Avalanche Forecast

Issued: Jan 20th, 2014 8:17AM

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

jfloyer, Avalanche Canada

South Columbia.

Summary

Confidence

Good

Weather Forecast

A couple of small disturbances may bring some freezing drizzle.Tuesday: Dry. An above freezing layer (inversion) is expected from around 2200-2800m with alpine temperatures reaching around 2C. Ridgetop winds westerly 20-30 km/h.Wednesday: Flurries with a chance of freezing drizzle in the north of the region. Light NW'ly winds. Alpine temperatures around -2C.Thursday: Very light lingering flurries. Ridgetop winds light NW'ly. Alpine temperatures around -4C.

Avalanche Summary

There have been no slab avalanches reported in this region since Friday, when wind slab avalanches up to size 2.5 were triggered using explosives. The last reported deep release on basal facets was on Thursday in the south of the region where a snow cat was working on ridge and remotely triggered a size 3 avalanche from 30m away. The avalanche occurred on a southeast facing slope at 2160m.

Snowpack Summary

Roughly 90cm of well settled storm snow exists as a stubborn wind slab in many exposed areas. With recent warming, steep, sun exposed slopes have seen a daily melt-freeze cycle while surface hoar has been growing in some shaded terrain. Below the recently formed storm slab you may find surface hoar buried around January 8th. This interface seems to have become less of a concern for most operations, and is showing mainly moderate to hard resistant planar results in snowpack tests.There are 2 other layers of note which professionals are keeping a close eye on: The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas and may sit well over 200cm below the surface. At the base of the snowpack you may also find the October persistent weak layer which consists of facets sitting on a crust. This layer is predominantly found on northerly aspects at tree line and in the alpine. The depth of both these layers makes skier triggering unlikely (maybe a heavy load on a thin spot in steep terrain, a cornice fall or rapid temperature change). The consequences of triggering either of these weaknesses would be severe.

Problems

Deep Persistent Slabs

Although deep persistent slab avalanches have become less likely, the consequences of a release would be severe. Possible triggers include cornice fall, rapid temperature changes or a heavy load over a thin spot.

Conditions have greatly improved, but be mindful that deep instabilities are still present.>Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Jan 21st, 2014 2:00PM