Douglas Island Avalanche Forecast

The most recent observations of avalanche activity on 01/13 in Dan Moller bowl with widespread activity and easily triggered from above and some were remotely triggered from below on flat terrain.

Recent heavy snowfall and winds have come together to give us omnipresent storm slabs!

Storm Slabs develop when fresh snow compacts over a less stable layer or boundary. This weak layer might consist of snow from early in the storm or a poorly adhered interface with the older snow surface. It’s akin to a chain, where the weakest link in a layer of snow formed during a single storm or extended snowy period becomes vulnerable. Storm Slabs often occur when there is minimal or no wind.

Storm Slabs can be challenging to identify because the surface snow often remains soft and powdery. When the new snow has sufficient cohesion, these slabs can trigger shooting cracks and subtle collapses at the junction of the new and old snow layers. Traditional snowpack tests that apply downward pressure (like Compression Tests) are of limited use here, as they often penetrate through both storm slabs and underlying weak layers without effectively pinpointing the issue. Instead, indicators such as tilt tests, ski cuts on small, less consequential slopes, or signs of natural activity on certain slopes offer more reliable clues to the presence of Storm Slabs.

Dealing with and avoiding Storm Slabs is crucial. They pose the greatest risk when they funnel into terrain traps such as forests, gullies, cliffs, or areas where escape routes are limited. Given the soft, low-density nature of these slabs, riders might not immediately recognize when they fail, often underestimating their potential for propagation. Consequently, resulting avalanches can be larger than anticipated. To mitigate the risk, it’s advisable to wait at least a day or two after a storm before venturing into steep avalanche terrain. Typically, Storm Slabs stabilize within a week, so waiting several days after significant snow loading events can significantly reduce exposure to this hazard.

The high winds and heavy snowfall have produced wind slabs that you will likely find on all leeward slopes. A lot of snow has been transported and I would expect these slabs to be fairly deep.

Wind slabs form when wind transports snow from upwind terrain features (windward side) and deposits it on the downwind side (leeward side), creating a cohesive layer. These slabs are typically found on the lee sides of ridgelines, in cross-loaded gullies, and around terrain features such as cliff bands. Wind slabs can vary in hardness and thickness, often appearing smooth and rounded, sometimes described as “pillow-like”, with some sounding hollow. They are most reactive during or shortly after wind events and can persist for days, especially when they overlay weak layers like surface hoar or facets, potentially developing into more dangerous Persistent Slabs. It will be interesting to see how this problem reacts in the coming days/weeks.

Wind slabs are generally confined to specific locations based on wind direction and speed, and are most dangerous right after formation, though they typically stabilize within a week. Recognizing and avoiding wind-loaded terrain, especially in the days following a wind event, is key to managing the risk they pose. Staying in sheltered or wind-scoured areas can also help avoid encountering wind slabs altogether.