Avalanche Forecast

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday

A mild storm track is expected this weekend, which should allow for a bit of a warm up at valley bottom.  FRIDAY:  Overcast, freezing level around 500 m, light to moderate southwest wind, 1 to 3 mm of precipitation expected.SATURDAY:  Overcast, freezing level around 500 m, light to moderate southwest wind, 1 to 4 mm of precipitation expected.SUNDAY:  Overcast, freezing level around 500 m, light west/northwest wind, trace of precipitation expected.

On Thursday we received a preliminary report of an avalanche accident in the Evening Ridge area outside of Nelson.  No details about the size or failure plane are known at this time.On Monday another avalanche failing on the mid-December interface was triggered remotely from 10 m away as a skier approached a rocky outcropping on an east/southeast facing feature around 1900 m, MIN report with photos here. A skier also triggered a small storm slab on a west facing feature around 2200 m Monday which was suspected to have failed on the late December surface hoar. On Sunday a skier was involved in an avalanche on an east facing treeline feature at Kootenay Pass. A recent crown profile has shown that this avalanche failed on the late November crust/facet interface. On Saturday we received two reports of large avalanches failing on the mid-December interface. The first was initiated by explosive control work, the size 2.5 avalanche ran on a 35 to 40 degree slope that was southeast through southwest facing at treeline. The second avalanche was a size 3.0 that released naturally on a 30 degree east facing slope between 1900 and 1400 m. This crown was up to 75 cm in depth.

Last week two successive storms produced 25 to 50 cm of low density storm snow that was accompanied by moderate to strong winds out of the east, southeast, south and southwest. The new snow overlies the late December surface hoar which is 3 to 5 mm in size. We don't know much about the distribution of this weak layer yet. Warming alpine temperatures on Tuesday began to moisten the snow surface on steep southerly aspects. Surface hoar has started to blossom on the surface recently too.Between 60 and 100 cm below the surface you'll find the December 15th interface which consists of a melt-freeze crust on steep, solar, higher elevation slopes and well-developed surface hoar which seems most pronounced in sheltered terrain at and below treeline. The overlying slab is now deep and is gaining cohesion. This interface has hit the tipping point for human triggering as evidenced by recent avalanche activity listed above.Two laminated crusts created by twin rain events in late November lay just below the December 15th interface, 60 to 100 cm below the surface. There may be facets above the uppermost crust and sandwiched between the two crusts.