Avalanche Forecast

Issued: Feb 12th, 2018 4:56PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada jmcbride, Avalanche Canada

A strong system with periods of intense snowfall and high winds will increase avalanche danger on Tuesday. Stick to low-angle, simple terrain and avoid areas with overhead hazard. Large avalanches may run long distances.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

TUESDAY: Snow. Accumulation 15-25 cm. Ridge wind strong to extreme, southwest. Temperature -10. Freezing level valley bottom.WEDNESDAY: Mostly cloudy, light flurries. Accumulation trace. Ridge wind light to moderate, west. Temperature -12. Freezing level valley bottom.THURSDAY: Mix of sun and cloud. Ridge wind light, south. Temperature -10. Freezing level valley bottom.

Avalanche Summary

Sunday a remotely-triggered (from a distance) size 1.5, slab avalanche was observed on a southerly aspect at 1700 m. A weak layer buried in early January was the suspected failure plane. A very large, widespread avalanche cycle up to size 4 was observed on Thursday and Friday. Slopes of all aspects and elevations ran full path and reached valley floor. In some cases, mature timber was destroyed. Many of these failed on persistent weak layers, while some involved only the recent storm snow.

Snowpack Summary

Strong north to north-westerly winds have loaded lee slopes with 30-40 cm recent storm snow. Alpine and open treeline areas have seen extensive wind-affect from strong, northerly winds, while a sun-crust has formed on solar aspects. Below the snow surface, several persistent weak layers make up a troublesome snowpack. In the top 1-1.5 m of the snowpack, two surface hoar layers buried in January can be found. Expect to find at least one of these layers on all aspects and elevations.Deeper in the snowpack (120-200 cm deep) is a facet/crust/surface hoar layer from December, most prevalent at and below treeline.Near the base of the snowpack is a crust/facet combo, most likely to be triggered from thin spots in the alpine.All of these layers have produced large avalanches recently. The wide distribution and ongoing reactivity of these layers suggests that avoidance through choosing simple terrain is the best strategy.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow and wind will form touchy storm slabs. These slabs will cover a variety of old surfaces including extensive wind slabs at upper elevations and crusts on solar aspects and at lower elevations. Pay attention to how the new snow is bonding.
Minimize exposure to avalanche terrain during periods of heavy loading from new snow and wind.Give cornices a wide berth when traveling on or below ridges.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Persistent Slabs

An icon showing Persistent Slabs
Several troublesome layers exist in the snowpack and may be reactive to large triggers such as a cornice or storm slab release. Human triggering may also be possible in shallow or thin, rocky areas.
Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for large, deep avalanches.Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 13th, 2018 2:00PM

Login