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Avalanche Forecast

Archived

Dec 22nd, 2022–Dec 23rd, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

carefully assess each slope for wind slab. wind slab avalanches have the potential to step down to deeper layers.

Confidence

Moderate

Avalanche Summary

On Tuesday explosive control produced a few small avalanches, up to size one. No other recent avalanches have been reported.

Snowpack Summary

Variable winds mean that wind slab could be found on all aspects at treeline and above. These new slabs will form over facets, surface hoar or a crust meaning they will not bond well.

Around 50cm overlies a layer of surface hoar at treeline and a thin crust on steep south facing slopes. This layer was formed in early December and is less widespread than the other layers of concern in the snowpack.

The mid-November layer consisting of facets and surface hoar is now buried around 80 cm deep. These depths will vary throughout our region with decreased depths in the northern areas.

The snowpack in the forecast region is quite variable and increasingly complex with snowpack depths at treeline varying from 100cm to 200cm.

Weather Summary

Thursday Night

Flurries bringing trace amounts of new snow.. Light westerly winds and a low of -30 at 1800m.

Friday

Cloudy with up to 5cm of new snow expected. westerly winds increasing throughout the day to strong . High of -22 at 1800m.

Saturday

Mostly cloudy with around 5cm of new snow expected. Strong southwest winds and a high of -16 at 1800m.

Sunday

Mostly cloudy with light flurries bringing trace amounts of new snow. Strong westerly winds and a high of -10 at 1800m.

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.
  • Closely monitor how the new snow is bonding to the old surface.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.