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Archived

Avalanche Forecast

Dec 22nd, 2019–Dec 23rd, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

A huge amount of snow and rain has stressed the snowpack, and overloaded weak layers deep in the snowpack.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

Sunday Night: Flurries, trace to 5 cm. Alpine temperature -3 C. Light south wind with moderate gusts. Freezing level 1600 m.

Monday: Isolated flurries, trace to 7 cm. Alpine temperature -4 C. Light to moderate west wind. Freezing level 1500 m.

Tuesday: Mix of sun and cloud. Alpine temperature -9 C. Light west wind. Freezing level at valley bottom.

Wednesday: Mix of sun and cloud. Alpine temperature -11 C. Light west wind.

Avalanche Summary

A natural avalanche cycle occurred Saturday with heavy loading from snow/rain and wind Friday night and through the day Saturday. 

On Saturday and into Sunday, large storm slab, wet slab and deep persistent avalanches were reported. Explosives triggered storm slab avalanches to size 2 in upper elevations and skiers triggered wet slab avalanches to size 2 at lower elevations. More concerning are reports of both natural and explosives triggered avalanches to size 3 which failed on a deep persistent layer with avalanche crowns 40-200 cm. A complex avalanche problem has developed, read the latest forecaster blog here.

Snowpack Summary

Storm totals of 50-80 cm accumulated in the weekend event. The new snow covered a previously variable and wind-affected surface. Reactive storm slabs have formed, winds are further developing slabs at upper elevations. Rain and warm temperatures over the last 72 hours have saturated the snowpack up to 1600 m. 

The bottom half of the snowpack consists of crusts from November and October and facets near the base, these weak layers are the failure plane for large (size 2-2.5) deep persistent slab avalanches. Snowpack depths range between 80-200 cm around treeline and taper rapidly below.

Terrain and Travel

  • Storm slabs in motion may step down to deeply buried weak layers resulting in very large 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 persistent slab.