Avalanche Forecast

Issued: Mar 17th, 2022 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs.

Avalanche Canada bchristie, Avalanche Canada

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Start with conservative lines, and check for signs of instability like shooting cracks or recent avalanches before riding in committing features. Avalanche danger is improving, but moderate snowfall and wind continue. 

Summary

Confidence

Moderate - The snowpack structure is generally well understood. Uncertainty is due to limitations in the field data.

Weather Forecast

Unsettled weather continues with light snowfall. Heavier snowfall is forecasted for the immediate coast and further up some inlets, but it is looking unlikely that it will push inland.

THURSDAY NIGHT: Cloudy. 0-3 cm of snow expected. Moderate south ridgetop wind. Freezing level around 600 m. Alpine temperature around -6 °C.

FRIDAY: Mostly cloudy. 0-5 cm of snow expected overnight, with another 0-5 through the day (up to 15 cm around Kitimat). Moderate to strong south ridgetop wind, with periods of extreme in the high alpine. Freezing level around 900 m.

SATURDAY: Partly cloudy. 5 cm of snow expected overnight, and another trace through the day. Freezing level down to 500 m overnight, and rising to 750 m through the day.  

SUNDAY: Partly cloudy. 0-10 cm of snow expected. Light southwest ridgetop winds, trending to strong south in the afternoon. Freezing level at valley bottom overnight, rising to 600 m through the day. 

Avalanche Summary

On Thursday, west of Terrace, where heavier snow and rainfall has continued, small, naturally triggered dry loose avalanches were reported in the high alpine, as well as a large glide slab avalanche at treeline. 

On Wednesday, natural, loose, wet and dry avalanches were reported in steep terrain at low elevations, small storm slab avalanches continued to be rider triggered from just below treeline into the alpine, and the occasional large, naturally triggered storm slab avalanche was reported in large alpine features.

  • One noteable report: northwest of Terrace, a small rider triggered storm slab avalanche was reported on a northeast aspect just below treeline. It was 60 cm deep, and may have failed on a layer of weak, feathery crystals buried in early March. 

On Tuesday, northeast of Terrace, several small natural and rider triggered storm slab avalanches were reported around treeline. East of Terrace, a size 2.5 naturally triggered storm slab avalanche was reported on a southeast aspect. It started around treeline, and kept moving well below treeline. 

Areas north and east of Stewart have generally seen larger, and more numerous avalanches through the recent stormy and unsettled period. 

Snowpack Summary

35-80cm of recent snow has fallen, with strong southwest winds creating deeper deposits on east facing aspects. Low elevations may hold 10-30 cm of wet/moist snow sitting over a widespread crust on all aspects below 1200 m.

Below the recent storm snow, a melt freeze crust exists on south facing slopes, with isolated surface hoar in sheltered terrain features at treeline and alpine elevations. A few operations are tracking surface hoar layers 50-100 cm below the snow surface, but it does not seem to be producing avalanches or concerning snowpack tests.

Another layer of crust and surface hoar sits 60-100 cm deep, buried in late February. It is most prominent in sheltered terrain features at treeline elevations. This layer has shown limited reactivity within the last week. It is more likely to be triggered by large loads like cornice falls or smaller avalanches in motion. 

A thick rain crust from mid-February is buried 100-150 cm. The snowpack below is well consolidated.

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Start with conservative lines and watch for clues of instability.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be careful as you transition into wind affected terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

Expect strong west/southwest winds to build larger slabs in east facing terrain features. 

Storm snow may sit over a crust on south facing terrain features, and/ or a surface hoar layer in sheltered terrain features at treeline and above. 

Reports suggest a layer of buried surface hoar is most widespread in terrain surrounding Terrace. 

Watch and listen for signs of instability, like shooting cracks or whumpfs. 

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Valid until: Mar 18th, 2022 4:00PM