Avalanche Forecast

Issued: Jan 2nd, 2015 7:54AM

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

jfloyer, Avalanche Canada

South Columbia.

A crust/surface hoar layer from mid-December remains the primary concern and requires careful terrain selection. New snow may conceal wind slabs in exposed terrain.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

Saturday: mostly cloudy with flurries. Treeline temperatures around -11C and winds light or moderate from the west. Sunday: Dry in the morning with light snow in the afternoon. Treeline temperatures around -12C, winds light and variable. Monday: 20-30 cm new snow expected by the end of the day Monday. Freezing levels are expected to start low on Monday and start to rise, climbing to around -5 or so by the end of the day. Ridgetop winds are expected to rise to around 60 km/h from the southwest.

Avalanche Summary

Persistent slabs continue to be triggered by skiers, vehicles and remote triggers (from a distance away). These have been up to size 2.5 and failing 50-70 cm down on the mid-December crust/surface hoar layer. Many of these have been around treeline elevation, although some smaller sized avalanches were triggered as low as 1750 m. Several size 1-1.5 wind slabs also failed naturally or with skier triggers following strong northerly winds.

Snowpack Summary

Up to 15 cm fell in the north of the region, while the south saw only a few cm during the storm that ended Friday. The new snow has been added to an already volatile snowpack. Winds were sufficiently strong to set up new wind slabs in exposed areas mostly on east-facing aspects, but previous wind slabs on south-facing aspects remain a concern and may now be buried by a small amount of new snow, making them harder to spot. Storm slabs or wind slabs may be easy to trigger, and could step down to a persistent weak layer from mid-December that comprises of a crust with well-preserved surface hoar crystals sitting above it. It is most prevalent between 1700 m and 2200 m and has been the weak layer responsible for a large number of natural and human-triggered avalanches over the last several days. A hard rain crust with facets from early November is buried more than a metre down and is currently unreactive.

Problems

Persistent Slabs

An easily-triggered and prominent layer of surface hoar overlying a crust is buried typically around 60-80 cm below the surface and is still producing avalanches, especially on steep, convex terrain around treeline.

Stick to small features with limited consequence and be aware of what is above you at all times.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Storm Slabs

In the north of the region, sufficient new snow has fallen to be concerned with both storm slabs and wind slabs. In the south, less new snow fell, but fresh winds have set up wind slabs in exposed lee terrain on a variety of aspects.

Avoid recently wind loaded features.>Choose well supported terrain without convexities.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Jan 3rd, 2015 2:00PM