Avalanche Forecast

Issued: Mar 6th, 2019 4:55PM

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

kdevine, Avalanche Canada

South Columbia.

The South Columbia region may receive up to 25 cm of snow by Thursday afternoon. Human triggered avalanches are possible, especially in wind loaded areas, and at lower elevations where buries surface hoar exists.

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 10-20 km/h / alpine low temperature near -10THURSDAY - Mainly cloudy with flurries, 5-10 cm. / southwest winds 10-20 km/h / alpine high temperature near -8FRIDAY - Mainly cloudy with flurries, 3-5 cm / southwest 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

Observations from the past few days have shown size 1-2 wind slabs releasing with skier traffic on a range of aspects in the alpine and at treeline. Small (size 1-1.5) loose dry avalanches have also been observed releasing naturally from steeper, sun exposed slopes. Persistent slab avalanche activity on the mid-January weak layer has slowed down, but not stopped. This layer has evolved a lower likelihood avalanche problem focused at treeline and below. Check out the great photos from a MIN report dated from February 23 for a higher consequence example of this layer's potential. Take note of the low angle terrain, treeline elevation, and the light load of a single ski track that triggered this avalanche.

Snowpack Summary

5-15 cm of snow is expected to fall over Wednesday night and Thursday with mainly light southerly winds. Some convective snow showers on Thursday could mean that some areas receive up to 25 cm.The new snow will likely sit on wind slabs, surface hoar (feathery crystals) and facets (sugary snow), and a crust on sun exposed slopes. The wind slabs may continue to be reactive since they are sitting on facets.There are three prominent weak layers in the upper snowpack that were buried in mid and late January, and early February. They can be found between 30-90 cm below the surface. These layers consist primarily of surface hoar, though they may be associated with crusts on steeper, south facing slopes. These weak layers have been most prominent and most reactive at lower elevations - 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 on. They may become difficult to detect as they get buried by the new snow.

Avoid wind loaded pockets near ridge crests and back off from slopes that feel hollow or drum-like.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Persistent Slabs

Three persistent weak layers are buried between 30-90 cm. These layers have evolved into a lower likelihood/high consequence avalanche problem.

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

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely

Expected Size

1 - 2

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