Archived

Avalanche Forecast

Mar 17th, 2015–Mar 18th, 2015

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

Lingering storm instabilities remain a concern, especially in the alpine. Avoid steep, wind loaded features and large, unsupported slopes. Use extra caution on sun-exposed slopes during the heat of the afternoon.

Confidence

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

Weather Forecast

Light precipitation (2-4mm) can be expected for much of the region Tuesday overnight and Wednesday morning. By Wednesday afternoon the clouds should break and sunny periods are possible. Freezing levels should reach around 2000m Wednesday afternoon and alpine winds should be moderate from the NW. On Thursday, a warm storm system reaches the south coast. There is currently quite a bit of uncertainty regarding the timing and track of the system into the interior regions. For the KB region, it is currently looking like unsettled conditions for Thursday with mainly cloudy conditions and light scattered precipitation. Freezing levels should again reach around 2000m and alpine winds may be moderate or strong from the SW. On Friday, light precipitation is expected but amounts are uncertain. Freezing levels may climb to over 2500m.

Avalanche Summary

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 in the afternoon. On Wednesday, loose wet avalanches are possible during the heat of the afternoon, especially on sun-exposed slopes. Human-triggering of storm slabs remains a major concern, especially in the alpine. Wind-loaded features and steep, unsupported slopes are the most likely areas to trigger an avalanche.

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. The new snow sits on the mid-March rain crust that formed during the rain event on Saturday. The mid-Feb layer was down around 20cm before the rain event and there is currently uncertainty as to the status of this layer. Older deeply buried persistent weak layers still exist in the snowpack. These layers have not been reactive lately but the extremes of warm weather followed by heavy loading from rain and snow make it difficult to assess how the snowpack will respond.

Avalanche Problems

Storm Slabs

20-30cm thick storm slabs sit over a new rain crust. At lower elevations or on sunny slopes, these slabs may be moist or wet. At higher elevations, the slabs should be most reactive in wind loaded areas or on steep, unsupported terrain features.

Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain. >The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Loose Wet

Solar radiation and daytime warming will likely deteriorate the upper snowpack initiating 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.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3