Avalanche Forecast

Issued: Feb 28th, 2019 4:05PM

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.

jsmith, Avalanche Canada

South Columbia.

Recently formed wind slabs are sitting on top of buried wind slabs that are sitting on facets (weak, sugary snow). The fresh wind slabs may still be touchy and the buried wind slabs are remaining reactive to human triggers longer than is typical.

Summary

Confidence

High - The weather pattern is stable

Weather Forecast

THURSDAY NIGHT: Cloudy with isolated flurries; 0-3 cm. / Light, northwesterly winds / Alpine low -13.FRIDAY: Cloudy with isolated flurries; 0-3 cm. / Light, northwesterly winds / Alpine high -11.SATURDAY: Sunny / Light, northeasterly winds / Alpine high -17.SUNDAY: Sunny / Light, northeasterly winds / Alpine high -14.

Avalanche Summary

On Wednesday, a few rider triggered wind slab avalanches up to size 2, on primarily northerly aspects at treeline and above were reported.Persistent slab avalanche activity on the mid-January weak layer has slowed down, but not stopped. This layer has created a low likelihood, high consequence scenario in the snowpack primary at lower elevations. Check out the great photos from a recent MIN. Take note of the low angle terrain and the light load of a single ski track that triggered this avalanche.

Snowpack Summary

Strong northeasterly ridge-top winds have created fresh wind slabs on lee features at treeline and above. Additionally, there are buried wind slabs on a variety of aspects that are sitting on facets (sugary snow) which may cause them to remain reactive to human triggers longer than what is typical for a wind slab problem in this region.There are two prominent weak layers in the upper snowpack. One was buried at the end of January, and the other mid-January. They are approximately 40- 60 cm and 60-90 cm below the surface. Both layers consist of surface hoar (weak, feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most recently reactive at lower elevations 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

Buried, hard wind slabs that often become unreactive after a few days continue to surprise riders. Thin to thick rocky areas are likely places to trigger these.

Avoid wind loaded pockets, especially near ridge crests and roll-overs.Steep and rocky terrain are likely places to trigger buried wind slabs.Avoid slopes that sound hollow or drum-like.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Reports of persistent slab avalanches are becoming less frequent which is creating a low likelihood, high consequence scenario in the snowpack which requires discipline and careful terrain selection to manage effectively.

Avoid steep, open and/or sparsely treed slopes at and below treeline.Avoid low elevation cut-blocks where this layer is well preserved.Use conservative route selection; choose moderate angled terrain with low consequence.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 2.5

Valid until: Mar 1st, 2019 2:00PM