Avalanche Forecast

Issued: Feb 28th, 2014 8:28AM

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

Cariboos.

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 - Freezing levels are 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. For a more in-depth look at upcoming weather conditions, check out the: WEATHER OUTLOOK Thursday night: Cloudy periods, freezing level at valley bottom, ridge top winds, light to 25Km/h.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/hSaturday: 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, freezing level at valley bottom, light ridge top winds.

Avalanche Summary

Avalanche activity reports have diminished in the last two days, but the persistent weak layer still exists. Solar warming on steep south aspects may trigger avalanches that might "step down" to weak mid -pack and basal layers possibly triggering a very large slide. Conditions are ideal for rider triggering right now. Although the frequency of natural avalanches has gone down recently, the consequences of triggering a large avalanche could be devastating. We are entering a low probability, high consequence period.

Snowpack Summary

The storm slab (surface hoar/facet/crust combo) that was formed following the preceding month of cold, dry weather appears to be gaining strength with settlement and warm temperatures, but don't let that fool you into making the wrong terrain choices. The persistent weak layer remains widespread at all elevations and aspects, and although it is not as reactive as it has been, it's still a very real concern. Large settlements and whumpfs are still being reported. Remotely-triggered avalanches indicate the ability of this weak layer to fail and propagate over large distances. Tricky conditions are expected to remain in place longer than we're normally accustomed to. Some Katabatic (down-flowing) wind slab formation is being reported as well.In many wind loaded areas, a slab of up to 2m thick overlies the persistent weak layer creating conditions for very large avalanches. Winds changing to NE in the coming days may build wind slabs on SW and S slopes.Weak basal facets exist in some areas, but triggering has now become unlikely. For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Persistent Slabs

A dense storm slab from the last series of storms now lies above a tricky persistent weak layer. This slab has shown a propensity for remote triggering and propagating over wide distances. In some wind-loaded areas the slab may be up to 2m thick.

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.>

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. The primary wind direction was south west, but now we have north east winds. This could build cornices in places not normally seen. Cornice failures can produce large avalanches.

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

Likely

Expected Size

1 - 4

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