Avalog Join
Archived

Avalanche Forecast

Feb 12th, 2019–Feb 13th, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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.

With great powder comes great responsibility. Expect heavy sluffing with the new snow and recognize that danger has increased when you see signs of slab formation. This will happen more quickly at higher, wind-affected elevations.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tuesday night: Cloudy with continuing periods of snow bringing 10-15 cm of new snow. Light to moderate southwest winds.Wednesday: Decreasing cloud with easing flurries and a trace of new snow, with new snow totals around 40 cm. Light southwest or west winds. Alpine high temperatures around -10.Thursday: A mix of sun and cloud, with cloud increasing and flurries beginning in the evening. Light east winds. Alpine high temperatures around -7.Friday: Cloudy with continuing flurries and a trace to 5 cm of new snow, with new snow totals of around 10 cm. Light southwest winds. Alpine high temperatures around -6.

Avalanche Summary

Preliminary observations from Tuesday showed widespread loose dry and storm slab releases reaching size 1.5. These occurred naturally as well as with ski cutting and skier traffic. Expect a continuation of this type of activity on Wednesday.A report from the Flathead on Monday described continued observations of large whumpfs at 1700-1800 metres. This can be attributed to collapsing of the large, weak, January 17 layer of surface hoar. Collapses of this type on a sufficiently large and steep slopes can be expected to produce persistent slab releases.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. This is the latest of several recent observations of persistent slab avalanches failing on the persistent weak layer that was buried in mid-January. The persistent weak layer producing these avalanches is described in the Snowpack Summary below.

Snowpack Summary

30-50 cm of new snow has buried 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, another 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 60 to 80 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. This layer was the subject of a 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.

Avalanche Problems

Storm Slabs

Up to 50 cm of new snow fell in the Fernie area by end of day Tuesday, with snowfall forecast to continue through Tuesday night. Reactive storm slabs are forming in areas affected by wind and as the new snow settles and consolidates.
Expects widespread instability in the new snow. It will need several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Anticipate more rapid slab formation in overhead terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1 - 2

Loose Dry

Loose snow avalanches are a serious concern for Wednesday with upwards of 50 cm of new snow in the region. Terrain traps and careless group management can greatly increase the consequences of loose dry avalanches.
Sluffs will be easy to trigger in steep terrain that is sheltered from the windGood group management is essential to manage current conditions safely.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Certain

Expected Size: 1 - 2

Persistent Slabs

Snowfall has been increasing the load on a persistent weak layer now at least 50-80 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.
Increase caution around open features from 1600-2000 m, such as cutblocks, gullies, and cutbanks.Choose simple terrain and low-consequence slopes where buried surface hoar may be preserved.Watch for signs of instability such as whumpfing or cracking, especially at treeline and below.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible - Likely

Expected Size: 1.5 - 2.5