Avalanche Forecast

Issued: Mar 26th, 2014 9:36AM

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

ccampbell, Avalanche Canada

South Columbia.

Highly unpredictable and largely unsurvivable deep persistent slab avalanches will likely remain a concern for the foreseeable future. Continued conservative terrain selection is crucial for safe travel.

Summary

Confidence

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

Weather Forecast

Thursday: Mainly cloudy with light snow flurries. Freezing level near valley bottoms with light variable alpine wind. Friday: Cloudy with sunny periods and isolated light snow flurries. Freezing level reaching 1500 m with light southerly alpine wind. Saturday: Mainly cloudy with light snow bringing 5-10 cm of accumulation. Freezing level around 1200 m and light SE alpine wind.

Avalanche Summary

Reports from Tuesday include isolated small human triggered wind slab avalanches and dry loose sluffs on northerly aspects, and snowballing, pinwheeling, and sluffing on sun-exposed slopes. Recent very large deep persistent slab avalanches in neighboring regions highlight a low probability, but high consequence avalanche problem that also plagues the South Columbia region. These highly destructive and largely unpredictable avalanches are expected to be isolated, but certainly possible anywhere at anytime.

Snowpack Summary

Warm temperatures and blasts of solar radiation are moistening the surface snow. Weaknesses exist within and under the 40-70 cm of rapidly settling recent storm snow, including small surface hoar, thin sun crusts, rain crusts, and/or small facets. These weaknesses are currently reactive to light triggers, especially on wind-loaded slopes. Some big cornices have also become weak.There are three persistent weak layers that contribute to a highly variable, fundamentally unstable, complex snowpack with step-down potential. The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to human-triggers, but still has the potential to produce large avalanches, and we continue to see fractures stepping down to this layer. The mid-February crust/facet/surface hoar layer is typically down at least 1.5m and direct triggering has become unlikely. However, large loads like cornices or smaller avalanches stepping down can still trigger this layer and produce very large avalanches.

Problems

Storm Slabs

Pockets of fresh soft wind slab are lurking below ridge crests and behind terrain features, and surface snow is sluffing readily on steep slopes. Although generally small, these avalanches could easily take you for a ride.

Be cautious as you transition into wind affected terrain.>On steep slopes, pull over periodically or cut into a new line to manage sluffing.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Weaknesses buried earlier this month remain reactive to light triggers in isolated areas (convex slopes, southern aspects, and higher elevations). Step down potential to deeper persistent weaknesses can result in highly destructive avalanches.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

Isolated very large avalanches are expected to continue, but this highly variable problem makes it tricky to predict exactly when and where avalanches are going to occur.

Be aware of thin areas that may propogate to deeper instabilites.>Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>Local knowledge of slopes that have yet to avalanche is valuable for knowing which slopes to avoid.>Avoid large convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Mar 27th, 2014 2:00PM