Avalanche Forecast

Issued: Dec 20th, 2013 8:31AM

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

Avalanche Canada bcorrigan, Avalanche Canada

The avalanche hazard could bump up a notch if more snow than expected arrives.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Saturday: Mainly cloudy with a chance of flurries and sunny breaks. The freezing level could jump to 700 m and moderate gusty northwest winds continue. Sunday: Possible sunny breaks and flurries. The freezing level could climb to 1500 m  in parts of the forecast area. The upper flow continues to be northwesterly. Monday:  5 to 10 cm of snow at upper elevations,  freezing level to remain at valley bottom for most of the area.

Avalanche Summary

No avalanches have been reported in the last few days.

Snowpack Summary

It's been an exceptionally dry December so far. The total monthly precipitation in Nelson is 40 mm, and 30 mm of that fell in one storm at the beginning of the month. Hopefully the weather pattern changes soon!Recent light snowfall and strong westerly winds formed pockets of soft wind slab on lee slopes and scoured windward slopes in exposed terrain. Between 35 and 50cm below the surface you may find a weak layer of surface hoar on sheltered slopes or a melt-freeze crust on steep solar aspects. Most reports indicate this layer is "stubborn" to trigger, or there may not be a deep enough overlying slab to create a significant hazard. That said, I'd remain curious about this interface, especially as the snow load above gradually increases.In general, snowpack depths are below seasonal average and many slopes below treeline are reported to be below threshold for avalanche activity. Deeper snow is likely in the northern part of the region.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong westerly winds at ridge tops have produced pockets of dense wind slab in exposed lee terrain and cross-loaded features. Rider triggering is possible, particularly in steep unsupported terrain.
Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Make observations and assess conditions continually as you travel.>Whumpfing is direct evidence of a buried instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 21st, 2013 2:00PM

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