Avalanche Forecast

Issued: Jan 21st, 2016 8:39AM

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

pgoddard, Avalanche Canada

Purcells.

Weather on Friday looks quite variable across the Purcells. In the south and west, increased loading from snow and wind could drive danger ratings higher than posted.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Friday brings another 5-15 cm snow, moderate SW winds and freezing levels around 1500 m. Through the weekend, expect mainly light winds, cool temperatures, cloudy skies and a few flurries.For more details check out http://www.avalanche.ca/weather.

Avalanche Summary

On Wednesday, explosives triggered three size 2 wind slabs. On Tuesday, skiers who ventured onto a steep alpine feature in a permanently closed area within a ski area triggered a size 1.5 wind slab.On Monday, several small slabs were triggered by skiers, including three that were remotely triggered. These were either on wind-loaded features at and above treeline, or in openings at low elevations, where buried surface hoar is largest and most reactive. Snow and wind this week could overload the persistent weak layer in some parts of the region.

Snowpack Summary

Conditions are variable across the Purcells. New wind slabs are developing at treeline and alpine elevations. In some areas, these overlie a surface hoar or crust interface and may be extra touchy. The persistent weak layer from early January is around 20-40 cm down and has not yet reached tipping point in many parts of the region. With warming, snow and wind forecast on Friday, a consolidated persistent slab could form. Operators are also still keeping an eye on a more deeply buried layer of surface hoar from December, which is now considered dormant or unreactive. In general, the mid and lower snowpack are well settled and strong.

Problems

Wind Slabs

Wind slabs are building on lee features. These may be extra-reactive where they overlie buried surface hoar.

Be cautious as you transition into wind affected terrain.>Travel on ridgetops to avoid wind slabs on slopes below.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

With each successive snowfall, a slab is gradually forming above a touchy buried weakness. This could be triggered by the weight of a person, even from a distance.

Be aware of the potential for remote triggers and wide propagations.>Avoid open slopes and convex rolls at and below treeline, and north-facing alpine slopes, where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Jan 22nd, 2016 2:00PM