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Archived

Avalanche Forecast

Feb 22nd, 2019–Feb 23rd, 2019
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
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
2: Moderate
The avalanche danger rating at treeline will be moderate
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Lizard-Flathead.

Snowfall observations were far exceeding forecast amounts on Friday afternoon in the Fernie area. Treat the danger as CONSIDERABLE if you encounter 25 cm of new snow or more on Saturday.

Confidence

Low - Forecast snowfall amounts are uncertain

Weather Forecast

Friday night: Cloudy with flurries bringing 5-10 cm of  new snow, with a possibility of enhanced low density amounts of 20 cm or more. Light to moderate southwest winds.Saturday: Mainly cloudy with easing isolated flurries and a trace of new snow. Light to moderate northeast winds. Alpine high temperatures around -15.Sunday: Sunny with cloudy periods. Light northeast winds. Alpine high temperatures around -20.Monday: Cloudy with sunny periods. Light to moderate northeast winds increasing over the day. Alpine high temperatures around -17.

Avalanche Summary

An explosive triggered a large (size 2.5) persistent slab avalanche on Thursday. It was on a southerly aspect and between 1650 and 2000 m. The slab was about 40 cm deep.Last weekend, many persistent slab avalanches were observed. A skier triggered a large (size 2 to 2.5) avalanche within a slide path near Fernie. The avalanche was about 40 to 80 cm deep, on a northeast aspect, and at 1700 m. The South Rockies field team attended the site on Tuesday and confirmed that the avalanche failed on a layer of surface hoar, check out their report here. Also on Sunday a group of skiers remotely triggered a size 2 avalanche in the Little Sand area at 1650 m, as seen here. Cutblock-type terrain in the Rolling Hills has also been the source of persistent slab avalanches, see here.

Snowpack Summary

Light new snow amounts have buried mainly wind affected surfaces at alpine and treeline elevations, with snowfall forecast to continue through Friday night. In sheltered areas, the new snow is burying faceted surface snow and in some areas a new layer of surface hoar. Wind slabs exist in open, exposed areas at higher elevations. They may be found on all aspects due to variable wind directions. In sheltered areas between 1600 and 1800 m, 20 cm of recent snow may sit on a weak layer of surface hoar crystals buried around Valentines Day in some locations.Two more weak layers of surface hoar 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 70 to 100 cm and is most prominent between 1600 m and 1900 m.The remainder of the snowpack is well-settled.

Avalanche Problems

Storm Slabs

Reported high snowfall rates in the Fernie area means that enough snow may fall by Saturday morning to have formed a widespread new storm slab problem. Areas that see only light new amounts will instead see new wind slabs focused on northeast aspects
Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, storm or wind slabs may step down to deeper layers resulting in large avalanches.Gather information about new snow's depth and its bond to the old surface as you travel.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

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

Expected Size: 2 - 3