Avalanche Forecast

Issued: Jan 3rd, 2018 4:54PM

The alpine rating is considerable, 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.

Summary

Confidence

Moderate - Freezing levels are uncertain on Thursday

Weather Forecast

THURSDAY: Mainly cloudy / light west wind / Alpine temperature 0 with a temperature inversion FRIDAY: Cloudy with sunny breaks / Light west wind / Alpine temperature -2 SATURDAY: Mainly cloudy / Light to moderate west wind / Alpine temperature -2

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 the 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.On Saturday several natural and human triggered storm slab avalanches to Size 2 were reported on a wide variety of aspects and elevations. Furthermore, several persistent slab avalanches to Size 1.5 were reported (with some remote-triggered by skiers).

Snowpack Summary

Up to 45 cm of snow fell on at the end of last week. Since then, strong winds from a wide range of directions have blown snow around: In the south of the region winds were from the south west; whereas in the north the winds were from the north east. The main question in the snowpack surrounds the mid-December layer sitting beneath the recent snow. This layer includes crusts on solar aspects and feathery surface hoar in sheltered terrain at and below treeline, and has consistently shown its reactivity, even on small features below treeline. The lower snowpack is composed of mostly soft sugary snow and a few early season crusts that have not produced significant test results recently.

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.

Choose well supported terrain without convexities.Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Watch for signs of instability such as whumpfing, or cracking.

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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 4th, 2018 2:00PM