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Avalanche Forecast

Feb 18th, 2019–Feb 19th, 2019
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
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Lizard-Flathead.

Recent observations of persistent slab avalanches indicate buried weak layers are touchy, particularly in openings like cutblocks and gullies. Also use caution at higher elevations, where wind slabs exist on all aspects.

Confidence

High -

Weather Forecast

MONDAY NIGHT: Clear skies, light to moderate northwest wind, alpine temperature -16 C.TUESDAY: Increasing clouds over the day with light afternoon snowfall, trace accumulation, moderate west wind, alpine temperature -15 C.WEDNESDAY: Cloudy with light snowfall, accumulation 5 cm, light to moderate northeast wind, alpine temperature -12 C.THURSDAY: Early-morning snowfall and afternoon clearing, trace accumulation, light to moderate northeast wind, alpine temperature -16 C.

Avalanche Summary

On Monday, small (size 1 to 1.5) wind slab avalanches were triggered naturally and by skiers. They were generally found on westerly aspects in exposed alpine terrain and around 20 to 30 cm deep.On Saturday and Sunday, many persistent slab avalanches were observed. A skier triggered a large (size 2 to 2.5) avalanche within a slide path on a northeast aspect near Fernie. The avalanche was about 40 to 80 cm deep, on a northeast aspect, and at 1700 m. Although speculative, it is suspected that the avalanche may have released on one or both of the weak layers described in the Snowpack Summary. There was also widespread large (size 2) persistent slab avalanches observed - check the report out here and another one here. The avalanches also released on the surface hoar described in the Snowpack Summary. The slabs were 40 to 100 cm deep and occurred between 1550 m and 1700 m on north aspects. There has been substantial further evidence of instability within the buried weak layers, for example in the MIN reports here, here, and here.

Snowpack Summary

Around 20 cm of snow recently fell in the region, which has been redistributed by wind, forming wind slabs in lee terrain features at higher elevations. The wind was first westerly and switched to northeast, so wind slabs may be found on all aspects. In sheltered areas between 1600 and 1800 m, this recent snow may overly a weak layer of surface hoar crystals.Two more weak layers may be found within the snowpack. Surface hoar that was buried early-February may be found about 30 to 50 cm deep in shaded and sheltered areas above 1600 m. The mid-January layer of surface hoar is buried around 80 to 100 cm and is most prominent between 1600 m and 1900 m.The remainder of the snowpack is well-settled. Thin snowpack areas, such as in the far east of the region, may have weak and sugary faceted grains near the base of the snowpack.

Avalanche Problems

Persistent Slabs

Two weak layers of surface hoar may be found between 1500 m and 1900 m, around 40 to 80 cm deep in the snowpack. These layers have been the culprit of recent large avalanches, particularly in openings such as cutblocks, gullies, and slide paths.
Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Make observations and assess conditions continually as you travel.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3

Wind Slabs

The recent snow may continue to be reactive to human traffic. Wind was first from the west and shifted to the northeast, which likely moved the recent snow around at higher elevations. Use particular caution in lee terrain features near ridges.
Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Keep an eye out for reverse loading due to variable winds.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2