Avalanche Forecast

Archived

Jan 19th, 2020–Jan 20th, 2020

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Cariboos.

New slabs may be touchy and the warming trend has the potential of waking up the buried weak layer. Travel conservatively during this period of uncertainty.

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

SUNDAY NIGHT: Cloudy with snowfall, accumulation 3 to 10 cm, moderate to strong southwest wind, alpine temperature -2 C, freezing level rising to 1000 m.

MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -3 C, freezing level 1200 m.

TUESDAY: Cloudy with snowfall, accumulation 2 to 5 cm, light to moderate south wind, alpine temperature -5 C, freezing level below valley bottom.

WEDNESDAY: Morning snowfall then a mix of sun and cloud, accumulation 1 to 3 cm, light southwest wind, alpine temperature -7 C, freezing level below valley bottom.

Avalanche Summary

Avalanche activity has quieted down over the past few days, but new snowfall, strong southwest wind, and a rise in air temperature will likely produce new slabs, with the most reactive being in exposed terrain at and above treeline.

There hasn't been an avalanche reported on the persistent slab problem since January 13. The likelihood of triggering this layer could increase as the air temperature rises on Sunday night into Monday.

Snowpack Summary

The south of the region received around 10 to 20 cm of snow on Saturday and another 10 to 20 cm of snow may accumulated Sunday night into Monday. The snow is accompanied by strong southwest wind as well as an increase in the freezing level, meaning that the snow may form cohesive slabs relatively quickly. The touchiest slabs will likely be in lee terrain features at and above treeline.

The main concern over the past couple of weeks has been a layer of surface hoar buried 60 to 120 cm deep. Although an avalanche has not been reported on this layer in the past six days, the likelihood of triggering it may increase as the air temperature warms.

Terrain and Travel

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Extra caution for areas experiencing rapidly warming temperatures for the first time.
Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.