Avalanche Forecast

Issued: Feb 10th, 2017 4:54PM

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

Avalanche Canada cgarritty, Avalanche Canada

A Special Public Avalanche Warning applies to this region. Don't let your guard down yet. A combo of recent snow, strong winds, and rising temperatures will keep avalanche danger elevated through the weekend.

Summary

Confidence

Moderate - Freezing levels are uncertain on Sunday

Weather Forecast

Friday night: Flurries bringing up to 5 cm of new snow. Winds extreme from the southwest.Saturday: A mix of sun and cloud. Winds strong from the west. Freezing level rising 700 metres with alpine temperatures of -11.Sunday: Mainly cloudy. Winds strong from the southwest. Freezing level rising to 800 metres with alpine temperatures of -5. Possibility of freezing level rising to 2000 metres with alpine temperatures above freezing.Monday: Cloudy with sunny periods. Winds light from the southwest. Freezing level rising to 1700 metres, possibly as high as 2500 metres, with alpine temperatures to -1 or possibly well above 0.

Avalanche Summary

On Thursday there was a report of a Size 2.5 natural avalanche 50-120cm deep on a NW aspect in Waterton Park. Nearby on the east slope of the Rockies, a Size 2.5 wind slab was brought down with explosives, leaving behind a 40-100cm crown fracture. Expect the recent dense storm slab to remain reactive to human triggering in the coming days as the all the new snow from the past 10 days starts to settle. Storm slab avalanches have the potential to step down to the basal weakness which would drastically increase the size and destructive potential of a resulting avalanche.

Snowpack Summary

15-30cm of moist new snow fell over the region on Thursday, with some periods of rain observed at lower elevations. This precipitation has accumulated above the 90cm of low density storm snow that we received last weekend. Strong shifting winds have redistributed the previous storm's snow in exposed terrain forming touchy wind slabs. These wind slabs are now obscured by the latest blanket of snow. All of this overlies a highly variable old surface which may include wind affected surfaces, facets, and/or a rain crust below around 1500 m. Recent reports suggest a poor bond between the storms' snow and the old surface. In deeper areas, the snowpack appears to be well settled with isolated concerns about the mid-December facet layer which was buried 50-100 cm deep prior to the weekend storm. In shallow snowpack areas and at lower elevations, the snowpack is weak, faceted, and has no structure. Prior to the storm, it was possible to step onto the snow surface in these areas and sink right to the ground.

Problems

Storm Slabs

An icon showing Storm Slabs
Additional new snow, warmer temperatures, and strong winds have created touchy new storm and wind slabs
Use conservative route selection, choose low angled and supported terrain with low consequence.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A weak layer at the bottom of the snowpack is creating the potential for full depth avalanche releases. Storm slab avalanches have the potential to step down to this layer. This is most likely in the thin snowpack areas of the region.
Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.If triggered the storm slabs may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 11th, 2017 2:00PM