Avalanche Forecast

Issued: Mar 26th, 2021 4:00PM

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

Avalanche Canada kdevine, Avalanche Canada

Email

A juicy storm is expected to deliver heavy snow with strong winds to the Northwest Coast. Travel in avalanche terrain is not recommended.

Summary

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

FRIDAY NIGHT - Snow, 15-20 cm / strong west wind / alpine low temperature near -2 / freezing level 1000 m 

SATURDAY - Snow, 25-35 cm, with another 10-20 overnight / extreme southwest wind / alpine high temperature near -2 / freezing level 1000 m 

SUNDAY - A mix of sun and cloud with scattered flurries / moderate northwest wind / alpine high temperature near -5 / freezing level 800 m 

MONDAY - Cloudy with sunny periods and scattered flurries / strong northwest wind / alpine high temperature near -5 / freezing level 800 m

Avalanche Summary

Natural avalanche activity is expected to be widespread throughout the day on Saturday with heavy snow and strong winds in the forecast.

On Thursday, Explosive control work conducted east of Kitimat resulted in cornices failures up to size 2.5, and wind slabs limited to size 1. Dry loose avalanches were also observed up to size 1.5. Around Ningunsaw, there were explosive-triggered avalanches up to size 3, including one that is suspected to have failed on the mid-February persistent weak layer.

Tuesday's storm resulted in a widespread natural avalanche cycle, with size 2-3 storm slab avalanches at upper elevations, and size 1-1.5 wet loose avalanches below treeline.

Several size 2-3 natural glide slab avalanches have been reported over the last week. Avoid slopes with glide cracks on them at all times. They are inherently unstable and can release at any time.

Snowpack Summary

15-20 cm is expected on Friday night, with another 25-35 during the day on Saturday. Storm slabs are expected to be widespread and reactive at upper elevations. Below treeline may see heavy rainfall associated with this storm.

A crust is now buried 75-100 cm below the surface on solar aspects and below 1400 m. At higher elevations where this crust tapers out, the new snow has added significant load to a couple of deeply buried weak layers that we haven't quite ruled out as problems.

The first and most concerning persistent weak layer was buried in mid-March and is around 100-140 cm deep. It consists of surface hoar on sheltered northerly aspects around treeline. 

Down between 150 to 300 cm is another layer of surface hoar and facets, buried in mid-February. This layer may still be a concern in shallower snowpack areas. 

There is a chance that further loading during the incoming storm could result in some large persistent slab avalanches.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Storm slab size and sensitivity to triggering will likely increase through the day.

Problems

Storm Slabs

An icon showing Storm Slabs

Natural avalanches are expected to be widespread with the arrival of the forecast weather.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1.5 - 2.5

Loose Wet

An icon showing Loose Wet

Wet loose avalanches are likely at lower elevations where it is raining.

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Valid until: Mar 27th, 2021 4:00PM