Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Kootenay Boundary.
Touchy conditions persist in the wake of Sunday night's big dump of snow. The combination of more new snow, strong winds and a buried weak layer are a recipe for elevated danger ratings.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Another significant storm arrives Tuesday into Wednesday, delivering another big wallop of precipitation. Fasten your seat belts folks!TUESDAY: Snow. Accumulation 15-20 cm during the day with another 15-20cm overnight. Ridge wind moderate from the southeast. Temperature near -6. Freezing level 500 m. WEDNESDAY: Cloudy with lingering flurries. Ridge wind moderate northerly. Freezing level at the surface.THURSDAY: Cloudy with isolated flurries. Accumulation of 5-10 cm possible. Ridge wind moderate from the west. Temperature near -7. Freezing level at the surface.
Avalanche Summary
On Monday, numerous storm slabs up to Size 2 were reported in the Nelson area: They were either easily triggered by skiers or ran naturally. Also on Monday, several classic signs of instability (whumphing, shooting cracks, easy sudden results in snowpack tests) were reported near Nelson. See here for the great MIN report.
Snowpack Summary
The Nelson area and points farther south saw 20-30 cm of new snow in Sunday night's storm, with moderate to strong winds. Snow drifts as deep as 60cm have been reported and we also received word that the upper snow pack is 'upside down' (heavier, denser snow on top of lighter snow).All this new snow has fallen on a variety of old snow surfaces, depending on aspect and elevation. On solar aspects a thin melt-freeze crust has been buried. On northerly aspects, feathery, surface hoar crystals (10-60 mm in length) have been buried below treeline as well as protected areas at treeline. In the alpine the old surface consisted of sugary snow (facets) and hard, wind scoured snow. Below the crust layer the lower snowpack is moist and well settled.
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.