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Archived

Avalanche Forecast

Jan 4th, 2019–Jan 5th, 2019
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Kootenay Boundary.

Storm slabs have formed with recent snowfall and winds. Expect deeper and more reactive deposits in wind-loaded terrain.

Confidence

Low - Due to the number of field observations

Weather Forecast

FRIDAY NIGHT: Cloudy with flurries, trace to 5 cm snow. Moderate to light southwest wind. Freezing level dropping below 500mSATURDAY: Cloudy with isolated flurries, trace to 5 cm snow. Moderate increasing strong south wind. Freezing level rising to 1400 m.SUNDAY: Flurries, 5-15 cm snow. Moderate west wind with occasional strong gusts. Freezing level 1000 m.MONDAY: Scattered cloud and isolated flurries, snowfall starting late Monday night. Light west wind with occasional moderate gusts. Freezing level below 500 m.

Avalanche Summary

On Friday, explosives triggered storm slab avalanches to size 2.5 and one natural size 1.5 avalanche was reported. These avalanches occurred on north aspects with crowns up to 60 cm.During the day Thursday, storm slab avalanches to size 2 failed naturally and were triggered by explosives. Storm snow was reactive to skier traffic with shooting cracks up to 20 m. Visibility was poor and limited observations were reported.

Snowpack Summary

15-20 cm recent snow accumulation has been redistributed by winds forming slabs in lee features and scouring exposed terrain. A zipper crust within the storm snow resulting from a freezing mist is most likely found at elevations below 2100 m.Below the storm snow, several layers of small spotty surface hoar and thin crusts have been observed in the top 50-70 cm of the snowpack. Some snowpack tests suggest the snow may be poorly bonded to these layers in isolated areas. However, the main weak layer worth considering is still the widespread weak layer that formed in early December. The layer consists of a rain crust with a weak layer of feathery surface hoar and sugary facets and can be found 70 to 100 cm below the surface. Although there has not been a reported avalanche on this layer in over a week, a large load like a cornice falling could be enough to reawaken it.

Avalanche Problems

Storm Slabs

New snow is being redistributed by wind, loading lee features and scouring more exposed terrain. Expect deeper and more reactive deposits of snow in wind load areas.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1.5 - 2.5