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Avalanche Forecast

Archived

Dec 12th, 2024–Dec 13th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Glacier.

Avalanche hazard with rise this weekend with a storm forecast to bring snow and strong winds.

Confidence

Moderate

Avalanche Summary

Natural avalanche activity has tapered off with a few size 1-2.5 avalanches observed in the highway corridor in steep/extreme terrain since Sunday.

Artillery control produced excellent results on Tupper and Macdonald Sat night, with most shots producing sz 2 to sz 3 avalanches from steep start zones, running out onto valley bottom fans. Debris moved fast, likely picking up speed and mass on the buried surface hoar.

Snowpack Summary

50-70cm of storm snow sits on a sun crust on steep solar aspects. In sheltered locations, this new snow sits atop surface hoar. Strong SW winds at the end of the storm created surface slab conditions on exposed Treeline and Alpine slopes.

There is a dense, well-settled mid-pack without any significant weak layers.

The Nov 9 crust is down 1-1.5m. The base of the snowpack is comprised of several dense, melt-freeze rain crusts formed in October.

Weather Summary

A weekend storm will bring light to moderate snow Friday through Sunday.

Tonight: Cloudy. Alp Low -6. Light winds, Freezing level(FLZ): Valley bottom

Fri: Cloudy w/flurries. Trace precipitation. Light to Moderate S winds. FLZ: 1300 m

Sat : Flurries, 10-15 cm. Alpine high -5 °C. Moderate gusting to Strong SW winds. FLZ: 1400 m

Sun: Mix of sun and clouds w/flurries. Trace precip. Alp high -9. Light SW winds. FLZ: 900 m

Terrain and Travel Advice

  • Be careful as you transition into wind-affected terrain.
  • Keep in mind that human triggering may persist as natural avalanches taper off.

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.