Avalanche Forecast

Issued: Apr 5th, 2014 9:29AM

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 may become weak as temperatures rise.Fore more insight into the current hazard, check out the latest Forecasters Blog.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A trough of moist air will push across the Province on Saturday and Sunday bringing clouds and precipitation.Tonight: 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 1400m, winds, light gusting moderate to strong from the southwest.Monday: Cloudy with light to locally moderate flurries, some parts of the region may see 25cm of precipitation. Freezing level around 2200m, winds moderate, gusting to strong from the south.Tuesday: Cloudy with flurries. Light to locally moderate precipitation amounts. Freezing levels remain high at around 2100 metres, winds generally light occasionally gusting to strong from the south west.

Avalanche Summary

Avalanche activity has slowed down considerably, but yesterday, 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. With incoming precipitation, strong winds and rising temperatures in the forecast, we expect avalanche activity to ramp up  on Sunday and early in the next week. There is real concern that persistent 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

Recent mild temperatures have contributed to a generally well-settled upper snow pack. Wind slabs have been forming in lee terrain on NW through E aspects at tree line and above as a result of moderate to strong upper level winds associated with the new snow.  Stability will decrease with daytime warming.Three persistent weaknesses to be aware of: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 be reactive to rider triggering in select locations. Sun will increase the reactivity of the storm snow on solar aspects in the afternoon. Sluffing  of new snow can be expected in steep terrain on all aspects.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid regrouping in runout zones.>The new snow will require several days to settle and stabilize.>

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 could trigger a buried deep persistent weak layer and result in a highly destructive avalanche.
Use conservative route selection, stick to moderate angled terrain with low consequence.>Cornices become weak with daytime heating. >

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 can wake up these layers.
Avoid large convexities or areas with a thin or variable snowpack.>Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 6th, 2014 2:00PM