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Avalanche Forecast

Archived

Nov 26th, 2019–Nov 27th, 2019

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

Regions

Purcells.

A cold, windy day is forecast for Wednesday. Wind slabs may overly several weak layers.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

TUESDAY NIGHT: Cloudy with light snowfall, accumulation 2 to 5 cm, light to moderate east wind, alpine temperature -15 C, freezing level below valley bottom.

WEDNESDAY: Mostly cloudy with light snowfall, accumulation 1 to 3 cm, moderate to strong east wind, alpine temperature -17 C, freezing level below valley bottom.

THURSDAY: Clear skies, light northeast wind, alpine temperature -16 C, freezing level below valley bottom.

FRIDAY: Clear skies, light northeast wind, alpine temperature -14 C, freezing level below valley bottom.

Avalanche Summary

We've received reports of a skier and explosives triggering avalanches on north facing alpine terrain in the past few days.

If you see anything while out in the field, please consider sharing that information with us and fellow recreationists via the Mountain Information Network (MIN).

Snowpack Summary

Around 10 to 30 cm of recent snow may overly a weak layer of feathery surface hoar. The distribution of the surface hoar is currently not well understood. The recent snow may get blown around on Wednesday with strong wind from the northeast, forming wind slabs at higher elevations.

Spatial variability is large right now, with the snowpack depth ranging from 10 cm to 100 cm. Expect to find weak and faceted snow in the thin areas. Elsewhere, you may find a potentially problematic melt-freeze crust from late October above faceted snow near the base of the snowpack.

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.