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Avalanche Forecast

Archived

Feb 21st, 2019–Feb 22nd, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead.

Recent observations of persistent slab avalanches and whumpfing indicate buried weak layers remain touchy. Wind slabs may also exist at higher elevations.

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Clear skies, light to moderate west wind, alpine temperature -14 C.FRIDAY: Cloudy with light snowfall, accumulation 1 to 3 cm, moderate southwest wind, alpine temperature -13 C.SATURDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, light northeast wind, alpine temperature -16 C.SUNDAY: Partly cloudy, light northeast wind, alpine temperature -17 C.

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

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

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.