Avalanche Forecast

Issued: Dec 2nd, 2012 9:05AM

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

swerner, Avalanche Canada

Northwest Inland.

Limited field observations and reports exist from this region. Conditions may be variable. It is important to be familiar with the snowpack and avalanche problems that may exist in your local mountains.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

A broad upper trough remains just offshore while a cooler, unstable onshore westerly flow will persist and strengthen through Monday. A multitude of systems will bring light –moderate precipitation, and strong SW winds, while the arctic air should be pushed out of the region by Monday. Monday into Tuesday will see the heaviest amount of precipitation during the forecast period. Monday: Fzlvl’s surface, snow amounts near 5 cm, ridgetop winds SE 20- gusting 60 km/hr, and alpine temps -8.Tuesday: Fzlvl’s surface, snow amounts 10-20 cm, ridgetop winds SW 30-gusting to 70 km/hr, alpine temps -7.Wednesday: Fzlvl’s surface, snow amounts near 5-10 cm, ridgetop winds S 30 km/hr, and alpine temps -10.

Avalanche Summary

No new natural avalanches have been reported. Currently, information is extremely sparse for this region. If you have been out exploring the backcountry and enjoying the snow, please share your snowpack and /or avalanche observations with us.Email info to forecaster.ca.

Snowpack Summary

Wind slab instabilities exist in the upper snowpack at treeline and in the alpine. They may be touchy to rider triggers; especially on leeward slopes and behind terrain features where pockets of wind slab easily build. At treeline depths in the southern part of the region range between 70-125 cm, but highly variable in the alpine with deep wind drifts and scoured slopes in exposed areas. Generally, the mid-pack is gaining strength and possibly even bridging the persistent weakness below.Digging down deeper is the early November facet/crust persistent layer. This crust sits near the base of the snowpack down 80-130 cm. Test results on this layer earlier this week produced moderate (drops) I have no current observations to suggest the snow above or below this interface is gaining strength, or weakening. In most areas, because this weakness is located near the ground, any associated avalanche activity will likely be limited to slopes with smooth ground cover.

Problems

Wind Slabs

Wind slabs have formed; especially on lee slopes, gully features, and behind ridges. Natural avalanche activity is possible with continued loading. Rider triggering is likely, especially on steep convex slopes.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Avoid lee and cross-loaded terrain near ridge crests.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Basal facet/crust weaknesses are often prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. They may be difficult to trigger, but deep persistent slab avalanches are often very large.

Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Dec 3rd, 2012 2:00PM