Avalanche Forecast

Issued: Mar 27th, 2014 9:40AM

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.

ccampbell, Avalanche Canada

Cariboos.

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

Friday: Cloudy with sunny periods and isolated light snow flurries in the morning becoming mainly cloudy with light snow in the afternoon. Freezing level reaching 1500 m with light to moderate southwesterly alpine wind. Friday night and Saturday: Mainly Cloudy with light snow bringing 10-15 cm of total accumulation. Freezing level around 1600 m and Moderate SW alpine wind. Sunday: Unsettled conditions with light snow flurries bringing another 5-10 cm. Freezing level dropping to 500 m, and light northerly alpine wind.

Avalanche Summary

Reports from Wednesday include isolated dry loose sluffs in steep terrain. Recent very large deep persistent slab avalanches in the North Columbias and neighboring regions highlight a low probability, but high consequence avalanche problem. These highly destructive and largely unpredictable slab avalanches are expected to be isolated, but certainly possible anywhere at anytime.

Snowpack Summary

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 50-70cm 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

Recent storm snow is highly reactive to human triggers. The size depends largely on the amount of fresh snow, which seems to be drainage dependant, and the degree of wind-loading. Regardless, even small avalanches could easily take you for a ride.

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

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 highly destructive avalanches are expected to continue. But beware, the variable nature of this problem makes it difficult to predict exactly when and where avalanches are going to occur.

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: Mar 28th, 2014 2:00PM