Avalanche Forecast

Issued: Feb 1st, 2016 7:47AM

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

pmarshall, Avalanche Canada

Northwest Inland.

It won't take much new snow, wind, or warming to tip the balance and activate the lurking persistent weakness in the snowpack. Cautious decision-making is crucial.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Tuesday: A mix of sun and cloud. The freezing level is at valley bottom and ridge winds are light or moderate from the SW-SE. Wednesday: Cloudy with light snow â€“ 3-5 cm. The freezing level is at valley bottom and winds are moderate from the S-SE. Thursday: Cloudy with light snow. The freezing level could rise to 1000-1200 m. Winds also rise to strong from the SE-SW.

Avalanche Summary

On Saturday, there was one report of an intentionally skier triggered size 2 slab avalanche in the Ashman area. This slide may have released on the buried mid-Jan surface hoar layer, down around 50 cm in this area. There was also a report of a size 2.5 slab that was remotely triggered from the far SW corner of the region on Sunday. This slide initiated on the mid-Jan layer and likely stepped down to the Boxing Day surface hoar layer.

Snowpack Summary

Generally 5-20 cm of new snow has accumulated this week. At higher elevations this snow may be covering previously wind affected snow or settled old snow. Below 1200-400 m the new snow probably sits on a crust. Fresh soft wind slabs are likely in exposed lee terrain. The early or mid January surface hoar layer is reported throughout the region and is generally 30-50 cm deep. Observers have found this persistent weakness on all aspects and at all elevations. It consistently produces moderate "pops" results in snowpack tests. Below this, the Boxing Day surface hoar problem may also be lurking. The mid and lower snowpack is generally quite weak and faceted, especially in lower snowpack areas.

Problems

Persistent Slabs

New snow has been slowly accumulating over a layer of facets and surface hoar, and in many places the overlying slab may now be primed for human triggering.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Be aware of the potential for large, widely propagating avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Wind Slabs

Triggering fresh soft wind slabs may be possible in exposed lee terrain near ridge crests, especially on steep unsupported slopes.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 2nd, 2016 2:00PM