Avalanche Forecast

Issued: Mar 19th, 2015 9:13AM

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 may be building at higher elevations where there is still dry snow. Continued warm conditions means loose wet avalanches remain a concern during the heat of the afternoon.

Summary

Confidence

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

Weather Forecast

The series of storm pulses that are hitting the south coast are currently missing the KB region as they move through the interior but this should change on Saturday. On Friday, unsettled conditions are expected and light scattered precipitation is possible. Mainly cloudy conditions are expected with the possibility of sunny breaks. Freezing levels are expected to reach around 2500m and alpine winds should be strong from the SW. On Saturday, light precipitation is expected for most of the day and models are currently showing anywhere from 10-25mm. Freezing levels are forecast to progressively drop on Saturday and could be as low as 1500m by the end of precipitation event. This means rain switching to snow at many elevations. Sunday is showing a clearing trend and a mix of sun and cloud is expected with mainly dry conditions.

Avalanche Summary

On Wednesday, loose wet activity was reported from steep rocky sun-exposed slopes. Skiers were also triggering wet sluffs during the heat of the day. 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 Friday, loose wet avalanches are possible during the heat of the day, especially if there is rain or periods of sun. In the alpine, old wind slabs may still be reactive and new wind slabs are expected to be building with the current strong SW winds.

Snowpack Summary

During the heat afternoon of the afternoon, the snow surface has been reported to be moist or wet at all elevations on solar aspects and up to 2000m on north aspects. Melt-freeze cycles are occurring at higher elevations with a weak crust forming overnight and then breaking down during the afternoon. Up to 35cm of snow sits over the mid-March rain crust which is up to 15cm thick. Reports suggest that this recent snow is generally bonding well to the crust. Older deeply buried persistent weak layers still exist in the snowpack but are no longer expected to be reactive.

Problems

Wind Slabs

At higher elevations where the snow is dry, strong SW winds are expected to be forming new wind slabs or adding to the existing slabs.

Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid freshly wind loaded features.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Loose Wet

Daytime warming will weaken the upper snowpack and increase the likelihood of loose wet avalanches. Rain or periods of sun will enhance this effect. Overhead hazards like cornices could also fail and trigger slab avalanches from the slopes below.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 20th, 2015 2:00PM