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Avalanche Forecast

Archived

Feb 20th, 2021–Feb 21st, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Widespread avalanches certain.
Treeline
Widespread avalanches certain.
Below Treeline
Widespread avalanches certain.

Regions

Glacier.

New snow will not bond well to the complex drought interface of old facetted surfaces and previous windslabs.

Hazard levels will continue to increase as the storm intensifies through the weekend; peaking Sunday night into Monday morning.

Weather Forecast

A westerly flow is over BC, bringing a series of fronts Saturday night through Monday.

Today: Cloudy with flurries (5cm). Alpine High -10 C. Ridge wind strong W.

Tonight: Flurries (5 cm). Low -11 C. Strong SW wind.

Sunday: Snow (20-30cm). High -5 C. Extreme SW wind. Freezing level (FZL) 1300m.

Monday: Snow (15-20cm). Extreme W wind. FZL 1300m.

Snowpack Summary

Up to 15cm of snow overnight, brings the total to 20-40cm over the Feb. 14th drought interface; this is predominantly a wind crust in exposed areas near the height of the pass, and buried windslabs and facets as you move East and West. Facets, and a waek suncrust still linger down ~70cm at the Jan. 24th PWL. The mid and lower snowpack are strong.

Avalanche Summary

Field teams observed small avalanches recently in the Illecillewaet (size 1.5 windslab low in the Dogleg) and Flat creek (size 1.0 dry loose from a NW aspect in the alpine).

There has been more snowfall just to our West, and avalanche activity in this area has increased in the past 24hrs - likely a sign of things to come in our region.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.

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.