Avalanche Forecast Lizard Range and Flathead

Date Issued: Valid Until:

Avalanche Canada cgarritty, Avalanche Canada

Avalanche Forecast

Mon Feb. 11th ยท 4:52PM

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Considerable
Storm Slabs Storm Slabs
Persistent Slabs Persistent Slabs

Alpine

Danger Ratings High

Treeline

Danger Ratings High

Below Treeline

Danger Ratings Considerable

Alpine

Danger Ratings Considerable

Treeline

Danger Ratings Considerable

Below Treeline

Danger Ratings Moderate
The pieces are in place for a significant 'Fernie Effect' snowfall event to impact the region. Avalanche danger will increase over the day as new snow accumulates and is affected by wind.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Monday night: Becoming cloudy with flurries beginning with a trace of new snow. Light southwest winds, increasing to strong in the alpine.Tuesday: Cloudy with periods of snow bringing 20-30 cm of new snow, decreasing overnight. Light southwest winds, increasing to strong in the alpine. Alpine high temperatures around -12Wednesday: A mix of sun and cloud with continuing isolated flurries and a trace of new snow, with new snow totals of up to 50 cm. Light west winds. Alpine high temperatures around -8.Thursday: Mainly cloudy with isolated flurries and a trace of new snow. Light southeast winds switching to southwest in the evening. Alpine high temperatures around -7.

Avalanche Summary

Another small (size 1) persistent slab was triggered by a skier in the western Flathead on Saturday. The slab was 40 cm deep and released from a northeast aspect at 1800 metres in an area that had not seen recent traffic. Several other small persistent slabs were triggered with ski cuts in the same area.Smaller (size 1-1.5) slabs were ski cut on east aspects at 1700-1800 metres in the Fernie area over the past few days. These slabs were 40 cm deep and described as storm slabs, failing at our most recent new snow interface. Strategies for avoiding this storm slab problem mirror those for avoiding the persistent slab problem that drove our Special Public Avalanche Warning.A 50 cm-deep size 1.5 persistent slab was triggered with a ski cut on Monday. This occurred on a north aspect at 1720 metres in the Fernie area. This is the latest of several recent observations of persistent slab avalanches failing on the persistent weak layer that was buried in mid-January. It was more widely reactive during and immediately after the storm this past weekend. The persistent weak layer producing these avalanches is described in the Snowpack Summary below.

Snowpack Summary

Light new snow amounts have begun to bury a variable surface of older wind-affected snow at wind-exposed treeline and alpine elevations, a new weak layer of feathery surface hoar in protected areas at lower elevations, and a thick melt-freeze crust below 1600 metres. Below the new snow, 20-40 cm of snow from last weekend's storm may sit on weak and feathery surface hoar crystals in shaded and sheltered areas.Above 1600 metres, the mid-January layer of surface hoar and/or crust is now buried around 40 to 60 cm deep. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m. The melt-freeze crust is found on south aspects at all elevations. Slabs that exist above a combination of surface hoar and crust are likely to be particularly reactive. This layer was the subject of our recent Special Public Avalanche Warning.The remainder of the snowpack is generally well-settled. Thin snowpack areas, such as in the east of the region, may hold weak and sugary faceted grains near the base of the snowpack.

Problems

Storm Slabs

Storm Slabs

New snow will be accumulating Monday night and over the day on Tuesday. It has the potential to quickly form reactive storm slabs in areas affected by wind. Loose dry avalanches will be an increasing concern as snow accumulates in sheltered areas.

If triggered, storm slabs may step down to deeper layers and result in large avalanches.Avoid wind loaded pockets near ridge crests and roll-overs.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Likely

Expected Size

1 - 2
Persistent Slabs

Persistent Slabs

New snow will be increasing the load on a persistent weak layer already buried 30-70 cm deep. This layer consists of surface hoar preserved in shaded, sheltered areas between 1600-2000 m. It may coexist with a crusty sliding surface on south aspects.

Watch for signs of instability such as whumpfing or cracking, especially at treeline and below.Choose simple terrain and low-consequence slopes where buried surface hoar may be preserved.Increase caution around open features from 1600-2000 m, such as cutblocks, gullies, and cutbanks.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5