Avalanche Canada ghelgeson, Avalanche Canada

South Coast Inland Avalanche Forecast

Jan 14th, 2020 3:00PM

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

Wednesday's storm snow will begin to hide the damage caused by strong north wind earlier this week. Seeking out sheltered trees will keep you out of wind slab territory and offer the best riding as the first in a series of storms impacts the region.

Summary

Confidence

Low - Uncertainty is due to the extreme variability of wind effect on the snowpack. Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

We’re moving into a period where it’s one storm after the next for the foreseeable future and it should warm up a bit beginning Saturday morning. The storms that are lining up are not particularly juicy, but light snowfall should be pretty consistent.

TUESDAY NIGHT: Moderate to strong west wind, 1 to 8 cm of very light density snow possible.

WEDNESDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong wind generally out of the south, 1 to 5 cm of very light density snow possible during the day with potential for 2 to 10 cm of snow Wednesday night.

THURSDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong southwest wind, 1 to 5 cm of snow possible.

FRIDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong south/southwest wind, 1 to 5 cm of snow possible.

Avalanche Summary

On Monday small wind and storm slabs to size 1.5 were observed in the recent storm snow. Interesting to note that wind slabs were observed in open treeline features which speaks to the tenacity of Sunday's north wind event.

No new avalanche activity to report from Sunday.

On Saturday, the snowpack was reactive to explosive triggers. Some avalanches stepped down to a feathery surface hoar layer buried 50-60 cm deep.

On Thursday explosive control work produced a size 2 avalanche off the Duffey Lake road that released on the mid November facet/crust layer.

Snowpack Summary

On Sunday funky wind out of the N/NE associated with an Arctic Front likely formed fresh wind slabs in locations we aren't used to seeing them. The subsequent cold temperatures should be helping the upper snowpack to settle out quite rapidly.

Previous to Sunday's wind event the riding quality has been phenomenal throughout the region, but there are still some areas for concern deeper in the snowpack:

  • A deep persistent weak layer is at the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). It's made up of sugary faceted grains and a hard melt-freeze crust. This is an atypical setup for this part of the province, it's not going away anytime soon and we should all probably remain a bit wary of big alpine lines, at least for now.
  • There are currently no concerns about deep weaknesses in the snowpack near Coquihalla summit.
  • Most of the region has an unusually thin snowpack in the alpine.
  • Almost no snow is found below about 1500 m.

Terrain and Travel

  • Be aware of highly variable recent wind loading patterns.
  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible

Expected Size

1 - 2

Wednesday's new storm snow will begin to hide wind slabs formed by previously strong winds out of the North which were followed by wind out of the southwest. Cold temperatures have limited the reactivity of these slabs, but they main remain problematic near ridge top, especially in more extreme terrain. 

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

2 - 3

Two layers that cause concern:

  • In many parts of the region, with the exception potentially being near Coquihalla summit, settling storm snow may overly a surface hoar layer found around treeline elevations in sheltered areas. 
  • In the north half of the region, a weak layer is buried near the bottom of the snowpack which continues to produce sporadic very large avalanches.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Jan 15th, 2020 5:00PM