Avalanche Forecast

Issued: Apr 4th, 2014 9:27AM

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

Avalanche Canada bcorrigan, Avalanche Canada

New snow amounts and rising temperatures are driving the hazard these days. Cornices will become weak as temperatures rise.Fore more insight into the current hazard problems, check out the latest Forecasters Blog.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: Slow moving frontal systems are bringing precipitation into the interior of BC for the next few days.Tonight: Cloudy with flurries, trace of precipitation possible. Freezing level should drop to near valley bottom. Winds light, gusting to moderate from the south west.Saturday: Cloudy with flurries. 5 to 10cm precipitation in the forecast for the region, daytime freezing level around 1500m, winds moderate from the south west.Sunday: Cloudy with flurries. Trace of precipitation, for the region, freezing levels around 1300m, winds, light gusting moderate to strong.Monday: Cloudy with light to locally moderate flurries, some parts of the region may see 20cm of precipitation. Freezing level around 2200m, winds moderate, gusting to strong from the south.

Avalanche Summary

No reports of avalanche activity yesterday, but  today (Friday) a commercial operator reported a size 3.5 natural avalanche, on a north aspect, initiating near ridge top in recent storm snow, then stepping down to the Oct./Nov. basal facets and running full path. There is concern that weak layers will become more reactive with rising temperatures and solar warming. This spring, a low probability, high consequence avalanche problem plagues the Columbia regions. Highly destructive and largely unpredictable avalanches are possible right now.

Snowpack Summary

Convective squalls have produced 5 to 10 cm in the last few days throughout the forecast region. Suncrust from the last clear sunny days, has been buried by convective snow squall activity. Wind slabs still exist (and may be building) in lee terrain on NW through E aspects at tree line and above.Three persistent weaknesses now contribute to a highly variable, complex snowpack.A mid-March sun crust/surface hoar layer down 50-80cm has potential for human-triggering in select locations( New wind slabs have been formed on this layer).An 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. We've received recent reports of avalanches stepping down to this layer. A mid-February crust/facet/surface hoar layer that we've been watching is now down around 1.5m and still producing sudden planar shears in snow pit tests. Although direct triggering of this weak layer has become less likely, a large load like a cornice failure or smaller avalanches gaining mass could trigger this layer and produce very a large and destructive avalanche.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent storm snow and wind slabs may still be reactive to rider triggering in select locations. Sun will increase the reactivity of the storm snow on solar aspects in the afternoon, and sluffing can be expected in steep terrain on all aspects.
Avoid regrouping in runout zones.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Assess start zones carefully and use safe travel techniques.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Weak layers buried earlier this month remain reactive to light triggers on convex slopes, southern aspects, and steep alpine terrain. A small avalanche might trigger a deep persistent weak layer and result in a highly destructive avalanche.
Cornices become weak with daytime heating. >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

An icon showing Deep Persistent Slabs
Isolated large destructive avalanches are expected to continue. The variable nature of the problem makes it difficult to predict exactly when and where an avalanche will occur. New snow loading, sun and warm temperatures could wake up these layers.
Be aware of thin areas that may propogate to deeper instabilites.>Local knowledge of slopes that have yet to avalanche is valuable for knowing which slopes to avoid.>Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>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: Apr 5th, 2014 2:00PM