snowpack summary in revelstoke

The surface hoar war,
face down the bright white places--
Fifteen degrees best.

The recent avalanche accident on Boulder Mountain near the town of Revelstoke has drawn international attention to this year’s snowpack stratigraphy in the Selkirks and Monashees. The Canadian Avalanche Center has issued special warnings regarding avalanche danger for the last three weekends.

The El Nino climactic conditions have set the stage for one of the more volatile layering structures in many people’s memory The combination of higher temps with warmer snow events interspersed with long periods of clear weather have laid down a series of significant buried surface hoar layers. Surface hoar is that beautiful sparkly crystal that forms on the snow surface following cold clear nights(different from depth hoar). If it gets buried it can create an unstable layer in the pack. As of this writing there are four main interfaces which have been named based on the day they were buried. The March 7th, The February 24th, the February 8th and the January 24th. These layers can all be found within about a meter and a half of the snows surface and as such are very reactive to skier triggering. Generally this structure is widespread throughout the treeline and alpine elevations with North through East aspects being the most sensitive. Solar aspects have a series of crusts at the same interfaces and have been waking up as radiation intensifies.

The most recent storm event on March 11th-and 12th came in with significant wind and precipitation increasing load and forming slabs over the existing surface hoar sandwich(actually more like a multi layer torte). The result has been a widespread avalanche cycle with slides initiating on layers closer to the surface and stepping down to deeper layers. This was the set up for the Boulder Mountain accident.

The take home message here is that it is not the time to get complacent if you choose to venture out. Numerous natural, human triggered, and remotely triggered(means you can trigger an adjacent steep slope from low angle terrain – sometimes from quite a distance- and sometimes from below…) avalanches are being reported daily throughout the range. Guiding operations are sticking to terrain that has been heavily skied all winter and to very low angle low consequence terrain with no overhead hazard.

This is a great time to hone your avalanche skills. Instead of focusing on skiing the big line, dig a pit in a safe location and see if you can id all the layers. You will be impressed! For current avalanche bulletins, go to www.avalanche.ca. For field reports from certified guides check out the public mountain conditions report or MCR at www.acmg.ca.