Conditions are primed for human triggered avalanches at all elevations: There's a buried weak layer in the snowpack, with a critical amount of recent storm snow sitting on top. Conservative terrain choices are key for safe riding this weekend.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Dry with cool temperatures for the foreseeable future. SUNDAY: Mostly sunny. Ridge wind light southwest. Temperature -14. Freezing level surface.MONDAY: Mix of sun and cloud. Ridge wind light southwest. Temperature -12. Freezing level surface.TUESDAY: Mix of sun and cloud. Ridge wind light west. Temperature -12. Freezing level surface.
Avalanche Summary
A widespread natural avalanche cycle occurred on Friday into Saturday producing storm slab avalanches to Size 2 on north through south easterly aspects between 1700 m and 2100 m.A surprising amount of natural avalanche activity was also reported below treeline on Saturday - see
here for the MIN report and details. On Thursday, natural and skier triggered storm slab releases up to size 1.5 were reported including a remote-triggered Size 1.5 slab on an open, rock slope on a north west aspect below treeline. Whumpfing and cracking in rocky areas was also reported on Thursday. See the report on the Mountain Information Network (MIN)
here.Earlier in the week on Monday, one large naturally-triggered avalanche (size 2) was reported on a north-facing alpine feature that likely failed on the mid-December surface hoar layer. There have been some isolated reports of whumpfs and small avalanches failing on the mid-December surface hoar layer, which remains a concern with the on-going storm loading.
Snowpack Summary
Since Thursday, 20-35 cm of storm snow fell on top of 25 cm of previous very low density storm snow. Winds (at times strong from the south west) have modified the snow pack, creating an "upside-down" storm slab layer with stiffer snow on top of softer snow.This upside-down storm snow layer overlies roughly 50 cm of old storm snow from last week that formed into stiff wind slabs in exposed terrain near ridge top, but remains low density in sheltered areas. The mid-December layer is now buried 60-80 cm below the surface. The layer includes crusts on south and west facing slopes and feathery surface hoar in sheltered areas at and below treeline, and has been producing moderate, sudden results in recent snowpack tests.The lower snowpack is generally well settled with a thick prominent crust that was buried near the end of November.
mgrist,
Avalanche Canada
