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Avalanche Forecast

Archived

Dec 19th, 2022–Dec 20th, 2022

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

Regions

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

Enjoy the fresh snow but don't let it lure you into unsafe terrain.

Wind-affected terrain may have produced fresh wind slabs. Buried weak layers are still triggerable.

Confidence

Moderate

Avalanche Summary

As of this writing, no new avalanches were reported in the last 24 hours. With recent low-density snow continuing to fall and winds picking up, expect this to change.

Persistent slab avalanche activity has continued to taper off but these layers will likely remain triggerable in specific terrain features.

Snowpack Summary

In the alpine and at treeline moderate to strong northwest winds have redistributed the recent low-density snow (up to 35 cm) and formed fresh wind slabs. On steep solar slopes, these new wind slabs and fresh snow will be sitting on a thin sun crust. In more sheltered areas, the new snow covers surface hoar and facets.

The snow further down is more settled and it may overlie another layer of surface hoar or thin sun crust, although it does not appear to be widespread. Both were formed in early December, and are now buried 50 to 60 cm deep.

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. At the bottom of the snowpack, a thick crust sits on the ground.

At treeline, snowpack depths vary from 100 to 200 cm.

Weather Summary

Monday Night

Cloudy with some clearing, up to 2 cm accumulation, 20 km/h west wind, -25 C at 1500 m.

Tuesday

Cloudy, 10 to 15 cm accumulation, 15 to 25 km/h east winds, -25 C at 1500 m.

Wednesday

Sunny with cloudy periods, no accumulation, 20 to 30 km/h northeast wind, temperature -30 C at 1500 m.

Thursday

Mostly sunny, no accumulation, 15 to 20 km/h north winds, -30 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the old surface.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • In times of uncertainty conservative terrain choices are our best defense.
  • Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.

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.