Avalanche Forecast

Issued: Mar 17th, 2016 10:08AM

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

Purcells.

Solar radiation and increasing freezing levels will increase natural avalanche activity. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches.

Summary

Confidence

High

Weather Forecast

The ridge over the province begins to break down on Friday with increasing clouds on Saturday and perhaps some flurries on Sunday. Expect winds to be generally light and southerly. The BIG news is the increasing freezing levels on Sunday(~2200m).

Avalanche Summary

On Wednesday, a few natural and explosive triggered slab avalanches to size 2.5 were reported on northerly aspects in the alpine. Solar radiation and increasing freezing levels will be the main driver of natural avalanche activity in the coming days.

Snowpack Summary

At ridgetop, cornices are huge and could be become increasingly touchy with forecast solar radiation. Sunny skies have likely promoted a melt-freeze cycle on sun-exposed slopes. 40-80 cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried late February, seems variably reactive. In other words, it's still really touchy in some places while in other places 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 large avalanches. Deeper weak layers from mid-February and early January are now down 50-90cm and 70-120cm respectively. Triggering an avalanche on either of these layers has become unlikely but either still has the isolated potential to produce very large avalanches with a heavy trigger or significant warming.

Problems

Cornices

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

Extra caution needed around cornices with current conditions.>Avoid areas with overhead hazard.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

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.

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.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 18th, 2016 2:00PM