Avalanche Forecast

Issued: Mar 6th, 2019 4:31PM

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

kdevine, Avalanche Canada

North Columbia.

Convective snow showers may bring higher than forecast snowfall amounts to some areas. In areas that receive 20 cm or more, consider the danger rating to be MODERATE at all elevation bands.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Convective snow showers on Thursday could mean that some areas receive higher than forecast snowfall amounts.WEDNESDAY NIGHT - Mainly cloudy with flurries, up to 5 cm / southeast winds 10-30 km/h / alpine low temperature near -9THURSDAY - Mainly cloudy with flurries, 5 cm. / southwest winds 15-30 km/h / alpine high temperature near -8FRIDAY - Mainly cloudy with flurries, 3-5 cm / west winds 10-30 km/h / alpine high temperature near -10SATURDAY - A mix of sun and cloud / northwest winds, 10-20 km/h / alpine high temperature near -10

Avalanche Summary

On Tuesday there was one size 1 human triggered persistent slab avalanche reported on a north aspect at 1100 m. It failed on the late January persistent weak layer, 40 cm deep and was triggered remotely (from a distance).Generally speaking, reports from the past week are mainly of wind slabs reacting to ski cuts, with a trend toward smaller (size 1) releases. Small (size 1-1.5) loose dry avalanches have also been observed releasing naturally from steeper, sun exposed slopes in recent days.Reports of human triggered persistent slab avalanches on the January weak layers have been on the decline, suggesting these layers have evolved into a lower likelihood/high consequence avalanche problem.

Snowpack Summary

5-10 cm of new snow is expected to fall over Wednesday night and into Thursday. Some convective snow showers could mean that some areas see up to 20 cm.The new snow will sit on wind slabs and facets (sugary snow) and a crust on sun exposed slopes. The wind slabs are also sitting on facets and they may continue to be reactive. There are a two prominent weak layers in the upper snowpack that were buried in mid and late January. These can be found approximately 40-80 cm deep. Both layers consist of surface hoar (feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most reactive at lower elevations, and especially below treeline.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.

Problems

Wind Slabs

Wind slabs can be found on all aspects, and continue to be reactive due to the weak, faceted snow they sit above. They may become difficult to detect with the new snow on top of them.

Exercise increased caution around wind loaded pockets near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Persistent Slabs

Two persistent weak layers are buried approximately 40 cm and 80 cm. These layers have evolved into a lower likelihood avalanche problem that still demands slope assessment and diligent group management at lower elevations.

Exercise increased caution around low elevation cut-blocks where this layer has been well preserved.Maintain diligent group management around open and/or sparsely treed slopes at treeline and below.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely

Expected Size

1 - 2

Valid until: Mar 7th, 2019 2:00PM