More new snow = touchy new avalanche problems. A localized storm over Wednesday night is expected to keep avalanche conditions in the region especially lively through Thursday. Expect any sustained solar exposure to quickly initiate natural avalanche activity.
A localized storm is expected to rapidly form a fresh storm slab problem in this region over Wednesday night. Large storm slab or wind slab avalanches may also be capable of stepping down or fracturing at more deeply buried storm interfaces to create larger, more destructive avalanches.
Surface snow will destabilize and may avalanche naturally with daytime warming and especially solar exposure.
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth.
Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
A serious avalanche incident occurred in the backcountry just east of Revelstoke on Wednesday. Details are available here.
Otherwise, reports from Monday and Tuesday included many more storm slab and wind slab avalanches, several that were noted for being triggered remotely (from a distance) and a significant number of avalanches attributed to the problematic late-March and early April failure planes discussed in our snowpack summary, now buried under the full depth of recent snowfall. The presence of surface hoar and facets in particular has been noted in some of the more prominent reports of touchy conditions from the past few days.
At least one deeper persistent slab was observed with a 100 cm crown fracture in the western Purcells.
Saturday and Sunday saw an overall increase in wind slab and storm slab activity as the storm touched down in the region. This MIN gives a good sense of the conditions initially at play.
Looking forward, further loading of new snow through Wednesday night will maintain active avalanche conditions for Thursday, with new storm and wind slabs likely, slightly deeper persistent interfaces still in question, and wet loose or even wet slab potential ramping up with daytime warming.
This region is expected to receive a localized storm late in the day/evening Wednesday with accumulations of 20-30 cm.
A later pulse of the early week storm brought a variable trace to 30 cm of new snow to the region Tuesday night. In most areas below 2000 m these recent accumulations overlie a rain crust that formed mid-storm. At higher elevations it brought dry storm snow accumulations to totals around 30-60 cm (and counting).
All this snow overlies either a widespread melt-freeze crust buried April 7, a weak interface of faceted snow and surface hoar buried at the end of March, or some combination of the two. As surface instabilities settle out, both of these interfaces remain in question with numerous recent avalanches attributed to each and with the snowpack still adjusting to the load.
The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Wednesday night
Mainly cloudy with a localized storm bringing 20-30 cm of new snow. Light to moderate northwest winds.
Thursday
Mainly sunny. Light west or southwest winds increasing in late afternoon. Treeline high temperatures around -1 with freezing levels to 1400-1600 m.
Friday
Cloudy with isolated flurries bringing a trace to 5 cm of new snow. Light southwest winds. Treeline high temperatures around 0 with freezing levels to around 1700 m.
Saturday
Becoming cloudy. Light to moderate south winds increasing over the day and evening. Treeline high temperatures around 0 with freezing levels to 1800 m.
More details can be found in the Mountain Weather Forecast.
