Avalanche Forecast

Archived

Feb 2nd, 2012–Feb 3rd, 2012

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Kootenay Boundary.

Confidence

Good - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

There is a band of warm air at higher elevations that may keep temperatures in the alpine quite warm overnight; probably about -3.0 at 2500 metres. Clear skies should allow the valleys to get slightly below freezing. Friday is expected to be warm with light winds and mostly sunny skies. Valley fog may persist in some areas. Temperatures should drop to near freezing in the valley bottoms overnight. The ridge of high pressure is expected to continue on Saturday, bringing slightly cooler temperatures. Mostly clear skies may produce intense solar radiation during the day on Saturday. Sunday is expected to be mostly clear with light winds and freezing levels up to about 1400 metres.

Avalanche Summary

Reports of loose dry sloughing in steep terrain from several operators in the area up to size 1.5. Explosive control at Kootenay Pass produced several avalanches size 2.5-3.0 on cross loaded slopes with crowns between 50-100 cm.

Snowpack Summary

Another 10-15 cm of snow fell during the day on Wednesday, adding to the recent storm snow. The recent storm snow layer is about 30-50 cm thick and is quite variable across the region. There are a couple of thin crusts buried below the storm snow that have been producing moderate to hard shears in tests. Some areas are still getting sudden planar shears on the mid-december surface hoar layer. The forecast warming trend may weaken the bond on the mid-december layer; particular concern in low snowpack areas.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.