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Archived

Avalanche Forecast

Dec 5th, 2012–Dec 6th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain on Saturday

Weather Forecast

Thursday: The region will be under the influence of a Westerly zonal flow. This will bring cooler temperatures, mainly cloudy skies and continuous light-moderate snow, alpine temps -10, ridgetop winds SE 30km/hr. Friday through Saturday: A weak low pressure system moves into the region bringing moderate snow, ridgetop winds NW 15 km/hr, and alpine temps near -11.

Avalanche Summary

Recent reports of several isolated loose dry sluffs from steep terrain features. For a bit more information in the Hankin Area, check out the Regional Forum Posts.

Snowpack Summary

Wind slab

instabilities are likely to 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. Treeline depths range between 90-125 cm, but highly variable in the alpine with deep wind drifts and scoured slopes in exposed areas. At treeline spotty, isolated areas of surface hoar growth exists (up to 3mm). This is most likely buried down 15-20 cm under the recent storm snow. Snowpack tests on a SE aspect around 1400m  showed CTH (resistant "pop") on an old facet layer 55 cm down, and a rutschblock score of 5. Generally, the mid-pack is gaining strength and possibly even bridging the persistent weakness below.Digging down deeper is the early November facet/crust deep persistent layer. This crust sits near the base of the snowpack down 80-130 cm. Test results on this layer earlier this week produced hard results ("drops"). I have no current observations to suggest the snow above or below this interface is gaining strength, or weakening.

Avalanche Problems

Wind Slabs

New storm slabs and wind slabs have formed, especially on lee slopes, gully features, and behind ridges. They may be touchy, especially sitting on an old buried weak layer (surface hoar). Rider triggering is likely.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

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

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Deep 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