Avalanche Forecast

Issued: Mar 15th, 2022 4:00PM

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

Avalanche Canada bchristie, Avalanche Canada

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Sticking to simple, mellow terrain is an easy way to avoid the avalanche problems during this storm. If you venture into small, steeper slopes, watch for signs of instability like shooting cracks, whumpfs, or slushy snow. 

Summary

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system. The snowpack structure is generally well understood.

Weather Forecast

TUESDAY NIGHT: Cloudy. 5-15 cm of snow expected. Moderate southwest ridgetop wind. Freezing level around 900 m. Alpine temperature around -5 °C.

WEDNESDAY: Cloudy. 0-5 cm of snow expected, with up to 20 cm possible around KItimat. Moderate to strong south ridgetop wind, trending to extreme southwest in the high alpine. Freezing level around 900 m. Alpine temperature around -5 °C.

THURSDAY: Partly cloudy. 10-20 cm of snow expected overnight, with another 3-7 cm through the day. Moderate to strong southwest ridgetop wind. Freezing level around 900 m.

FRIDAY: Mostly cloudy. 0-5 cm of snow expected overnight, with another 5-15 through the day. Moderate to strong south ridgetop wind. Freezing level down to around 500 m overnight, back up to 1000 m by the afternoon.

Avalanche Summary

On Tuesday, 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. 

On Monday, east of Terrace, a size 3 naturally triggered avalanche was reported in steep terrain on a north aspect. Northeast of Stewart, several naturally triggered windslab avalanches up to size 3.5 were reported in steep, lee features at treeline and above. Also, numerous loose wet avalanches up to size 1.5 were reported below treeline across the region.

On Sunday, storm and wind slabs were natural and human triggered to size 1.5. Several larger avalanches have been reported where storm slabs sit on a buried surface hoar or crust. 

Activity on deeper persistent weak layers has been limited throughout last weekend's storm. Avalanches are unlikely to be human triggered on these layers, but possible with a large trigger such as a storm slab in motion or a large cornice fall.

Snowpack Summary

50-70cm of recent snow has fallen, with strong southwest winds creating deeper deposits on east facing aspects. Low elevations may hold 10-20 cm of wet/moist snow sitting over a widespread crust on all aspects below 1000 m.

Below the recent storm snow, a melt freeze crust exists on south facing slopes, with surface hoar in sheltered terrain features at treeline and alpine elevations. This has been reactive to human triggers within the last 3 days. Reports suggest the surface hoar is most widespread around Terrace.

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 70-110 cm. The snowpack below is well consolidated.

Terrain and Travel

  • Minimize exposure during periods of heavy loading from new snow, wind or rain.
  • As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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

Likely - Very Likely

Expected Size

2 - 3

Loose Wet

An icon showing Loose Wet

Lower elevations will again see snow and/or rain. Avalanches are likely where the surface snow is wet, or where rain breaks down a surface crust. 

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 16th, 2022 4:00PM