Avalanche Forecast

Issued: Mar 2nd, 2017 3:54PM

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

Avalanche Canada cgarritty, Avalanche Canada

The increasing likelihood of waking up a deeply buried weak layer needs to factor into your terrain selection on Friday. A smaller storm slab release may be the perfect trigger.

Summary

Confidence

High -

Weather Forecast

Thursday night: Flurries bringing approximately 5 cm of new snow. Strong to extreme southwest winds. Friday: Periods of snow bringing 10-20 cm of new snow. Winds moderate to strong from the southwest. Freezing level to 1200 metres with alpine temperatures of -8. Saturday: Cloudy with flurries bringing about 5 cm of new snow. Winds light from the southwest. Freezing level back to valley bottom with alpine temperatures of -11. Sunday: A mix of sun and cloud. Winds light to moderate from the southeast. Alpine temperatures of -11.

Avalanche Summary

Two natural slab avalanches were reported in the region on Wednesday, running Size 1.5-2. The larger of these was noted to have occurred in steep, crossloaded terrain. Several natural loose dry avalanches were also observed running to Size 1.Backcountry users in the Cariboos should be aware that many parts of the region have a similar snowpack structure to Clemina Creek, where two size 2 snowmobile triggered persistent slab avalanches were reported on Saturday (see MIN report here). On Monday, another size 2 persistent slab avalanche was accidentally triggered by a skier northwest of Valemount. Triggering a large deep persistent slab avalanche is an ongoing low probability - high consequence scenario that demands an extra cautious approach to terrain selection in our region. See here for a list of recent near misses in the Cariboos and North Rockies.Looking forward, Friday's weather can be expected to produce very touchy avalanche conditions, especially in wind affected areas. Avalanche danger will also increasingly affect lower elevation terrain where loose dry and storm slab avalanche hazards continue to build.

Snowpack Summary

Ongoing snowfall has already brought 15-30cm of new snow to the mountains, and more is on the way. The new snow has been accompanied by moderate to strong southerly winds, which has promoted the formation of touchy wind slabs in lee terrain at upper elevations. The new snow has buried faceted surface snow, as well as surface hoar recently reported in sheltered areas in some parts of the region. A thin sun crust may also exist below the new snow on steep solar aspects. About 50cm below the surface you'll likely find the mid-February interface, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. The reactivity of this layer is still being monitored, and it's worth keeping an eye on as it gets loaded by more snow. Some lingering surface hoar layers from January are down about a metre and the weak mid-December facets are down about 1.5 metres. These deep persistent weaknesses still have the potential to react to human triggers or smaller storm slab avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
Ongoing snowfall and high winds will steadily increase avalanche danger over the day on Friday. Warming temperatures and winds are expected to promote touchy, 'upside down' snow conditions that lead to easy human triggering.
Use ridges or ribs to avoid pockets of wind loaded snow.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A weak layer of facets near the bottom of the snowpack continues to surprise backcountry travelers. The risk of triggering a deeper weak layer will be increasing while new snow continues to fall. The greatest risk exists in shallow snowpack areas.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Avoid lingering in runout zones.Avoid or use extreme caution around thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Mar 3rd, 2017 2:00PM