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Avalanche Forecast

Archived

Dec 27th, 2021–Dec 28th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Vancouver Island.

Unusual weather makes for unusual avalanche conditions: around 50cm of dry pow is on the ground ready to be picked up by the wind. If the wind strikes for even a few hours expect fat pillows of fresh windslab. An unusual "reverse loading" pattern will result form the north wind.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Monday Night: Wind increasing to strong northwest. Treeline temperatures around -10 to -15 C. Light snow (north) or flurries (south) with up to 5 cm by morning.

Tuesday: Mix of sun and clouds, some of those clouds are low so good chance of sun at higher elevations.. Modrate to strong northwest wind. Treeline temperatures around -10 C. No snow.

Wednesday: Mostly sunny with increasing cloud in the afternoon. Strong northwest wind. Treeline temperatures around -10 C. No snow.

Thursday: Up to 5 cm with a short lived band of moisture blowing through on a strong northwest wind. Temperatures around -10 C.

Avalanche Summary

From the few reports we've received the upper snowpack is unconsolidated so loose dry avalanches (sluffs) have been the primary concern. This will change Tuesday with strong wind forecast: widespread and potentially deep windslabs are expected.

Snowpack Summary

With plenty of soft, light snow available for transport, expect wind slab formation at upper elevations Tuesday morning. A northwesterly wind direction means atypical cross-loading and reverse loading patterns.

20-40 cm now sits over a freezing rain crust below 1500 m and above this elevation it may rest on a layer of large surface hoar crystals. Our field team reported easy shears on this layer in their MIN report last week. You can see photos of the surface hoar prior to being buried by the storm in these MIN reports from Elk Mountain on Monday and Mt Kitchener on Tuesday.

The mid- and lower snowpack are generally well settled.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Avoid freshly wind loaded terrain features.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Sheltered slopes at lower elevations will offer the best riding.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

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.