Avalanche Canada shorton, Avalanche Canada

South Columbia Avalanche Forecast

Jan 10th, 2020 5:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Watch for areas where the new snow feels stiff or slabby and remain cautious of open slopes and convex rolls.

Summary

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

FRIDAY NIGHT: Cloudy with isolated flurries and 5-15 cm of snow, light wind from the southwest, alpine temperatures drop to -12 C.

SATURDAY: Cloudy with scattered flurries and 5-10 cm of snow, light wind from the west, alpine high temperatures around -8 C.

SUNDAY: Scattered flurries with 5-10 cm of snow, light wind from the south, alpine high temperatures around -10 C.

MONDAY: Flurries in the morning with 5-10 cm of snow then sunny in the afternoon, light wind from the west, alpine high temperatures around -15 C.

Avalanche Summary

Avalanche activity is likely on the decline as only moderate accumulations of low density snow are expected over the weekend, although there is uncertainty about whether wind could be forming fresh slabs at higher elevations.

There have been several reports of large (size 2-3) avalanches over the past week from both natural and human triggers breaking 100-150 cm deep on surface hoar layers from mid to late December. These avalanches give clear evidence that the continual loading on this fundamentally weak snowpack structure remains a concern. Within the past week, a few notable deep persistent slab avalanches released on west, north, and northeast facing slopes in the alpine. Characteristics common to these avalanches include wide propagation and full depth avalanches scouring away the snowpack to ground.

Preliminary reports from Friday suggest the most recent low density snow was sluffing and producing thin soft slabs.

Snowpack Summary

Low density snow continues to accumulate. Most areas likely have 20-30 cm of soft snow, but stiffer and reactive slabs could be forming in terrain affected by the wind. Recent storms have buried two layers of surface hoar from late December now down 60-140 cm deep. These layers produced large to very large avalanches across all aspects and elevations over the past week. A facet/crust layer from late November lingers near the bottom of the snowpack. This layer has shown reactivity in isolated, shallow snowpack areas.

Terrain and Travel

  • Sheltered slopes at lower elevations will offer the best riding.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2

Low density snow may be blown into unstable slabs on lee features at and above treeline, especially near ridgetops.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5

Two layers of surface hoar from late December are now buried 60-140 cm deep. Recent large avalanches give clear evidence that these persistent weak layers are still a concern.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 11th, 2020 5:00PM