Avalanche Forecast

Issued: Feb 14th, 2017 3:58PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet, Storm Slabs and Persistent Slabs.

mgrist, Avalanche Canada

Kootenay Boundary.

We're moving into a period of elevated danger: where there is rain, watch out for loose wet ; where there is snow, watch out for storm slabs.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

Warm and wet on Wednesday - Thursday. Cooling with light precipitation on Friday. WEDNESDAY: Rain to treeline (10mm) ; wet heavy snow in the alpine (10-15cm) / Strong southerly winds becoming moderate / Freezing level around 2000m / High temperatures to 0 Celsius. THURSDAY: Wet snow (20-30cm) / Moderate southeasterly winds / Freezing level around 1700 m. FRIDAY: Mostly cloudy with isolated flurries (local amounts to 10cm) / High temperatures to -2 Celsius / Light-moderate southerly winds / Freezing level around 1100 m.

Avalanche Summary

Several loose wet avalanches to Size 2 were reported on steep solar (south) aspects on Monday.Of particular note was a Size 3 natural avalanche on Wolf ridge near Kootenay pass on Monday - the sun's effect is significant! See the great photo in the MIN report (here).

Snowpack Summary

The recent warming and sunny conditions gave us a widespread sun crust on all but high northerly (and some westerly) aspects, where there is still some cold snow to be found. At the end of last week up to 30cm additional snow fell (mostly near Nelson) and brought the recent storm snow total to 65-100cm, creating touchy storm slabs at all upper elevations and aspects. Slabs were reported as very reactive to human triggers and are sitting on a variety of surfaces; including scoured surfaces in wind exposed terrain, surface hoar (size 2-3 mm) in sheltered locations, and sun crust on steep solar aspects.Snowpack tests near the Valhallas have given moderate, propagation-likely results down 50-70cms on the Feb 3rd interface. Areas with a shallower snowpack (less than 150 cm) have a generally weak snowpack structure with sugary facets near the ground. This includes shallow alpine slopes and most of the Rossland range. It is possible for storm slab avalanches to step-down to these deeper weak layers, resulting in large, destructive avalanches.

Problems

Loose Wet

Where the precipitation falls as rain, watch out for loose wet where the snow is soft and cohesionless. Avoid getting pushed into terrain features like gullies and cliffs, where even small slides could have large consequences.

Avoid lingering in runout zones.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Storm Slabs

The last storm started cold and ended warm, creating a dangerous condition where warmer heavy snow is sitting on-top colder snow. Wind effect also made slab avalanches much more likely.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Use small slopes with low consequence to test the bond of the storm snow.Watch for signs of instability such as whumpfing, shotting cracks, or recent natural avalanching.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Storm slabs may step-down to deeper weak layers, resulting in large, destructive avalanches.

Wait to see how the snowpack responds to increased loads before venturing out into bigger terrainAvoid likely trigger spots such as steep and rocky areas with a shallow snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 15th, 2017 2:00PM