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Archived

Avalanche Forecast

Jan 13th, 2012–Jan 15th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

Confidence

Fair - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

Friday night: 5-10cm new snow is expected. Saturday:5-10 cm new snow. Treeline temperatures falling to around -13 by the end of the day. Winds moderate to strong westerly. Sunday: flurries or light precipitation. Moderate westerly winds. Temperatures around -10. Monday: Flurries or light precipitation. Temperatures falling to around -15C.

Avalanche Summary

On Thursday a vehicle triggered a size 2 slab avalanche on an E aspect at 2250m. The avalanche slid on a layer of facets buried 60-90cm below the surface. Other recent observations include isolated small human-triggered wind slab and loose snow avalanches near ridgecrests.

Snowpack Summary

Recent light amounts dry snow has maintained the snow supply for fresh wind slab development and cornice growth. Surface condition in wind-exposed areas is highly variable with scoured areas, sastrugi, and pockets of fresh hard and soft wind slabs. Cold temperatures are promoting surface faceting, and a new batch of surface hoar is growing in sheltered areas. A thin melt/freeze crust can be found in the upper snowpack as high as 1900m, and some areas are reporting surface hoar buried early-January now down 10-30cm. The late-December interface is now down 30-60cm and producing moderate to hard resistant snowpack test results. The mid-December surface hoar/facet persistent weakness, down 40-100cm, is generally producing anywhere from easy results where it's shallow to hard results where it's deeper. But recent tests on a north facing treeline slope produced easy results where the surface hoar was found down 70cm, and all tests consistently show a high propensity to propagate fractures. Recent whumpfing suggests basal facets remain concern in shallow snowpack areas especially with heavy triggers in thin spots, and weaknesses in the slab above create the potential for step-down avalanches.

Avalanche Problems

Wind Slabs

Fresh wind slabs are lurking below ridge crests, behind terrain features, and in cross-loaded gullies.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

Weak surface hoar is primarily a concern on big unsupported sheltered glades on east through north aspects. Basal depth hoar and facets are a concern on slopes with shallow and variable snowpack depths, especially near ridges and summits.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 5