Avalanche Forecast

Issued: Jan 4th, 2018 5:18PM

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

mbender, Avalanche Canada

South Rockies.

Expect to continue to see persistent slab avalanche activity as the snow sitting above the persistent weak layer further settles and consolidates with forecast warmer temperatures. Adopt a conservative approach in the coming days.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

FRIDAY: Cloudy with isolated flurries / Light west wind / Alpine temperature 2 SATURDAY: Cloudy with isolated flurries / Light to moderate west wind / Alpine temperature -3 SUNDAY: Cloudy with isolated flurries / Light to moderate west wind / Alpine temperature -5

Avalanche Summary

Continued avalanche activity was observed in steep low elevation terrain (road cut banks) in the Elk Valley on Wednesday to size 1.5. These were triggering very easily. On Monday, a machine triggered Size 1.5 persistent slab avalanche was reported running on the mid December surface hoar layer, down 35 cm at that location (1700m). See the details here in a Mountain Information Network (MIN) post. On Sunday a Size 2 persistent slab (stepping down to late November crust/facets) was intentionally triggered on an east aspect near 2000m in the south of the region. Expect to continue to see persistent avalanche activity continue as temperatures revert to a normal regime (warmer in the valleys and colder with elevation) and snow sitting above persistent weak layers settles more rapidly.

Snowpack Summary

Up to 45 cm of snow fell to end 2017. Since then, moderate to strong winds from a wide range of directions have redistributed that snow into wind slabs tree line and above. The main concern in the snowpack is a weak layer buried mid-December, which consists of a crust on solar aspects and feathery surface hoar in sheltered terrain at and below tree line. This layer has consistently shown to be reactive to human triggers. The lower snowpack is composed of mostly soft sugary faceted snow and a early season crusts.

Problems

Persistent Slabs

A weak layer composed of surface hoar and/or crusts is buried 35-70 cm below the surface. This layer continues to be very reactive to human triggers and may not improve anytime soon.

Watch for signs of instability such as whumpfing, or cracking. Choose supported terrain without convexities at treeline where buried surface hoar may be preservedAvoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Moderate winds have created fresh wind slabs at higher elevations. In the south of the region, the winds were from the south-west. In the north of the region the winds were from the north east.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered, the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Jan 5th, 2018 2:00PM