Avalanche Forecast

Issued: Mar 18th, 2014 8:39AM

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.

Avalanche Canada Peter, Avalanche Canada

Summary

Confidence

Fair

Weather Forecast

Wednesday: Periods of snow – 10-15 cm. The freezing level is near 1000 m and ridge winds are moderate from the W-SW. Thursday: Cloudy with flurries and sunny breaks. The freezing level is around 800 m and ridge winds are light from the NW. Friday: A mix of sun and cloud. The freezing level is around 600-800 m and ridge winds are light from the NW.

Avalanche Summary

There were a couple new reports of natural slab avalanches stepping down to buried persistent weaknesses on Monday. Some of these were on southerly aspects and likely involved buried sun crusts with avalanches up to Size 3. There was one that 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 Friday resulting in one fatality. Some information is available here.The group involved in a very close call with a size 3.5 avalanche in the Ozalenka Valley south of McBride submitted a great incident report. Check it out here. It's an excellent example of the kind of activity we've been seeing throughout the interior in the last week.

Snowpack Summary

Around 30-40 cm of recent storm snow has fallen in the past few days. Periods of strong westerly winds have probably formed fresh wind slabs in exposed lee and cross-loaded terrain. This new snow now sits on a surface hoar and/or sun crust layer. Weakness have been observed within the new snow and at the interface between the new snow and this layer. 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 100cm - 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. Cornices are large and fragile.

Problems

Storm Slabs

An icon showing Storm Slabs
More snow forecast for Wednesday will add to the 30-50 cm of recent storm snow that is sitting on a crust or surface hoar layer. Be particularly cautions on wind loaded features or when the sun pokes out. 
Be cautious as you transition into wind affected terrain.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing 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.
The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches. >Watch for terrain traps where avalanche debris can accumulate into deep deposits.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The early February Persistent Weak Layer is still active and has produced some stunning avalanches recently. Very large avalanches may result from a surface avalanche in motion, a cornice fall or a rider finding the sweet spot.
Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>Avoid rock out croppings, large convexities and anywhere the snowpack is thin and/or variable.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 19th, 2014 2:00PM