Kootenay Boundary Avalanche Forecast

Feb 16th, 2020 5:00PM

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

A reactive storm slab formed over the weekend with 20-40 cm new snow. Wind loaded features will have the deepest slabs, but use caution in more sheltered terrain where the new snow rests on a layer of surface hoar.

Summary

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

We’re moving into a dryer period that is expected to be with us for the foreseeable future. Temperatures look very reasonable for the middle of February and there is a fair amount of sun in the forecast for the work week.

SUNDAY NIGHT: Cloudy with isolated flurries. Alpine low temperature -10 C. West-northwest wind 15-25 km/hr.

MONDAY: Mix of sun and cloud. Alpine high temperature -7 C. Northwest wind 15-35 km/hr.

TUESDAY: Mix of sun and cloud. Alpine high temperature -9 C. Northwest wind 15-25 km/hr

WEDNESDAY: Cloudy with sunny breaks. Alpine high temperature -7 C. Northwest wind 15-35 km/hr.

Avalanche Summary

A natural storm slab avalanche size 1-2 cycle occurred overnight Saturday at treeline and above. Explosives on Sunday morning triggered numerous slab avalanches to size 2.

On Saturday, storm and wind slab avalanches size 1-1.5 were triggered by skiers, along with loose dry sluffing in steep terrain. In sheltered terrain, a reactive layer of surface hoar 20-40 cm deep is the suspected culprit. On Friday wind slab avalanches were sensitive to human triggering and explosive control work to size 1.5 on lee aspects above 1900 m.

Explosive work Wednesday produced size 1.5-2 wind slab and cornice avalanches. Several small (size 1) natural and skier-triggered wind slab avalanches have been reported on east/northeast aspects in the alpine over the past few days. At least one of these occurred near treeline and was reported to have slid on a crust buried around 20 cm below the surface.

Snowpack Summary

20-40 cm new snow covered a variety of surfaces: hard wind slabs around ridgetops and northerly alpine features, soft slabs and 10-15 cm of lower density snow in sheltered terrain, a thin sun crust on solar aspects, and scoured features in exposed terrain. Spotty surface hoar has also been reported under the recent storm snow. Westerly winds are impacting loose snow developing wind slabs in lee features at upper treeline and higher elevations.

A thick rain crust to mountain top sits below 25-45 cm of recent storm snow in the east of the region and 40-100 cm in the west. Recent avalanches slid on the crust or released within the storm snow. However, recent information indicates the bond at the crust is improving. Weak facet/crust layers near the base of the snowpack have not been an active avalanche problem recently. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Closely monitor how the new snow is bonding to the old surface.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

20-40 cm recent storm snow accumulated over the weekend. In wind exposed terrain this snow is being formed into slabs by ongoing winds from the southwest, west and northwest. In wind sheltered terrain the new snow may rest on a layer of surface hoar which could make it touchier than expected, especially in the trees.  

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Feb 17th, 2020 5:00PM