Avalanche Forecast

Issued: Mar 29th, 2014 9:12AM

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.

rbuhler, Avalanche Canada

South Columbia.

Highly unpredictable 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

Weather Forecast

A weak band of moisture will cross the interior on Sunday resulting in light precipitation. On Monday, a ridge of high pressure will build and should persist for a few days. Sunday: Precipitation: 3-6mm, freezing level am: 1100m pm: 1400m, ridgetop wind: light SWMonday: Mainly dry, clouds clearing during the day, freezing level am: 900m pm: 1600m, ridgetop wind: light SW-WTuesday: Sunny, freezing level am: surface pm: 1600m, ridgetop wind: light variable

Avalanche Summary

A low probability, but high consequence avalanche problem plagues the Columbia regions. These highly destructive and largely unpredictable avalanches are expected to be isolated, but certainly possible anywhere at any time. Avalanches continue to step down to old, deep weak layers. The most recent was a natural size 3 in the Cariboo region on Thursday. The S Columbia had one step down on Tuesday and the N Columbia on Monday. While these layers are typically dormant, they are expected to become reactive again with the new loading or the upcoming strong solar inputs.Reports from Friday for the South Columbia include isolated human and explosive triggered avalanches up to size 1.5 in the recent storm snow down around 20cm. Loose sluffing from steep terrain features was also reported.

Snowpack Summary

Recent warm temperatures have resulted in good settlement and improved bonding of the storm snow from earlier in the week, and human-triggering has generally become stubborn. 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 may still be 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

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.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

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.>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.>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 30th, 2014 2:00PM