Avalanche Forecast

Issued: Feb 12th, 2013 10:11AM

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.

jfloyer, Avalanche Canada

Northwest Inland.

The highest danger exists in western parts of the region that have seen more snow.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Synopsis: A short-lived ridge builds for Wednesday before a series of light precipitation bands move Thursday and Friday.Wednesday: Dry and sunny. Northwest winds around 30 km/h at ridgetop. Freezing level at valley bottom.Thursday: Flurries or light snowfall. Light southwest winds. Freezing level 400m in the afternoon.Friday: Lightsnowfall, 2-5cm. Strong to extreme southwest winds, gusting up to 80km/h at ridgetop.

Avalanche Summary

No recent reports, but we have few observations.

Snowpack Summary

Recent light snow has likely set up new wind slabs in exposed lee areas. Previous buried surfaces lie buried approximately 20-40cm below the surface. These vary from facets to crusts and isolated pockets of surface hoar (sheltered treeline and below treeline). There is very limited information about the nature of the interface, with the only results suggesting reactivity in sheltered, shady treeline and below treeline slopes (preserved surface hoar). I would stress the importance of digging down to find and test weak layers.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. It is worth noting that the snowpack in general is quite shallow compared to averages; triggering the 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 shifting winds have built wind slabs that are likely found behind terrain breaks such as ridges and ribs. Watch for katabatic winds descending from glaciers.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

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 13th, 2013 2:00PM