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Avalanche Forecast

Archived

Dec 23rd, 2022–Dec 24th, 2022

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

Regions

Purcells, Dogtooth, East Purcell, Moyie, St. Mary.

Loose surface snow and light snowfall over the day brings potential for fresh wind slab development.

Plan your backcountry trips with the short and very cold days in mind.

Confidence

Moderate

Avalanche Summary

On Tuesday and Wednesday explosive control in the region produced small avalanches with a depth of 10cm.

Although avalanche activity has tapered off, weak layers still exist in the snowpack that may react to human triggers.

If you are headed into the backcountry please consider filling out a Mountain Information Network report.

Snowpack Summary

Southwest winds continue to move snow (where available as fresh snow or loose surface snow) into wind slabs on north and east facing terrain features. Wind slabs sit over a a layer of facets and surface hoar increasing reactivity.

The main layer of concern is the mid-November layer, which is made up of either surface hoar, facets, or crusts buried 40 to 80 cm deep. Avalanche activity on this layer has tapered off but it could still be possible to trigger this layer in isolated terrain features near treeline.

Alpine snowpack distribution is variable, with depths ranging from 70 to 140 cm.

Weather Summary

Cold arctic air begins to weaken on Saturday, as a warm Pacific low pushes light snowfall and strong winds into the interior this week.

Friday Night

Cloudy with trace amounts of new snow expected. Strong southwesterly winds. Freezing level below valley bottom.

Saturday

Cloudy with flurries bringing up to 5cm of new snow. Strong southwest winds and a high of -20°C.

Sunday

Mostly cloudy with flurries bringing trace amounts of new snow. Moderate southwest winds and a high of -15°C.

Monday

A mix of sun and cloud with trace amounts of snow possible. Moderate southwest winds. Freezing levels rise to 800 m. High temperatures of -5°C expected.

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.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.