Avalanche Forecast

Issued: Feb 14th, 2016 8:06AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs, Cornices and Persistent Slabs.

Avalanche Canada rbuhler, Avalanche Canada

The hazard rating reflects conditions in the south of the region where enhanced snowfall is possible on Monday.  Wind slabs are expected throughout the region but if any areas see more than 25cm, a more widespread storm slab problem could develop.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Monday

Weather Forecast

Light snowfall is expected to continue Sunday overnight before a weak ridge of high pressure dries things out briefly on Monday morning. However, the southern part of the region may see enhanced snowfall Sunday overnight and Monday due to a storm tracking through Washington.  The next substantial storm system is then expected to reach the south coast on Monday afternoon or evening. 5-10cm is possible Monday afternoon with freezing progressively climbing to around 1800m by Monday night. Another 20-30cm is forecast for Monday overnight with strong southwest winds in the alpine. Tuesday is forecast to be mainly dry with light alpine winds and afternoon freezing levels around 1500m. A weak storm system is forecast to arrive on Wednesday with freezing levels around 1800m.

Avalanche Summary

On Saturday, a ski cut produced a size 1 slab avalanche in a leeward feature on a northeast aspect at 2200m. The slab was 10-20cm thick. On Friday, ski cuts produced size 1 loose wet avalanches at treeline in the recent storm snow. Rain-soaked lower elevations are unlikely to see much in the way of avalanche activity, but wind slab avalanches will continue to be reactive to human-triggering at higher elevations with ongoing snowfall and wind continuing overnight Sunday. Cornices are reported to large and fragile, and may fail under the weight of a person. Deeply buried persistent weak layers may still be reactive in the region but would probably take a heavy trigger like a cornice fall or smaller avalanche stepping down to cause a deep failure.

Snowpack Summary

Recent snowfall and mostly southwestern winds have formed wind slabs in the leeward features in the alpine and at treeline. High freezing levels (around 1800 metres) has settled the upper snowpack and developed variable crusts due to overnight cooling. New surface hoar has been reported from the Coquihalla area, that may be buried down 20-30 cm. Conditions across the region are variable. Most areas have not had a freeze below treeline since the last wet storm. A crust that formed after a warm storm at the end of January is now down 50-80 cm. and it does not appear to "bridge" the early January weak layer in the Duffey lake area. This deeply buried persistent weak layer from early January appears to be isolated to the north of the region, and is now buried down about 50-80 cm. This layer continues to produce sudden results in snowpack tests and has been responsible for recent destructive avalanches.

Problems

Wind Slabs

An icon showing Wind Slabs
Recently formed wind slabs are expected to be reactive throughout most of the region but a more widespread storm slab problem has the potential to form in the south of the region if we see enhanced snowfall Sunday overnight and/or Monday.
Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

An icon showing Cornices
Looming cornices could collapse, especially during storms or during warm weather.  The weight of a person may be enough to cause a cornice failure.
Give cornices a wide berth when travelling on or below ridges.>Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
While the probability of triggering deeper layers are low, the consequences of such a slide would be large. Most likely trigger points are steep, rocky start zones in lower snow parts in the north of the forecast region (Duffey Lake or Chilcotins).
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 15th, 2016 2:00PM