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Archived

Avalanche Forecast

Jan 27th, 2015–Jan 28th, 2015
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
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

The cooling has started, but it may take a couple of days to recover from the very warm air and high freezing levels.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The freezing level is expected to drop overnight down slightly below 1000 metres and then rise again on Wednesday up to 1500 metres. Expect valley cloud in most areas with clear skies above 1500 metres combined with light winds on Wednesday. The freezing level should drop down to valley bottoms by Thursday morning and then rise up to about 1000 metres during the day. Valley cloud may persist with clear skies and light winds above. Southwest winds should develop on Friday as cloud moves into the region ahead of the next Pacific front.

Avalanche Summary

On Monday there were several size 2.0-2.5 loose wet and wet slab avalanches released with explosives at Kootenay Pass, and a size 3.0 natural avalanche in the backcountry near Whitewater ski resort on a Southeast aspect with a very wide propagation that probably released on the mid-January persistent weak layer during a period of strong solar radiation. Moist or wet loose snow avalanches have been reported from several areas up to size 2.0 over the past few days during the warming event. On Saturday a skier triggered a size 2 persistent slab which failed on the mid-December layer. This was a surprising result because it was on a well-supported, concave terrain feature (which had also been heavily skied).

Snowpack Summary

The recent snow overlies various surfaces including surface hoar, a thin crust, or a settled slab. Warm temperatures are affecting the surface layers and turning them moist or wet. Continued warming has increased the likelihood of triggering the persistent weak layer of mid-Jan surface hoar layer which is down about 20-60 cm. These large, well-preserved surface hoar crystals sit on a thin crust up to about 1900m on north aspects and all the way to ridgeline on south aspects. A deeper crust/surface hoar combo buried in mid-December is typically down 80-120cm and has produced some large avalanches recently.

Avalanche Problems

Persistent Slabs

Continued warming from high freezing levels and strong solar radiation may result in natural avalanches releasing on the buried persistent weak layer on Southerly aspects. Avalanches may be human triggered on all aspects.
Stick to small features with limited consequence.>Choose well supported terrain without convexities.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Loose Wet

Moist or wet loose snow is expected to continue to release from light additional loads, or from strong solar radiation on Southerly aspects. 
Be aware of party members below you that may be exposed to your sluffs.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Very warm temperatures and high freezing levels may result in deeply buried weak layers reacting to large loads like cornice falls or from light loads in thin snowpack areas.
Avoid common trigger points such as convexities, thin or variable snowpack areas and around rocks.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 3 - 6