Avalanche Forecast

Issued: Feb 27th, 2017 3:08PM

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

shorton, Avalanche Canada

Cariboos.

Danger will increase throughout the week with new snow and strong winds in the forecast. Triggering a deep persistent slab is the primary concern and warrants a cautious approach to terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

TUESDAY: Cloudy with flurries starting in the afternoon, moderate southwest winds with strong gusts, alpine temperatures around -15 C.WEDNESDAY: Continued flurries with 5-10 cm of new snow, moderate southwest winds with strong gusts, alpine temperatures around -10 C.THURSDAY: Another 10 cm of new snow, strong southwest winds,Â alpine temperatures around -8 C.

Avalanche Summary

On the weekend several natural wind slabs in the size 1-2 range were reported in steep alpine terrain. Many parts of the region have a similar snowpack structure to Clemina Creek, where two size 2 snowmobile triggered persistent slab avalanches were reported on Saturday (see MIN report here). Triggering a large deep persistent slab avalanche is a low probability - high consequence scenario that warrants an extra cautious approach to terrain. See here for a list of recent near misses in the Cariboos and North Rockies.

Snowpack Summary

New wind slabs have formed on a variety of aspects in alpine terrain thanks to shifting wind directions. Light flurries over the past week have delivered a total of 15-30 cm of low density snow, while sun crusts have formed on steep south slopes. The recent snow has buried the mid-February interface, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. Some lingering surface hoar layers from January are down about a metre and the weak mid-December facets are down about 1.5 metres. These deep persistent weaknesses still have the potential to react to human triggers.

Problems

Deep Persistent Slabs

A lingering weak layer of facets near the bottom of the snowpack may be triggered in shallow snowpack areas and produce large avalanches.

Avoid lingering in runout zones.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Carefully evaluate and use caution around thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Watch for fresh wind slabs in the immediate lee of ridges and crossloaded alpine terrain.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.Avoid recently wind loaded features.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 28th, 2017 2:00PM