Avalanche Forecast

Issued: Feb 24th, 2017 3:44PM

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

triley, Avalanche Canada

Lizard-Flathead.

Changing winds may transport recent storm snow into deep pockets on several aspects.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Tonight: Overcast with light west winds, flurries, and alpine temperatures -15. Saturday: Overcast with light snow and periods of intense flurries. Expect 5-10 cm of new snow combined with moderate westerly winds. Sunday: Overcast with light easterly winds and 3-5 cm of new snow, and alpine temperatures -15. Monday: Overcast with flurries and southerly winds.

Avalanche Summary

Explosives control near Fernie resulted in a deep persistent avalanche on Friday; this avalanche was size 2.5 on a north aspect at 2000 metres, and is believed to have released on the mid-December facets. There was a report on Tuesday of a natural avalanche size 3.5 on Mt Hosmer on an East aspect at 2100 metres that appears to have released on or stepped down to the weak deep persistent layer of sugary facets near the ground. On Wednesday we had a report of a size 3.0 avalanche on "Big Steep Mother" bowl on a northeast aspect at 2100 metres in the alpine in the Lizard range. This avalanche appears to have been started by a cornice fall that released a storm slab that then "stepped down" to deeply buried weak facets.

Snowpack Summary

There is now 50-60 cm of storm snow that is expected to settle into a storm slab. This slab sits above a thick rain crust below 1900 m and a generally well settled snowpack. Isolated basal weaknesses may still exist in shallow snowpack areas. These weak areas appear to be on north-northeast aspects in the alpine. If the winds shift direction over the next few days, watch for new wind loading on south-west aspects.

Problems

Deep Persistent Slabs

There have been two natural deep persistent slab releases in the past few days in the Lizard range. Both of these avalanches were on northeast aspects in the alpine, and released to size 3.0 or larger.

Be aware of the potential for large, deep avalanches.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Storm Slabs

Deep storm slabs (50-60cm) may take some time to settle and bond to the old surface. This problem may linger in areas with a hard rain crust below the storm snow.

Use caution in lee areas. New snowfall mixed with wind loading will create slabs.Minimize exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 25th, 2017 2:00PM