Avalanche Forecast

Issued: Apr 2nd, 2014 9:13AM

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.

bcorrigan, Avalanche Canada

Cariboos.

Danger may increase on south facing slopes during afternoon warming. Solar radiation could be enough to trigger stubborn persistent slabs or cause cornice failures. Conservative route selection remains crucial at this time.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A Pacific frontal system approaching the coast will spread clouds and precipitation inland over the next few days.Thursday: Cloudy with flurries, some parts of the region may receive 10 to 20 cm of precipitation. No overnight freeze, freezing levels up to 1400m, Winds moderate, gusting to strong from the south west.Friday: Cloudy with flurries, up to 20 cm of precipitation possible. No overnight freeze and freezing levels may go up to 1600m. Winds light, gusting to moderate from the south west.Saturday: Cloudy with flurries. 5 to 10 cm of precipitation in the forecast for the region, daytime freezing level around 1500m, overnight freezing levels will drop close to valley bottom, winds, light to moderate from the south west.

Avalanche Summary

Reports from yesterday of numerous 1 to 2.5 avalanches on north and east aspects, as well as cornice failures triggering avalanches. Neighboring regions have reported large avalanches on north and east aspects. 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

The last storm produced 30-40cm of new snow in parts of the forecast region. Reports suggest there has been moist snow up to 1800m on all aspects and perhaps higher on south facing slopes. Stiff wind slabs exist in lee terrain on NW through E aspects at tree line and into the alpine.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. Newly formed wind slabs may 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, and we have reports of avalanches stepping down to this layer. A mid-February crust/facet/surface hoar layer that we've been watching is now down at least 1.5m and although direct triggering 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

Recent storm snow and wind slabs may still be reactive to human triggers in select locations. Sun will increase the reactivity of the storm snow in the afternoon and sluffing can be expected in steep terrain.

The new snow will require several days to settle and stabilize.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

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.

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 highly destructive avalanches are expected to continue. The variable nature of this problem makes it difficult to predict exactly when and where a large avalanche will occur. Sun and warm temperatures may '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.>Local knowledge of slopes that have yet to avalanche is valuable for knowing which slopes to avoid.>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 3rd, 2014 2:00PM