Avalanche Forecast

Issued: Jan 17th, 2021 4:00PM

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

Avalanche Canada dsaly, Avalanche Canada

A quick pause before the stormy trend returns late Monday. Avalanche hazard will remain elevated through this dynamic weather period.

Summary

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

SUNDAY NIGHT- Flurries, 5-10 cm / southwest wind, 30-60 km/h / alpine high temperature near -2 / freezing level 1000 m in the south, near valley bottom in the north

MONDAY - Cloudy with flurries, snowfall increasing later in the day / increasing southwest wind, 30-60 km/h / alpine high temperature near -1 / freezing level rising to 1200 m in the south and closer to the coast, near valley bottom in the north

TUESDAY - Snow starting late Monday, 20-30 cm / west wind, 50-90 km/h / alpine high temperature near -2 / freezing level dropping to valley bottom

WEDNESDAY - Cloudy with isolated flurries / northwest wind, 20-30 km/h / alpine high temperature near -4 / freezing level valley bottom

Avalanche Summary

A quick break in the weather may expose a recent natural avalanche cycle before another dump of precipitation. Continued stormy weather will mean that storm slabs are anticipated to be widespread and natural avalanches are expected.

Several natural small wet-loose avalanches were observed Sunday morning in steep, unsupported terrain near valley bottom. Wet-loose avalanches will remain possible with warm temperatures.

A natural avalanche cycle occurred Thursday into Friday, large (size 2-3) storm slab avalanches were reported along highway corridors. The largest (size 3) avalanches were observed in wind-loaded start zones in the alpine and treeline, but also included below tree line avalanches to size 2 failing on unsupported features. Wet-loose avalanches to size 1.5 were reported from steep rocky slabs below tree line.

There were a few natural avalanches up to size 3 reported in the north of the region on Wednesday. There was also one remotely triggered size 3 persistent slab avalanche reported in the north of the region.

There was a natural avalanche cycle reported on Tuesday, additionally explosives triggered numerous avalanches up to size 2.5 and people triggered a few size 1 avalanches.

Last Monday, there were reports of widespread natural and explosives triggered avalanches up to size 3. The largest avalanches were reported in the north of the region where there has been more recent snow. The avalanches being reported closer to Terrace were generally in the size 1-2 range.

Snowpack Summary

Storm snow totals range around 60-100 cm since January 13, with 20-50 cm fresh, lower-density snow over older, more settled storm snow. Southerly winds have formed deep deposits in lee terrain and mild temperatures have encouraged settlement. Below 800 m rain on snow produced a moist and upside down snowpack, a wet-loose problem will persist with warm temperatures.

In the Shames area, a weak layer of surface hoar has been reported in sheltered areas down around 120-180 cm. 

A bit further north in the Nass/Sterling/Beaupre areas, there is potentially still concern about an older weak layer overlying a crust that is now roughly 180-200 cm deep. And in the far north of the region, there is concern about weak snow at the bottom of the snowpack.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid avalanche terrain during periods of heavy rain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

Ongoing snowfall and flurries continue to drive the ongoing storm slab hazard. Increasing wind and rising freezing levels through Monday will further shake the snowpack and elevate hazard. Expect slabs to be widespread and reactive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet

Warm temperatures will moisten the snowpack and a present wet-loose hazard. Avoid steep slopes and terrain traps at low elevations where the snow is wet.

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Persistent Slabs

An icon showing Persistent Slabs

There are a few different persistent weak layers being reported throughout the region. They are all generally buried between 100-200 cm and tend to consist of either surface hoar or crusts with faceted snow sitting on them.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 18th, 2021 4:00PM