Avalanche Forecast

TUESDAY NIGHT: Clear skies, light wind from the northwest, treeline temperatures around -10 C.

WEDNESDAY: Clear skies in the morning with increasing cloud in the afternoon, light wind from the southwest, treeline temperatures warming to -5 C.

THURSDAY: Moderate snowfall with 5-15 cm of new snow, strong wind from the southwest, treeline temperatures warming to -3 C with freezing level reaching 1000 m.

FRIDAY: Mostly sunny, light to moderate wind from the northwest, treeline temperatures around -2 C.

A notable natural avalanche cycle occurred on Monday. Numerous very large (size 3) avalanches were reported in the Selkirks east of Revelstoke (including neighbouring Glacier National Park). These layers occurred at all aspects and elevations and involved both storm slab and deep persistent slab avalanches. The remaining parts of the region did not experience the same level of widespread large avalanches, but there were still many size 1-2 storm slabs across the region and a few reports of large deep persistent slab avalanches in Central Kootenays and Monashees. 

Most of the deep persistent slab avalanches occurred at below treeline elevations (1700 - 2000 m), with many of them triggered by smaller storm slab avalanches starting at higher elevations. These avalanches have typically been 100-150 cm deep and occurred on northeast to northwest aspects.

20-30 cm of recent snow has likely been redistributed into leeward terrain at upper elevations. The amount of new snow is greater in northern parts of the region (e.g. near Revelstoke) than southern parts (e.g. near Nelson).

The upper snowpack contains a complex mix of crusts and small surface hoar layers. We are uncertain about where the most reactive layers may exist, but have noticed the following trends:

• A thin breakable rain crust is buried 10-40 cm deep and is found into the alpine in the most parts of the region except east of Revelstoke where it only extends up to 1800 m.
• A surface hoar layer is buried 20-60 cm deep and has been reactive in some sheltered terrain at treeline and below, particularly around Glacier National Park.
• A suspect layer of facets formed during cold weather at the end of December is 60-90 cm deep, but has not been reactive recently.

While none of these may be obvious widespread weaknesses, the combination and complexity require careful travel in avalanche terrain.

The one widespread weak layer in the Columbias is a more deeply buried crust/facet layer that formed in early December. It is typically down 80-140 cm, but as deep as 200 cm in wind loaded terrain. There has been regular avalanche activity on this layer at all elevations for over a month, and we expect to see continued sporadic very large avalanches.

• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Carefully monitor the bond between the new snow and old surface.
• Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
• Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
• Be aware of the potential for large avalanches due to the presence of buried weak layers.