This will fall over moist snow at low elevations, or over a crust at higher elevations.

The top 50 cm of snow at treeline is moist with several layers of crusts and facets below. At the base of the snowpack, weak faceted grains and depth hoar is present. These layers may strengthen as the temperatures cool, however, we have significant uncertainty about the reactivity of these layers moving forward.

Weather Summary

Friday Night

Cloudy with up to 3 cm of new snow expected. Locally heavier amounts may be seen, up to 15 cm is possible near Invermere. Freezing levels remain above 1500 m overnight. Light and variable winds.

Saturday

Cloudy with up to 5-15 cm of new snow expected in most areas favoring the eastern slopes of the Purcells. Northeast winds start light and increase over the day to 40 km/h. Freezing levels around 1500 m, treeline temperatures near -4°C.

Sunday

Mostly cloudy with up to 5 cm of new snow expected. Freezing levels around 1300 m, treeline temperatures around -6°C. Light and variable winds.

Monday

A mix of sun and cloud with possible flurries. Freezing levels drop to 1000 m. Southeast winds 10-20 km/h.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be aware of the potential for surprisingly large avalanches due to deeply 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.

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.