Avalanche Forecast

Issued: Feb 22nd, 2019 6:24PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

jfloyer, Avalanche Canada

Lizard-Flathead.

Forecast updated 0815 Saturday:50-60 cm very low density snow has increased avalanche danger to HIGH in the alpine and in other windy areas. Expect widespread sluffing on steep slopes in more sheltered locations.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is 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.

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. Where snow remains unconsolidated a significant loose dry problem may exist.

If triggered, storm or wind slabs may step down to deeper layers resulting in large avalanches.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 2.5

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.

Be aware of the potential for wide propagation.Watch for signs of instability such as whumpfing, cracking, or recent avalanches.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Feb 23rd, 2019 2:00PM