Avalanche Forecast

Issued: Mar 19th, 2016 8:43AM

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

jsmith, Avalanche Canada

South Columbia.

Freezing levels spike on Sunday which will increase the likelihood of large natural and human triggered avalanches. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches.

Summary

Confidence

High

Weather Forecast

Freezing levels are forecasted to spike to as high as 2700m on Sunday with cloudy skies and possible flurries overnight. Monday looks cloudy with lowering freezing levels. Tuesday should be clear and cool with freezing levels dropping sharply.Â Light to moderate southwesterly winds until Monday evening when they calm down.

Avalanche Summary

On Friday, several large cornice failures triggered slab avalanches up to size 2.5. Additionally, there was a natural size 3 slab avalanche on a southeast aspect at 2500m. This tells us that the late February weak layer is still alive and well even though it may be difficult to trigger in most areas. Small loose wet avalanches and failing cornices triggering slab avalanches on the late February layer would be on the forefront of my mind as I travel through the mountains this weekend.

Snowpack Summary

At ridgetop, cornices are huge and could become increasingly touchy with rising freezing levels and solar radiation. Old wind slabs still linger on lee features at treeline and in the alpine and may become more reactive with solar radiation. 60-110cm 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 reactive to human triggers 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 to produce large avalanches. Below this interface, the snowpack is generally strong and well-settled.

Problems

Cornices

Rising freezing levels and solar radiation will promote large cornice failures which could, in turn, trigger a large avalanche on the slope below.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Persistent Slabs

Small loose wet avalanches and failing cornices triggering slab avalanches on the late February layer would be on the forefront of my mind as I travel through the mountains this weekend.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

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. Loose wet avalanches may also trigger deep and destructive slab avalanches.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >Sluffs may trigger deeper instabilities.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Mar 20th, 2016 2:00PM