Avalanche Forecast

Issued: Feb 13th, 2015 8:12AM

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

Avalanche Canada pgoddard, Avalanche Canada

A Special Public Avalanche Warning is in effect for this region.

Summary

Confidence

Fair

Weather Forecast

Temperatures start cooling on Saturday with the passage of a cold front. 5-10 mm precipitation is expected with the front overnight Friday/ Saturday, tapering to flurries on Sunday. The freezing level is around 2000 m on Saturday morning, falling towards 1500 m by the end of the day. Monday is dry and cool, with a chance of sun. Winds are light to moderate NW, easing to light by late Sunday.

Avalanche Summary

Skiers triggered a very large (size 3.5) persistent slab on Thursday on a NE aspect in the alpine in the Monashees. It failed on the late-Jan layer. Several large avalanches also failed naturally. Some failed in the recent storm snow, and some were glide crack releases and wet slabs gouging to ground. On Wednesday, a size 2.5 persistent slab failed on a steep shallow rocky feature at 2500 m, approximately 1 m deep. Cornices also collapsed naturally and with explosives over the last couple of days.

Snowpack Summary

More than a week of very warm temperatures has affected the snowpack by moistening upper snowpack layers to around 2300 m. There has been some ongoing reactivity of persistent slabs, perhaps due to warming altering the properties of the slab. Below treeline, the snowpack is probably trending isothermal (zero degrees throughout). In the alpine, wind affected surfaces can be found. Cornices may be large and weak. The late-Jan crust/surface hoar layer, buried up to a metre deep, remains a key concern. Triggering this could produce a surprisingly large avalanche. The mid-January surface hoar is typically down 80-120 cm and is most likely to be triggered from thin or rocky snowpack areas; or perhaps with a cornice fall, or an avalanche stepping down. The mid-December weak layer is down over 120cm, but is generally considered unreactive. As temperatures cool this weekend, conditions should gradually improve, but it's still a trouble-ridden snowpack adapting to change... so give it a bit of time.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Persistent slabs are most likely to be triggered from thin snowpack areas, or with large triggers like cornice fall or an avalanche stepping down.
Avoid common trigger points like convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Wind Slabs

An icon showing Wind Slabs
Wind slabs may be lurking on lee and cross-loaded features in the alpine. Cornices are weak and may collapse.
Give cornices a wide berth when travelling on or below ridges.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 14th, 2015 2:00PM