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Avalanche Forecast

Feb 9th, 2019–Feb 10th, 2019
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Lizard-Flathead.

Check out the AvCan South Rockies blog for advice on managing the persistent slab problem affecting the region. (Link Here)A Special Public Avalanche Warning is in effect in this region.

Confidence

Moderate -

Weather Forecast

Cold, dry, arctic air continues to dominate the weather pattern for the foreseeable future.SATURDAY NIGHT: Freezing level at valley bottom, around -25 C in the alpine, light variable northerly wind at valley bottom, light southerly wind at ridgetop, no significant snowfall expected.SUNDAY: Clear skies at dawn with cloud cover beginning to increase around lunch, freezing level at valley bottom, around -20 C in the alpine, light southerly wind at all elevations, no significant snowfall expectedMONDAY: Scattered cloud cover, freezing level at valley bottom, around -15 C in the alpine, light southwest wind at valley bottom, moderate southwest wind at ridgetop, no significant snowfall expected. A few centimeters of snow possible Monday night.TUESDAY: Scattered cloud cover, freezing level at valley bottom, around -15 C in the alpine, light variable wind at most elevations with moderate to strong southwest wind at ridgetop, a few cm of snow possible.

Avalanche Summary

A couple of smaller (size 1-1.5) slabs were ski cut on east aspects at 1700-1800 metres in the Fernie area over the past two 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 currently driving 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.The past few days have also produced reports of wind slabs reacting to ski cutting and to explosives in the Fernie area. Sizes ranged from 1-2 and results have been focused on northeast to northwest aspects.

Snowpack Summary

Around 60 mm of precipitation fell last Friday. Above 1600 m, this produced 30-40 cm of new snow which has since been redistributed by strong winds from both north and south. It may sit on weak and feathery surface hoar crystals in shaded and sheltered areas. Below 1600 m, the precipitation fell mainly as rain and formed a new melt-freeze crust on the surface.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 is the subject of our 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.

Avalanche Problems

Wind Slabs

Recent snow above 1600 m has been redistributed by southwest winds that switched to northeast. Deposits in the lee of wind-exposed terrain features may remain reactive to human triggering, particularly near ridges.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

The recent storm brought a critical load to a persistent weak layer now 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