Avalanche Forecast

Issued: Feb 21st, 2012 9:11AM

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

Avalanche Canada jfloyer, Avalanche Canada

Snow amounts are uncertain. If you wake up Wednesday morning with more than 15 cm on the ground, elevate danger to HIGH for all elevation bands.

Summary

Confidence

Poor - Intensity of incoming weather is uncertain

Weather Forecast

Overnight Tuesday: 10-15 cm new snow expected with freezing levels around 1500 m and strong to extreme westerly ridge top winds. Wednesday: a cold front moving through will bring only light snowfall, say 2-4 cm. Temperatures will drop in the afternoon, with freezing levels lowering to around 800 m. Very windy--expect ridge top winds up to 120 km/h. Thursday: lingering flurries, winds diminishing to moderate northwesterly, and freezing level lowering to around 500 m. Friday: Cloudy with a chance of flurries.

Avalanche Summary

A remote-triggered size 2.5 avalanche was reported from the Northern Elk Valley at 2350 m on Tuesday. The crown was 60-70cm deep and the avalanche initiated in wind slab overlying surface hoar. Numerous avalanches sized 1.5 were reported on Sunday (and likely Monday, although we didn't hear about them) at all elevations and focussed predominantly on easterly aspects. Remote-triggering was reported, where the avalanche was triggered from up to 100 m from where it initiated.

Snowpack Summary

In southern and western parts of the region, 40-50 cm of recent snow sits of a highly reactive weak layer comprising surface hoar (most prevalent in the west of the region), sugary facets on shady northerly aspects and sun crusts on solar aspects. This interface has started to react to human-triggering. Certain features of the reactivity, such as remote triggering and the ability to initiate avalanches on relatively low angled terrain, point to this weak layer shaping up to be quite dangerous. In areas further north, less snow has fallen on this interface--in the northern Elk Valley for instance, only around 15-20 cm lies above this interface. In lower snow areas, avalanche activity will likely lag behind higher snow areas, except for areas which have seen significant wind transport. In general, the mid-pack is quite strong in most locations. However, lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Avalanches have been easily triggered on this layer between 20 and 70 cm below the surface. The highly reactive nature gives the possibility for remote-triggered avalanches as well as propagation into low angled terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Wind Slabs

An icon showing Wind Slabs
Expected strong to extreme winds will set up touchy wind slabs at all elevations.

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Valid until: Feb 22nd, 2012 8:00AM

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