Avalanche Forecast

Archived

Feb 1st, 2020–Feb 2nd, 2020

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Lizard-Flathead.

Elevations that saw rain on Saturday will trend toward LOW danger with an overnight refreeze. Increased danger will exist in areas where new snow accumulated and has been redistributed by wind, so keep a close eye on overhead hazards.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Saturday night: Becoming clear. Strong west winds becoming light by morning.

Sunday: Sunny. Calm or light southwest winds. Alpine high temperatures around -11.

Monday: Sunny. Calm or light northwest winds. Alpine high temperatures around -12.

Tuesday: Mainly sunny. Light southwest winds, increasing a bit over the day. Alpine high temperatures around -13.

Avalanche Summary

Early reports from Saturday in the Fernie area describe a widespread natural avalanche cycle affecting the region over Friday night, with a mix of storm slabs, wet slabs, and loose wet avalanches reaching size 3. Daytime observations were limited, however the cycle is expected to have eased off as temperatures cooled.

Reports from Friday showed explosives control in the Fernie area yielding storm slabs up to size 2 (large). Crown fracture depths ranged from 10-50 cm, giving good evidence of recent wind redistribution.

While natural avalanche activity is likely to taper off quite sharply now that the storm has ended, human-triggering of new snow accumulations will remain possible at higher elevations on Sunday.

Snowpack Summary

Recent storm snow combined with southwest winds have producing slabs in the alpine and exposed tree line areas. Cornices have been noted along ridgelines. The recent snow covers a temperature crust which formed up to around 1600 m.

The upper snowpack continues to settle in mild temperatures. Several crust layers exist in the mid-pack as a result of previous warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity.

The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although this basal layer has not been an active avalanche problem in the region since December, we may see it show up in avalanche activity from Saturday.

Terrain and Travel

Be alert to conditions that change with elevation, aspect and exposure to wind.
Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.