Avalanche Forecast

Issued: Dec 5th, 2018 4:43PM

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

ghelgeson, Avalanche Canada

South Rockies.

While unlikely, it may be possible to trigger large avalanches in steep, smooth, alpine bowls where a dense slab rests on a weak base. Watch for isolated wind slabs near ridgecrest in the alpine too.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

This benign blocking pattern will be with us for the foreseeable future. Things begin to change on the Coast this weekend, but no precipitation is expected to make it to the South Rockies. Unfortunately it looks like a heap of wind is coming our way Saturday night through at least Monday. WEDNESDAY NIGHT: Freezing level at valley bottom, light northwest wind, no significant precipitation expected.THURSDAY: Scattered cloud cover, clearing in the afternoon, freezing level at valley bottom, light north/northwest wind, no significant precipitation expected.FRIDAY: Clear skies, freezing level at valley bottom, light to moderate wind generally out of the west, no significant precipitation expected.SATURDAY: Scattered cloud cover, freezing level at valley bottom, light to moderate southwest wind, no significant precipitation expected.

Avalanche Summary

No new avalanches have been reported in the region. If you have been out, please submit any observations to the Mountain Information Network MIN.

Snowpack Summary

The region received up to 20 cm of snow over the past seven days. Isolated pockets of stiff wind slab may exist on leeward slopes. Below the surface exists a series of crusts and a feathery surface hoar layer. We have a lot of uncertainty around the weak surface hoar layer and its distribution, but it's most likely present on sheltered slopes in the alpine and at treeline. A mixed layer of melt-freeze crusts and sugary facets buried late October can be found at the base of the snowpack at treeline and in the alpine. This layer has not been active, but there is potential for slab avalanches on this layer given the current snowpack structure. Terrain features like smooth alpine bowls with variable snowpack depths would be most suspect.Average snowpack depths at treeline are near 50 cm and taper quickly as elevation decreases. Snow depths below treeline are generally below the threshold depth required to produce avalanches.

Problems

Wind Slabs

Wind slabs are likely growing old and tired, but this a classic Rockies scenario where wind loaded features are some of the only rideable pieces of terrain. Human triggering would be most likely immediately lee of ridgecrest and in extreme terrain

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Increase your caution as you transition into wind affected terrain.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Valid until: Dec 6th, 2018 2:00PM