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Avalanche Forecast

Archived

Dec 18th, 2021–Dec 19th, 2021

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

Regions

Waterton Lakes.

30 cm of unconsolidated snow is being redistributed by strong SW winds. Use caution in lees.

Weather Forecast

Sunday: Mix of Sun and cloud. Light west winds. Alpine temps high -10. Freezing levels valley bottom

Monday: Cloudy with isolated flurries. Moderate south west winds. Alpine temps high -9. Freezing levels valley bottom.

Tuesday: Cloudy with isolated flurries. Strong west winds. Alpine temps high -5. Freezing levels valley bottom.

Snowpack Summary

30 cm of unconsolidated snow is being redistributed by moderate gusting to extreme SW winds. This overlies a 20-40cm buried windslab ALP/TL atop 10cm of facet above the Dec 4 rain crust. A 20-60 cm thick Nov melt freeze crust complex completes the snowpack to ground. BTL has just reached threshold in some places. Snow depth at TL is 100 - 170.

Avalanche Summary

No new avalanches reported. Field observations limited due to visibility. If you go out into the mountains please share your observations on the Mountain Information Network.

Confidence

Forecast snowfall amounts are uncertain on Saturday

Problems

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.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.