Avalanche Forecast

Issued: Feb 7th, 2013 9:19AM

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.

mpeter, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Friday: Expect overcast conditions with a chance of isolated flurries, moderate westerly winds and alpine temperatures reaching -5.Saturday & Sunday: A ridge will build giving mostly clear skies, light west/southwest winds and alpine temperatures reaching -2 in the afternoons.

Avalanche Summary

A natural cycle has passed with windslab avalanches at treeline and in the alpine up to size 2.5 and loose wet sluffing at lower elevations. Isolated rider controlled avalanches up to size 1.0 in wind loaded areas have also been reported.

Snowpack Summary

Dribs and drabs of light precipitation is tapering off. Consistent southwesterly winds have maintained snow transport, and many areas show layers of windslab over windslab. Some places have seen swirling winds creating cross and reverse loading on isolated slopes. The deepest storm interface (from the very beginning of this storm cycle) includes a huge variety of old surfaces from facets to crusts and isolated pockets of surface hoar (sheltered treeline and below treeline). There is very limited information with regards to this interface, with the only results suggesting reactivity in sheltered, shady treeline and below treeline slopes (likely associated with the preserved surface hoar pockets). I would stress the importance of digging down to find and test weak layers. A cautious and curious approach is critical.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

Problems

Wind Slabs

New snow and strong shifting winds have built wind slabs that are likely found behind terrain breaks such as ridges and ribs.

Assess start zones carefully and use safe travel techniques.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Persistent Slabs

Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls, especially at treeline and below treeline elevations.

Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 8th, 2013 2:00PM