Avalanche Forecast

Issued: Mar 19th, 2014 9:13AM

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

Peter, Avalanche Canada

Cariboos.

We should see sunny breaks over the next few days. Brief periods of solar radiation could be enough to trigger stubborn persistent slabs or cause cornice failures. Conservative route selection is crucial at this time.

Summary

Confidence

Fair

Weather Forecast

Thursday: Cloudy with flurries and sunny breaks â€“ up to 5 cm. The freezing level is around 600-800 m and ridge winds are light gusting moderate from the NW. Friday: A mix of sun and cloud. The freezing level is around 600 m and ridge winds are light from the NW. Saturday: Mainly cloudy with sunny breaks and a chance of flurries. The freezing level is near valley bottom. Ridge winds are light.

Avalanche Summary

We continue to see large natural avalanches stepping down to the deeply buried persistent weak layers. On Tuesday there was one report of a size 2.5 remotely triggered avalanche where a group of skiers felt a massive whumpf at the top of a slope and realized that they triggered an avalanche on an adjacent slope almost 500 m away. On Monday there were also a couple reports of large slab avalanches. Some of these were on southerly aspects and likely involved buried sun crusts (early March interface) with avalanches up to Size 3. One was accidentally skier triggered from a Northeast aspect at treeline and likely released on the mid February weak layer. A group of snowmobilers triggered a large avalanche not far from Blue River on March 14 resulting in one fatality. Some information is available here.

Snowpack Summary

Around 30-40 cm of recent storm snow has fallen in the past few days. There may be a variety of layers within the storm snow from thin sun crusts, to graupel balls, and maybe even recently buried surface hoar from brief clearings overnight. Also, expect fresh wind slabs in exposed lee and cross-loaded terrain. This new snow now sits on a surface hoar and/or sun crust layer. Some recent snowpack tests give moderate "pops or drops" shears on the interface between the recent storm snow and previous surface. A couple other notable persistent weaknesses remain a concern in the mid-snowpack. Another surface hoar/sun crust combo buried in early March is now down around 60-80 cm. The February 10th surface hoar/facet/crust combo is 90cm - 150cm below the snow surface and widespread throughout the region. Surface avalanches in motion and cornice fall have the potential to initiate an avalanche on this deeply buried weak layer. The mid and lower snowpack remains weak and facetted in areas with a relatively shallow snowpack.

Problems

Storm Slabs

Weaknesses exist within or under the recent storm snow and could be triggered by the weight of a rider, particularly in steep wind-loaded terrain.

Choose well supported terrain without convexities.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

The early March sun crust/ surface hoar combo should not be underestimated. While there's a lot of uncertainty and complexity surrounding this layer, it's important to note that human triggering is most likely at treeline.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

The deeply buried mid-February persistent weak layer continues to produce large natural and human triggered avalanches. Check out the forecast details tab for more info on recent avalanches.

Avoid rock out croppings, large convexities and anywhere the snowpack is thin and/or variable.>Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 20th, 2014 2:00PM