Avalanche Forecast

Issued: Feb 6th, 2013 9:28AM

The alpine rating is considerable, the treeline rating is moderate, 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

Thursday: Expect a mix of sun and cloud. Temperatures will be cool in the morning, but warm to around -3 with the sun’s influence. Expect light northwest winds and no precipitation.Friday: Clouds should build overnight and linger through the day. Light flurries are possible, focussed primarily on west facing terrain. Winds should turn westerly and pick up to moderate values with alpine temperatures reaching -5.Saturday: Clouds linger but precipitation dissipates. Winds turn southwesterly and ease with alpine temperatures reaching around -2.

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.

Snowpack Summary

Dribs and drabs of light precipitation continues. 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.

Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>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 7th, 2013 2:00PM