Avalanche Forecast

Archived

Jan 3rd, 2020–Jan 4th, 2020

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

South Columbia.

The snowpack will take time to adjust to the load from recent snowfalls. In the meantime continue to choose conservative terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Friday Night: Flurries, accumulation 5-10 cm. Alpine temperature -4 C. Moderate to strong west wind. Freezing level 1200 m.

Saturday: Flurries, accumulation 5-10 cm. Alpine temperature -4 C. Moderate southwest wind. Freezing level 1400 m.

Sunday: Flurries. Alpine temperature -9 C. Moderate west wind.

Monday: Mainly cloudy with scattered flurries. Alpine temperature -6. Moderate southwest wind.

Avalanche Summary

There was a widespread natural and explosives triggered storm slab avalanche activity to size 2.5 and 3 on Wednesday and Thursday. Avalanches were 30-60 cm deep and were reported on all aspects and elevations. Additionally there were several human triggered avalanches reported up to size 2. Some of these were remotely triggered (from a distance). There was a skier remote triggered size 2.5 storm slab avalanche on Tursday in the very south of the region in at 2100 m on a north aspect. This is suspected to have run on surface hoar buried 45 cm deep.

Snowpack Summary

60-110 cm of new snow fell through the last week. All this recent snow has buried a layer of surface hoar found at all elevations. In some places the surface hoar may be combined with a crust on steep sun-exposed aspects.

Another weak layer that was buried around December 27 is a further 20-30 cm below and may present as surface hoar in sheltered areas, sun crust on steep solar aspects and/or a melt freeze crust below 1700 m.

An additional layer of surface hoar buried mid December is 130-200 cm deep. Avalanche activity on this layer has tapered off, but there is still concern for heavy loads to step down to this layer. A crust from late November is now over 200 cm deep. Concern for this layer is limited to rocky or variable snowpack depth areas in the alpine where it most likely exists as a combination of facets and crust.

Terrain and Travel

Be alert to conditions that change with elevation and wind exposure.
Avoid freshly wind loaded terrain features.
Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.