Avalanche Forecast

Issued: Feb 10th, 2019 4:19PM

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

Avalanche Canada dsaly, Avalanche Canada

Strong winds have redistributed loose snow and formed wind slabs. Lingering reactive wind slabs are most likely in wind-loaded areas: below ridgelines, under cornices, and around steep, unsupported features.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

SUNDAY NIGHT: Cloudy with clear periods and isolated flurries in evening, trace accumulation. Alpine temperatures near -18C. Ridgetop winds light from the southeast.MONDAY: Mix of sun and cloud, isolated flurries in evening, trace accumulation. Alpine temperatures near -15C. Ridgetop winds light from the south-southeast.TUESDAY: Cloudy with flurries, 10-20 cm accumulation. Alpine temperatures near -8C. Ridgetop winds moderate from the south.WEDNESDAY: Flurries, 10-15 cm accumulation. Alpine temperatures near -8C. Ridgetop winds moderate from the east-southeast.

Avalanche Summary

Several large (size 1-2.5) natural wind slab avalanches occurred on all aspects at treeline and above sometime late Friday evening. Widespread wind effect was noted through Friday with scouring and wind-loading on a variety of aspects. Small wind slabs (size 1-1.5) were reactive to skier traffic. On Wednesday, a skier remotely triggered a size 1.5 slab avalanche approximately 200 m away from them off the same ridgeline that they were traveling on, the suspect failure plain being the February 1st surface hoar interface that was buried last weekend. Additionally, slab avalanches failing on this layer were also easily triggered up to size 1.5 on north and and east-southeast aspects around 2000 m early in the week. With the cold temperatures and a bit of new snow, loose dry sluffing from steeper terrain features can be expected.

Snowpack Summary

The recent wind event has create a variety of wind affected surfaces: scoured and wind-press in exposed terrain, hard wind slabs in wind-loaded areas and around the alpine, softer wind slabs and loose faceted snow in sheltered terrain and at lower elevations. This wind-affected snow covers on variety of snow surfaces, including buried wind crust on westerly aspects, sun crust on southerly aspects to mountain top, variable wind-affect in northerly terrain, and weak feathery surface hoar crystals in sheltered areas at treeline and below. The snowpack now hosts two buried surface hoar layers. The one that was buried on February 1st (down 20-40 cm) seems to be more predominant and reactive to human triggers than the one buried deeper down (40-80 cm). This deeper layer of surface hoar may be most reactive below treeline on shady aspects but doesn't seem to be a widespread problem in the region. The mid-pack is generally well-settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Shifting winds have formed stiff wind slabs at treeline and above, variable winds will continue to redistribute loose snow and build slabs on all aspects. The most reactive deposits will be in steep, unsupported terrain and immediate lees.
Watch for signs of instability such as whumpfing, or cracking. Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
There is a layer a layer of weak feathery surface hoar 20-40 cm below the surface and another 40-80 cm down. The former most reactive, especially where it is sitting on a crust.
Caution around sheltered open areas at treeline and below including cutblocks, gulleys, and glades.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 11th, 2019 2:00PM