Avalanche Forecast

Issued: Jan 14th, 2018 4:46PM

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

cgarritty, Avalanche Canada

Lizard-Flathead.

The southeast corner of the province is just a step behind interior regions that have seen a sharp increase in large avalanches due to solar input and warming. We're not out of the woods yet.

Summary

Confidence

Moderate -

Weather Forecast

Monday: A mix of sun and cloud with thicker valley cloud due to a developing temperature inversion. Light southeast winds. Freezing level rising to 2500 metres with alpine high temperatures to around 0.Tuesday: A mix of sun and cloud. Moderate to strong southwest winds. Above freezing temperatures developing at all elevations with alpine temperatures dropping from around 0 to -2.Wednesday: A mix of sun and cloud with flurries beginning in the afternoon. Moderate southwest winds. Freezing level to about 1500 metres with alpine high temperatures to around -2.

Avalanche Summary

On Saturday a larger avalanche was triggered with explosives running on the November crust down 100 to 200 cm. This was a size 3.5 slide that ran nearly 800m and exceeded the path's historic runout distance. Other reports from Saturday included observations of explosives control in the Fernie area successfully producing persistent slab releases to Size 2.Â Friday's reports were of intentionally triggered small avalanches on small & low consequence "test slopes", larger (size 2.5 explosive triggered slides) and most interestingly (importantly) remotely triggered avalanches from 20m away.

Snowpack Summary

The snowpack remains near a tipping point. Cooler temperatures Friday and Saturday reduced the sensitivity slightly but forecast warming should bring us back closer to the balance point.Over 100 cm of snow fell within the past week. The snow fell relatively warm with moderate winds, which formed storm slabs and large cornices. This storm snow sits on variable feathery surface hoar in the region. Deeper in the snowpack, an unstable weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found at treeline and below treeline elevations. Below, a rain crust that developed late-November with associated sugary facets are also being stressed. Snowpack test results show sudden fracture characters and high propagation potential for all of these buried layers, indicating that they can be triggered and could propagate into large, destructive avalanches. This has been the case, as shown in the Avalanche Summary.

Problems

Persistent Slabs

Large avalanches are being triggered on a number of buried weak layers, even in fairly dense trees and shallow slope angles, including remotely triggered slides. These layers are touchy and can produce very large, destructive avalanches that run far.

Avoid lingering or regrouping in runout zones.Travel in avalanche terrain is not recommended with current conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Wind Slabs

Variable winds have redistributed loose snow into wind slabs around ridgecrests and exposed terrain features. A small wind slab release may provide enough force to trigger a deeper persistent weak layer.

Use ridges or ribs to avoid pockets of wind loaded snow.Be increasingly cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 15th, 2018 2:00PM