Avalanche Forecast

Issued: Mar 28th, 2014 9:18AM

The alpine rating is high, 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 practically 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 night and Saturday: Mainly Cloudy with light snow bringing 10-20 cm (or more) of total accumulation (drainage dependant). Freezing level around 1500 m and Moderate SW alpine wind. Sunday: Unsettled conditions with snow flurries bringing another 5-10cm to some areas. Freezing level around 1500 m and Moderate SW alpine wind. Monday: A mix of sun and cloud with isolated light flurries. Freezing level around 1500 m and light wind.

Avalanche Summary

Reports from Thursday suggest that natural storm and wind slab avalanche activity is tapering off, but fresh slabs and loose surface snow remain sensitive to human triggers, with avalanches up to size 2.5. 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

Weaknesses within and under the 40-70 cm of rapidly settling recent storm snow are currently reactive to light triggers, especially on wind-loaded slopes. Three persistent weaknesses 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

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.

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

Possible - 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.

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 29th, 2014 2:00PM