Avalanche Forecast

Issued: Dec 2nd, 2013 8:23AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

triley, Avalanche Canada

Kootenay Boundary.

The storm continues to build very touchy slabs above recently buried weak layers. Large avalanches are very likely to release naturally or be triggered by light additional loads.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Overnight and Tuesday: Precipitation 10-15 mm overnight becoming light in the morning as the Arctic ridge moves Southward and collides with the moist Pacific low. Temperatures trending colder as the Arctic air invades and Northeast winds build. Becoming sunny in the afternoon.Wednesday: Cold and clear.Thursday: Cold and clear.

Avalanche Summary

We suspect that storm slab avalanches are releasing naturally up to about size 2.5. If a deeper instability is triggered, expect avalanches to be in the size 3.0 range. This storm needs some time to settle and bond, forecast cold temperatures may preserve recently buried weak layers and require more time to settle and bond than when the post storm temperatures are warm. This is a complex avalanche forecasting scenario; complicated by early season timing when we have few observations coming from the field.

Snowpack Summary

The new storm slab is about 40-60 cm deep depending on where you are in the region. This storm slab has been reported to be releasing naturally during the storm, and is very touchy to light triggers like skiers/riders. Storm slabs are sitting above recently buried weak layers of surface hoar on North aspects and melt/freeze crusts on solar aspects. There are some reports of a deeply buried early season crust that formed in October. We do not know the extent of this layer with respect to aspect and areas within the region. In other regions of the interior mountains, this layer is more likely to be found in the high alpine on northerly aspects.

Problems

Storm Slabs

The new storm slab may be up to 50 cm deep in some parts of the region. This storm slab may release naturally, or be triggered by light additional loads like skiers/riders. Travel on adjacent terrain may trigger avalanches.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>The very touchy conditions require extreme caution if travelling in the mountains.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

Persistent Slabs

If deeply buried weak layers are triggered, expect very large destructive avalanches.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 5

Valid until: Dec 3rd, 2013 2:00PM