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Archived

Avalanche Forecast

Jan 27th, 2017–Jan 28th, 2017
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

A complex avalanche hazard exists in our region. Wind slabs may be strengthening, but the persistent slab problem will linger much longer. Thin snowpack areas such as the Rossland Range are especially concerning.

Confidence

Moderate - Freezing levels are uncertain on Saturday

Weather Forecast

Friday: Mainly cloudy with isolated flurries and a trace of new snow. Winds light to moderate from the west. Freezing level to 1000 metres with alpine temperatures of -7. A temperature inversion may bring alpine temperatures to +2.Saturday: Cloudy with sunny periods. Winds light to moderate from the west. Freezing level to 1100 metres with alpine temperatures of -2. A temperature inversion may bring alpine temperatures to +2.Sunday: Cloudy with sunny periods. Winds moderate to strong from the west. Freezing level to 1300 metres with alpine temperatures of -1. A temperature inversion may bring alpine temperatures to +2.

Avalanche Summary

Aside from small loose snow releases from steep terrain, no new avalanches have been reported.While the reports are rather dated at this point, two recent avalanche involvements remain worthy of consideration. The first, a skier fatality that occurred on Saturday is that it took place on a S/SE facing aspect near 2050m in a cross-loaded feature in the Ymir area. The second report, found on the MIN, details a cornice-triggered Size 2 on Friday near Cabin Peak in the Bonnington range. The initial failure was in the storm slab on a southeast aspect near 2000m but more significantly was observed stepping down to trigger a weak layer deeper in the snowpack. The involvement of deep snowpack weaknesses is keeping these reports in our discussion in spite of their age.(N.B. An error placing Saturday's fatality in the Rossland Range has been corrected)

Snowpack Summary

A complex and tricky snowpack exists in the Kootenay Boundary region. At the surface, a trace to 15 cm of new snow has fallen over the region over Tuesday and Wednesday, covering surface hoar that was previously observed growing up to 6 mm. Combined with Sunday's 3-12 cm and 35-55 cm from last week's storms, the storm snow forming our upper snowpack now totals a rather variable 40-80 cm. The initial snowfall last week was accompanied by moderate to strong southerly winds, resulting in touchy storm and wind slabs forming and bonding poorly to the previous (January 17) snow surface that includes facets and large surface hoar on sheltered slopes and/or a sun crust on steep sun-exposed aspects. This varied layer continues to give easy to moderate and occasionally sudden results in snowpack tests (down anywhere from 30 to 60cms depending on location). In some areas of the Rossland range, the mid-November rain crust / facet layer is now found down 60-100 cm and has proven reactive with recent loading and warming. In thin rocky areas, particularly in the Rossland range, recent reports include easy sudden collapse snowpack test results on facets down 120-150 cm near the ground.

Avalanche Problems

Persistent Slabs

Several different persistent weak layers are buried 60-150 cm deep and have proven reactive to human triggering. Conservative terrain use is essential in managing the problem, especially in low snow areas such as the southwest portion of the region.
Be aware of the potential for large avalanches due to deeply buried weak layers.Avoid unsupported slopes.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Watch for pockets of wind slab lingering on exposed northerly features near ridge crests, and also in cross-loaded southeast gullies at treeline. Be aware that a wind slab avalanche may provide enough force to trigger a deeper weak layer.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 2