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Avalanche Forecast

Archived

Dec 26th, 2019–Dec 27th, 2019

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 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.

Regions

South Rockies.

The snowpack is gaining strength but it is still possible to trigger large avalanches. Avoid steep, rocky, and wind affected terrain.

Confidence

Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT: Mostly cloudy, 40-50 km/h wind from the west, alpine temperatures drop to -12 C.

FRIDAY: Cloudy with isolated flurries in the morning then some sunny breaks in the afternoon, 40 km/h wind from the west, alpine high temperatures around -10 C.

SATURDAY: Sunny with a few clouds, 20-30 km/h wind from the west, alpine high temperatures around -12 C.

SUNDAY: Cloudy with some light flurries, 20-30 km/h wind from the north, alpine high temperatures around -8 C.

Avalanche Summary

Avalanche activity is on the decline following the intense storm and avalanche cycle last weekend. During the storm large (size 2) storm slab and very large (2.5-3) deep persistent avalanches occurred naturally. Most notable (and concerning) were reports of deep persistent slab avalanches with avalanche crowns 40-200 cm. Since then, a few size 2 wind slab avalanches have been triggered with explosives. 

While the likelihood of triggering a deep persistent slab avalanche is on the decline, there is still a fair bit of uncertainty about this problem, and the consequences of triggering a very large avalanche are severe.

Snowpack Summary

Upwards of 50-100 cm storm snow is settling around the region. At higher elevations, wind is impacting loose dry snow, and building wind slabs and cornices. Up to 1600 m, rain saturated the snowpack. The bottom 30-50 cm of the snowpack consists of weak facets and crusts, these weak layers are the failure plane for recent large (size 2-2.5) deep persistent slab avalanches. The latest forecaster blog discusses managing this complex avalanche problem (check it out here). Snowpack depths range between 80-200 cm around treeline and taper rapidly below.

Terrain and Travel

  • Avoid steep convexities or areas with a thin, rocky, or variable snowpack.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Minimize exposure to overhead avalanche terrain, large avalanches may reach the end of runout zones.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
  • Cornice failure may trigger large avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.