Avalanche Forecast

Issued: Jan 16th, 2014 8:14AM

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

triley, Avalanche Canada

Kootenay Boundary.

Forecast very warm temperatures are an added concern to a complex snowpack.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Overnight and Friday: A warm and dry airmass I expected to move into the Interior mountains overnight. Expect very warm alpine temperatures with above freezing up to about 3000 metres by the afternoon. Winds should diminish to light Westerly during the day. Clear skies should add strong solar radiation to the already warm air.Saturday: Continued very warm alpine temperatures with light winds and mostly clear skies. Becoming cloudy in the evening and cooling to near freezing.Sunday: Mix of sun and clouds with moderate to strong Westerly winds and freezing levels near 2000 metres.

Avalanche Summary

One natural avalanche size 3.0 was reported from the North of the region that released close to the ground, suspect basal facets. Some natural cornice falls to size 2.0 and explosive control up to size 3.0 near Nelson. The size 3.0 avalanche released down to the weak layer of facets near the ground (Basal facets), and was up to 3 metres deep. Some loose wet avalanches were reported from steep solar aspects to size 1.0 in the highway corridor.

Snowpack Summary

The North of the region received more storm snow over the past week than the rest of the region. The storm slab in the North is close to a metre thick and appears to be more touchy than in most of the rest of the region. The Rossland range has a shallower snowpack and weak basal facets continue to be a concern where wind slabs and storm slabs have added load above the weak layers. The forecast very warm alpine temperatures may result in a period of fairly rapid warming of wind and storm slabs above loose weak layers. Periods of strong solar radiation may cause moist or wet loose snow avalanches and/or cornice falls which may result in large additional loads above deeply buried weak layers.

Problems

Wind Slabs

Recent storm snow has been transported into wind slabs at higher elevations. Some areas may have wind slabs that are about one metre thick. Very warm alpine temperatures may result in loose wet avalanches on southerly aspects, or cornice falls.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Recent storm snow may not be bonding to the surface hoar and melt-freeze crusts that developed before the storm. Storm slabs are more likely in areas sheltered from the recent strong winds. Forecast warm temperatures may result in easier triggering.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar, facet/crust and depth hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Deep Persistent Slabs

This problem is more likely in areas that had a shallow snowpack during the cold arctic outbreak. Loose wet avalanches or cornice falls may trigger deeply buried weak layers resulting in large destructive avalanches.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 17th, 2014 2:00PM