Avalanche Forecast

Issued: Nov 29th, 2012 9:10AM

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

swerner, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Cool arctic air remains embedded in Northern Regions bringing light snow amounts and moderate SE winds. Strong outflow winds will persist through Friday, easing off Saturday. The arctic air will keep cold surface temperatures through the weekend with no inversions. Friday: FLVL’s surface, snow amounts near 5 cm, ridgetop winds SE 30 km/hr with strong valley outflows, alpine temps -12.Saturday: FLVL’s surface, snow amounts near 5 cm, ridgetop winds SE 20km/hr, alpine temps -10.Sunday: FLVL’s surface, ridgetop winds SE 20 km/hr, alpine temps -11.

Avalanche Summary

No new natural avalanches have been reported. Fresh wind slabs have been observed in exposed areas, but slope testing produced very few results. Storm slab and fresh wind slab instabilities may be easily triggered by a rider.

Snowpack Summary

New storm slabs, and wind slabs continue to form over the next few days, and instabilities are likely to exist. The new snow will add to the variable snow depths, and weaknesses that rest below. 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. A couple of notable weaknesses have been observed in the snowpack: first, a storm snow weakness (may also include small surface hoar) down 40-50cm. Second, a facet/crust combo that formed in early November is now down 40-75cm. This layer has produced moderate "drops" results in recent snowpack tests. Because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, grassy areas, etc.)It will be important to keep tabs on this layer through the next storm cycle, and monitor its reaction to the additional load. Check out the recent forum posts here.

Problems

Storm Slabs

Natural avalanche activity is possible with continued loading from snow and wind. Rider triggering is likely, especially on steep convex slopes. Expect to find wind slabs below ridgecrests, behind terrain features, and in cross-loaded gullies.

Use extra caution during periods of loading from new snow and wind.>Avoid travelling in areas that have been reverse loaded by winds.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Basal facet/crust weaknesses are often prone to remote triggering and step down avalanches, and 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.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Nov 30th, 2012 2:00PM