Avalanche Forecast

Issued: Feb 28th, 2014 8:30AM

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

bcorrigan, Avalanche Canada

South Columbia.

Although the frequency of natural avalanches has gone down recently, the possibility of triggering a large, destructive avalanche is still very real. See the Forecasters Blog for more insight into this tricky situation.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The ridge of high pressure continues to dominate the forecast. Dry cold arctic air has moved into the region and will remain for the next few days, then towards the end of the weekend, we will see a return to more seasonable temperatures and precipitation.For a more in-depth look at upcoming weather conditions, check out the: WEATHER OUTLOOK Friday night: Clear with a few clouds, freezing level at valley bottom, no precipitation in the forecast, ridge top winds from the north to 20 Km/h. Alpine temperature inversion.Saturday: Sunny, freezing level at valley bottom, ridge top winds from the north around 15 Km/h.Sunday: Sunny, with a few clouds, freezing level at valley bottom, ridge top winds light to 15 Km/h from the SE.Monday: Cloudy with isolated flurries, 5 to 10cm of precipitation, freezing level at valley bottom, light ridge top winds.

Avalanche Summary

Natural avalanches are still occurring in the forecast area. We've also had reports of cornice failures that triggered avalanches.Conditions are ideal for rider triggering right now. We have received numerous reports of skier triggered avalanches, many of which have released quite deep in the snowpack. Several were remotely triggered from a considerable distance and produced large avalanches.

Snowpack Summary

The storm slab about 1.5 metres thickÂ overlies a persistent weak layer, (surface hoar/facet/crust combo) that was formed during the preceding month of cold dry weather. The storm slab appears to be gaining strength with settlement and warm temperatures but the persistent weak layer beneath it remains widespread at all elevations and aspects. Although this weak layer is not as reactive as it has been, it's still a very real concern. Surface hoar and near surface facetting is occurring on protected/shaded aspects. solar aspects are moist to quite high elevations during the day, with sun crusts forming at night.Large settlements and whumpfs are still being reported indicating the ability of this weak layer to fail and propagate over large distances. Touchy conditions will remain in place for the near future. With the winds changing to north east, wind slab development at tree line may change to south east slopes.In many wind loaded areas, a slab of up to 1.5m thick overlies the persistent weak layer creating ideal conditions for very large avalanches. Weak basal facets exist in some areas, but triggering has now become unlikely.

Problems

Persistent Slabs

A dense storm slab now lies over a touchy, persistent weak layer. This weak layer can be triggered remotely (from a distance) and propagate over large areas. In wind-loaded areas the slab may be up to 2m thick. Use conservative terrain choices.

The new snow will require several days to settle and stabilize.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Use very conservative route selection, stick to simple well supported terrain that is low consequence and free of overhead hazard.>Avoid slopes with glide cracks.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Previous storm winds have created wind slabs on lee terrain features. Initially we had winds from the south and west, but now the winds are from the northeast . This could build wind slabs and cornices on south west facing slopes and ridge tops.

Avoid freshly wind loaded features.>Travel on ridgetops to avoid wind slabs on slopes below.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Mar 1st, 2014 2:00PM