Archived

Avalanche Forecast

Nov 26th, 2014–Nov 27th, 2014

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Columbia.

Winter storm conditions have produced a dangerous storm slab which sits on a touchy weak layer. Now is a good time to avoid avalanche terrain and stick to low angle slopes.

Confidence

Fair

Weather Forecast

A warm, moist Pacific storm will continue to bring moderate-heavy precipitation to the southern interior on Thursday. An Arctic high pressure system should arrive on Friday morning bringing cold, sunny conditions for the weekend. Weds. Night/Thursday: Precipitation 15-25mm, freezing level around 2000m, ridgetop wind strong SW Thurs. Night: Precipitation 6-12mm, ridgetop wind strong SWFriday: A mix of sun and cloud, light flurries possible, freezing level valley bottom, ridgetop wind easing during the daySaturday: A mix of sun and cloud, treeline temperature around -10C, ridgetop wind calm

Avalanche Summary

On Monday and Tuesday, explosive control at a ski area produced widespread storm slabs up to size 2. On Tuesday, Glacier National Park reported numerous natural avalanches up to size 3. Observations are still very limited but it is expected that avalanche activity is occurring throughout the region. As new snow continues to accumulate, natural avalanche activity is expected to continue and the size of these avalanches will continue to increase.

Snowpack Summary

Around 80-100cm of recent storm snow sits on the mid-November drought layer (facets, surface hoar, and/or a sun crust on steep southerly slopes). 20-30cm below this layer is a thick rain crust with weak facets on top. In the Rogers Pass area, the storm slab is poorly bonded to the mid-November layer and snowpack tests suggest it can be triggered easily with wide propagations possible. In some tests, the deeper crust/facet layer was also failing and it is possible that avalanches may step down to this layer.Check out Parks Canada Mountain Safety Facebook Page for a couple videos of their snowpack tests on Tuesday.Recent strong and variable winds have created wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. At lower elevations expect travel to be difficult and potentially hazardous as many early season hazards are exposed or lightly buried (stumps, logs, rocks, open creeks, etc).

Avalanche Problems

Storm Slabs

The storm slab sits on a touchy weak layer and is expected to become very reactive with additional storm loading. Recent wind loading has created wind slabs in leeward features which are expected to be very touchy.

Be alert to conditions that change with elevation.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 3 - 5

Loose Dry

Be cautious of loose sluffing from steep terrain as new snowfall continues. Rain at lower elevations may cause loose wet activity.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3