South Coast

How long it will take the new snow to stabilize is hard to guess, and the high likelihood of triggering a large avalanche is a dangerous gamble. Stay alert to the potential for blue-sky powder-fever to lure you into consequential terrain.

Sunday ushers in Dr. Jekyll's benign weather following Mr. Hyde's Saturday storm

Saturday night: Decreasing cloudiness, scattered flurries with trace accumulations above 500 m, moderate west winds decreasing to light, treeline temperatures cooling from -1 C to -3 C, freezing level dropping to 500 m.

Sunday: Clearing in the afternoon, isolated flurries with trace accumulations, winds becoming east and light, high treeline temperatures near -3 C, freezing level around 500 m.

Monday: Mainly sunny, no precipitation expected, light variable winds, high treeline temperatures near-1 C, freezing level around 100 m.

Tuesday: Increasing cloudiness, no precipitation expected, winds becoming west and increasing to moderate, high treeline temperatures near 0 C with freezing level rising to 1000 m. 

Though there have been no reports of avalanche activity, we expect a natural cycle occurred during the storm. Although natural avalanche activity is tapering, avalanche conditions are primed for human-triggering on Sunday.

In the neighbouring Sea-to-Sky region on Thursday, we received reports of two large (size 2-3) human-triggered avalanches that released on a persistent weak layer between 1700-1900 m on west and southwest aspects. Notably, these avalanches were remote-triggered while party members were traveling uphill. Several small sympathetic avalanches were also thought to have released during these events. We have concern that this problem may extend into the south coast region at upper elevations in the north of region, such as near Sky Pilot. It may be possible to trigger very large avalanches in isolated areas on Sunday.

Saturday's powerful storm brought 40-70 cm of snow to the mountains. Gradual warming that peaked midday likely created a thin crust over much of the storm snow in areas below 1100 m. A rise in temperature and strong southwest winds likely accelerated and compounded slab formation. Storm slabs may be poorly bonded to previous snow surfaces, which include cold snow, a sun-crust on steep south-facing slopes, and surface hoar reported at treeline elevations and below. Stay alert to changing slab conditions as you move into wind-exposed terrain, and monitor the bond of the new snow to the old snow surface. 

A concerning layer of facets (sugary snow) can be found down 110-180cm over a crust that formed in early December. This video, filmed prior to Saturday's storm, provides a valuable visual summary of these conditions. It may be possible to human trigger this persistent slab problem in thinner snowpack areas near ridge tops, where the facets are more developed and where the crust layers are more accessible to the weight of a person or machine. You can find additional details and photos in our forecaster blog. 

Below these crust layers, the snowpack is generally well-settled. Early season hazards such as rocks, stumps, and open creeks remain at lower elevations. 

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Closely monitor how the new snow is bonding to the old surface.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Remote triggering is a concern, avoid terrain where triggering slopes from below is possible
• Be careful to keep storm day fever from luring you out into bigger terrain features.