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Avalanche Forecast

Archived

Apr 5th, 2017–Apr 6th, 2017

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Observations from the region are becoming limited. If you are out in the mountains, please consider posting your observations to the Mountain Information Network and help us improve the bulletin. Click here for more details.

Confidence

Low - Due to the number of field observations

Weather Forecast

THURSDAY: Flurries or rain showers, accumulation 5-10cm / Moderate south wind / Alpine temperature 1 / Freezing level 2000mFRIDAY: Flurries, accumulation 10cm / Moderate to strong south wind / Alpine temperature 1 / Freezing level 2000mSATURDAY: Flurries, accumulation 5cm / Moderate southwest wind / Alpine temperature -4 / Freezing level 1300m

Avalanche Summary

On Thursday, the main concern is lingering wind slabs in high elevation north facing terrain and the possibility of large overhanging cornices releasing with overall warm temperatures over the coming days.

Snowpack Summary

The region is expected to have entered a period of widespread melt-freeze conditions on all aspects and elevations except for high north facing terrain where the surface snow is expected to remain dry. In high elevation terrain, recent strong southwest winds and new snowfall has formed wind slabs in leeward features. At lower elevations and on sun exposed slopes, there are likely several well bonded crust layers in the upper snowpack. A rain crust which was buried on March 21 extends into the alpine is now down 60-80 cm. This crust was the bed surface for several avalanches during the solar cycle at the end of last week. At elevations above around 2100m, the February persistent weak layers may still be lingering down around 100-150cm and weak basal facets may still be lingering in shallow snowpack areas. These deep weak layers appear to have gone dormant but an isolated avalanche or cornice fall still has the potential to step down in the right conditions.

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.

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.