Avalanche Forecast

Issued: Mar 18th, 2015 9:50AM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

Wind slabs are expected to be lingering on north aspect slopes in the alpine. Daytime warming and rain may destabilize the upper snowpack at lower elevations.

Summary

Confidence

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

Weather Forecast

Weak storm pulses will affect the region for the next three days. On Thursday, increasing cloudiness is expected during the day and light precipitation is expected to start Thursday afternoon or evening. Alpine winds will become moderate-to-strong from the SW to W by the afternoon and freezing levels should reach around 2000m. The region can expect 2-5mm Thursday overnight. On Friday, mostly cloudy conditions are expected and lingering flurries are possible. Freezing levels are expected to climb to around 2500m and alpine winds are forecast to be moderate from the SW. On Saturday, the most substantial pulse of precipitation is expected and models are currently showing 5-10mm for the region. The track of the storm is currently to the north of the region and amounts could increase if the storm shifts further south.

Avalanche Summary

On Tuesday, natural loose wet avalanches to size 2 were reported. Skier-triggered avalanches up to size 1.5 were also reported. These occurred on all aspects and elevations, and were reported to have released on the mid-March crust. On Monday, a natural size 2 avalanche was reported from a steep wind-loaded slope, ski cuts produced several size 1 soft storm slabs, and a skier triggered a size 1.5 storm slab. Lots of natural loose wet avalanches up to size 2 were reported from all aspects on Monday afternoon. On Thursday, loose wet avalanches are possible during afternoon, especially if the rain starts early. Human-triggering of wind slabs in the alpine remains the main concern. This problem is probably isolated to high elevation north aspects.

Snowpack Summary

Heavy rain on Saturday soaked the snowpack up to ridge tops. On Sunday, heavy snowfall (up to 35cm) and southwest winds developed new storm slabs that are still reactive to human-triggering in wind loaded areas. The new snow sits on the mid-March rain crust (up to 15cm thick) and reports suggest that the new snow is generally bonding well to the crust. The new snow has become moist on all sun exposed aspects but remains dry on north aspects. Older deeply buried persistent weak layers still exist in the snowpack but are no longer expected to be reactive.

Problems

Wind Slabs

Lingering wind slabs may still be a concern in the alpine on northerly aspects where the snow remains dry. Use extra caution as you move into wind affected terrain.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Loose Wet

Daytime warming and rain will likely deteriorate the upper snowpack and may initiate loose wet avalanches. Overhead hazards like cornices could also fail and trigger slab avalanches on the slopes below.

Be alert to conditions that change with aspect, elevation and time of day.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 19th, 2015 2:00PM