Avalanche Forecast

Archived

Feb 23rd, 2019–Feb 24th, 2019

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary.

Use extra caution on slopes getting hit by the sun, slabs avalanches are possible to trigger at all elevations.

Confidence

High -

Weather Forecast

SATURDAY NIGHT: Cloudy with isolated flurries and trace accumulations, light wind, alpine temperatures drop to -15 C.SUNDAY: Sunny with cloudy periods, light northeast wind, alpine high temperatures around -12 C.MONDAY: Mix of sun and cloud, light northeast wind, alpine high temperatures around -14 C.TUESDAY: Cloudy with scattered flurries and localized accumulations of 5 cm, moderate southeast wind, alpine high temperatures around -14 C.

Avalanche Summary

Preliminary reports from Saturday indicate more small (size 1) avalanches were triggered in the latest storm snow. On Friday, numerous small (size 1) storm slab avalanches were triggered by riders in steep terrain.Human triggered avalanches were reported everyday between February 12 and 20. Although most avalanches were small (size 1-1.5), some have shown impressive propagation on buried weak layers (see some examples here and here). On Tuesday, a notable size 3 persistent slab avalanche occurred on an east aspect at 2000 m. This avalanche was triggered by explosives and failed on the persistent weak layer that was buried on February 7th.

Snowpack Summary

The latest storm has brought 15-25 cm of low density snow that now covers variable wind slabs at higher elevations and sun crusts on south-facing slopes. Fresh wind slabs may be forming in exposed terrain.A weak layer of surface hoar (feathery crystals) and a crust that was buried on February 7th is now 30-50 cm deep. This layer has been reactive, and has produced avalanches as large as size 3. Two other surface hoar layers are buried 50 to 80 cm deep the snowpack (referred to as the February 1st and mid-January layers). Although they have not been reactive recently, they are still being monitored by professionals. These layers are most prevalent below treeline on shady aspects. The lower snowpack is considered generally strong.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.