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Avalanche Forecast

Archived

Mar 14th, 2021–Mar 15th, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

The snowpack will need time to stabilize after the recent intense storm. Storm and wind slabs will be reactive to skiers and riders. Be cautious and watch for signs of instability like whumpfing, hollow sounds, shooting cracks and recent avalanche activity.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

SUNDAY NIGHT: Clear, 30 km/h northwest wind, alpine low -17 C. 

MONDAY: Cloudy, up to 5 cm new snow, 30 km/h southwest wind, alpine high -5 C.

TUESDAY: Cloudy, 10 to 15 cm new snow, 60 km/h southerly wind, alpine high 1 C, freezing level rising to 1000 m.

WEDNESDAY: Mix of sun and cloud, 10 to 15 cm new snow, 60 km/h south wind, alpine high 1 C, freezing level at 1000 m.

Avalanche Summary

A widespread natural avalanche cycle with storm slab avalanches up to size 4 started on Friday morning and continued into Saturday. Explosives triggered storm slab avalanches of size 2 to 3 in the entire region. A natural persistent slab avalanche of size 3.5 was observed east of Kitimat. Numerous wet slab avalanches up to size 3 and wet loose avalanches of size 1 to 2 were observed as well as several glide snow avalanches up to size 2.5.

Several natural glide snow avalanches and loose wet avalanches up to size 2 were reported on Wednesday. Some avalanche activity was observed on southerly aspects on Tuesday during the heat of the day. A few cornices were also triggered, which did not trigger slabs on the slopes below.

Snowpack Summary

The recent storm brought up to 150 cm snow in the south of the region and about 50 cm in the north. The precipitation was combined with moderate to strong southerly wind and fell as rain below 900 m saturating the upper snowpack. The new snow may overly feathery surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects and below treeline.

Around 100 to 300 cm overlies a persistent weak layer buried in mid-February that may still be a concern in parts of the region. The layer consists of feathery surface hoar crystals in areas sheltered from the wind and sugary faceted grains that formed during February's cold snap. Avalanche activity on this layer has mostly occurred west of Terrace along Highway 16 and in the Kitimat area in the past week, but the layer could still be of concern anywhere it exists.

There are currently no layers of concern in the mid and lower snowpack.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.