Avalanche Forecast

Issued: Mar 15th, 2016 10:01AM

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

jlammers, Avalanche Canada

Cariboos.

As stormy weather tapers-off and a dry ridge gradually builds over the province, solar radiation will become the driver for natural avalanche activity.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Wednesday

Weather Forecast

On Tuesday night and Wednesday morning, expect a mix of sun and cloud with isolated spring "power flurries". Clouds should scatter by mid-day on Wednesday while Thursday and Friday will be mainly clear. Ridgetop winds will be light to moderate from the northwest on Wednesday, becoming generally calm on Thursday and Friday. Daytime freezing levels should sit at about 1200m for the forecast period.

Avalanche Summary

On Sunday, natural and human triggered wind slab activity to size 1.5 was observed on a variety of aspects at treeline and in the alpine. The avalanches formed in response to new snow and wind on Saturday. In one case, a smaller surface avalanche stepped down and triggered a size 3 slab on a southwest facing slope at treeline. It is unknown what interface the larger slab failed on. As stormy weather tapers-off and a dry ridge gradually builds over the province, solar radiation may become the driver for natural avalanche activity.

Snowpack Summary

At treeline and in the alpine you're likely to find wind slabs which formed during Saturday's stormy weather. 50-100cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer seems variably reactive. In other words, it's still really touchy in some places while in other spots it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for very large avalanches. Below this interface, the snowpack is generally gaining strength. At ridgetop, cornices are huge and potentially unstable.

Problems

Persistent Slabs

The late February layer is becoming less likely to trigger, but it continues to surprise riders with large avalanches. I'd aim for well-supported slopes without convexities, and I'd be increasingly cautious as solar radiation comes into play.

Choose well supported terrain without convexities.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

As the sun comes out, surface avalanche conditions will include a mix of wind slabs in high elevation lee terrain, and pushy loose wet activity on steep, sun-exposed slopes. Be alert to conditions that change with aspect, elevation and time of day

Be cautious as you transition into wind affected terrain.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Daytime warming and solar radiation will promote large cornice failures which could, in turn, trigger a large avalanche on the slope below

Cornices become weak with daytime heating, so travel early on exposed slopes.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 16th, 2016 2:00PM