Avalanche Forecast

Issued: Jan 17th, 2017 4:39PM

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

Avalanche Canada mbender, Avalanche Canada

There is a lot of uncertainty surrounding the intensity of precipitation amounts in the region. Certainly in areas where the freezing level is forecast to rise in combination with the potential for snowfall, the avalanche danger will be elevated.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

WEDNESDAY: Scattered flurries with 5 to 10 cm of new snow overnight Tuesday into Wednesday, moderate to strong southwest winds, freezing level rising to 1500 m and likely higher on the eastern slopes.THURSDAY: Clearing with isolated flurries, strong southwest winds, freezing level around 1500 m.FRIDAY: Mainly cloudy, no precipitation, light westerly wind and freezing level around 1200m.More details can be found on the Mountain Weather Forecast.

Avalanche Summary

A Mountain Information Network (MIN) report from Waterton Park on Friday shows a large size 3 deep persistent slab avalanche triggered by a smaller wind slab on a feature with highly variable snow depths. Although an isolated event, this avalanche highlights the possible consequence of our tricky persistent slab problem, especially with the incoming change of weather.

Snowpack Summary

Recent widespread wind affect in exposed alpine and treeline terrain has formed reactive wind slabs on lee features. The mid pack is quite variable throughout the region and the structure depends on snow depth. In deeper snowpack areas, the snowpack appears to be well settled and right side up with isolated concerns for the mid-December facet layer found 50 to 80 cm deep. In shallow snowpack areas and lower elevations, the snowpack is heavily faceted and there are concerns for the mid-December weak facet layer as well as weak basal facets. If a persistent slab is triggered from thinner snowpack areas it may release on the basal facets resulting in a full depth avalanche. Triggering these deeper weak layers will become more likely this week as warm temperatures soften the overlying slab.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Rapid warming will increase the likelihood of triggering persistent weak layers that have been lingering deep in the snowpack.
Danger exists where denser snow overlies weak, sugary snow below.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs
Although there's not much new snow in the forecast, strong winds will transport loose surface snow and form touchy wind slabs on lee features.
Avoid areas where the surface snow feels stiff or slabby.Use ridges or ribs to avoid pockets of wind loaded snow.Watch for signs of instability such as whumpfing, or cracking.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 18th, 2017 2:00PM