Avalanche Forecast

Issued: Feb 3rd, 2018 5:56PM

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

Avalanche Canada shorton, Avalanche Canada

Another pulse of snow and wind will create dangerous conditions at higher elevations. Stick to small supported terrain features and avoid overhead hazards like cornices.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The weather in this region will strongly depend on the position of the Arctic front that is pushing in from Alberta. Areas east of the front will have much colder temperatures and potentially heavy accumulations while areas west of the front will be warmer and receive less snow.SUNDAY: Snow increasing throughout the day with 10-20 cm possible by the afternoon and localized heavier accumulations, moderate to strong west wind, alpine high temperatures around -5 C.MONDAY: Flurries easing throughout the day with another 5-10 cm of snow, moderate west wind, alpine high temperatures around -7 C.TUESDAY: Light snow, strong west wind, freezing levels climb to around 1200 m.

Avalanche Summary

On Saturday, several 20-50 cm thick storm slabs were triggered with explosives at treeline elevations. A few natural cornice falls occurred on north and east aspect, one triggering a size 2 storm slab on the slope below.There was a brief break in persistent slab avalanche activity this week. However, on Monday and Tuesday, many large (size 2-3) avalanches were triggered naturally and with explosives. Most of the natural avalanches were triggered by cornices falling and releasing slabs on the December and November layers, producing 150-250 cm thick crowns.

Snowpack Summary

Surface snow conditions are highly variable depending on the position of the Arctic front. The Fernie area experienced warm temperatures Saturday morning followed by a sudden drop to frigid temperatures in the afternoon. The results was a new surface crust below 1800 m. Areas closer to the divide likely stayed cold with low density snow. Higher elevations throughout the region stayed cold and windy, allowing the growth of touchy wind slabs and cornices.For the past month there has been regular avalanche activity on multiple deep weak layers. A layer buried mid-January is composed of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and a sun crust on solar aspects and is 60-80 cm deep. Another surface hoar layer from early-January is 90-110 cm deep. A widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Finally, a rain crust with sugary facets buried in late-November is near the base of the snowpack.The bottom line is the snowpack structure is weak. Human triggering is most likely on the shallower weak layers, but any avalanche has the potential to step down to deeper layers and become much larger.

Problems

Wind Slabs

An icon showing Wind Slabs
Expect fresh wind slabs to develop throughout the day, likely resulting in natural avalanche activity in alpine terrain. Weather forecasts are handling the situation poorly, so some areas may have extra thick and touchy slabs.
Stick to simple terrain and be aware of what is above you at all times.Avoid freshly wind loaded features.Be alert to conditions that change with elevation.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Large avalanches have been running on deep weak layers. Wind loading, fragile cornices, and smaller avalanches are all possible triggers.
Extra caution needed around cornices with current conditions.Avoid areas with overhead hazard.Be aware of the potential for large, deep avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Feb 4th, 2018 2:00PM