Avalanche Forecast

Issued: Jan 25th, 2016 8:27AM

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

rbuhler, Avalanche Canada

Cariboos.

The current conditions require restraint and conservative decision-making. Triggering the weak layer is getting more difficult but large avalanches, even from relatively low-angle slopes, remain possible. New wind slabs may also form on Tuesday.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A weak storm pulse is expected to bring 5-10cm of new snowfall to the region on Tuesday. Freezing levels are expected to be around 1500m and alpine winds are forecast to be moderate to strong from the southwest. A mix of sun and cloud is expected for Wednesday with freezing levels reaching around 1500m and light to moderate southwest winds in the alpine. A more substantial storm front is expected to reach the region on Wednesday night or Thursday morning. 15-25cm of snowfall is currently being forecast with freezing levels around 1700m and strong southwest winds.

Avalanche Summary

On Sunday, a skier remotely trigger a size 1 avalanche on a NW aspect from 10m away. The slab was 60cm thick which suggests that it failed on the early January surface hoar layer. Natural loose avalanches up to size 2 were also reported from extreme terrain and did not trigger any slabs below. Widespread natural avalanche activity up to size 3 was reported on Friday and Saturday. The majority of this activity occurred on the early January surface hoar layers and the slabs typically varied from 70-120cm thick. There are also several great Mountain Information Network posts in the Cariboos from the weekend which you should check out. Natural activity tapered off since Saturday but the persistent slab is expected to remain reactive to human triggering for several more days. New wind slabs may form on Tuesday with the progression of the weak storm system.

Snowpack Summary

Recent snowfall and strong winds have created some storm slabs but reactive wind slabs on features lee to the southerly winds seems to be the bigger concern in the upper snowpack. This new snow has also added load and stress to the already volatile persistent slab. There are a couple of highly reactive layers of surface hoar typically down 70-100cm which have been responsible for numerous recent large avalanches. The persistent slab is ripe for human and natural triggers and is especially touchy at and below treeline. The mid and lower snowpack below these layers is generally well-settled and strong, with any old weak layers considered dormant for now. Snowpack depths are variable and shallow snowpack areas may have weak facetted crystals near the ground.

Problems

Persistent Slabs

Large avalanches have been failing on a buried persistent weak layer down 70-100 cm. This problem will likely remain sensitive to human triggers for the next few days.

Use conservative route selection and be aware of the potential for remote triggering. >Extra caution required in open terrain features at and below treeline. >Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

New wind slabs may form in leeward features on Tuesday. It may still be possible to trigger deep older wind slabs in exposed lee and cross-loaded terrain near ridge crests.

Use ridges or ribs to avoid pockets of wind loaded snow. >Avoid freshly wind loaded features. >Be cautious as you transition into wind affected terrain. >

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Jan 26th, 2016 2:00PM