It's time to back off this weekend as new snow & wind continue to fuel storm slabs that are expected to remain sensitive to both human and natural triggering. Stick to simple avalanche terrain and avoid overhead hazard. Careful in the trees, buried weak layers exist there too.
A weak layer of buried surface hoar may be found in parts of the region. There is uncertainty on where this layer is a problem, but it appears to be of highest concern in sheltered terrain features near treeline. Continued rapid loading of the snowpack could re-activate this interface.
50 to 100 cm of snow has fallen across the region over the later half of the week and there's more snow in store this weekend. Storm slabs have been widespread to size 2 and they could get bigger as the storm continues. A buried surface hoar layer may make storm slabs particularly sensitive to human triggering. Alpine storm slabs could be quite deep and destructive, especially in wind loaded pockets near ridgecrest.
We’re in store for another stormy weekend in the North Rockies.
FRIDAY NIGHT: Freezing level at valley bottom, moderate to strong southwest wind, 15 to 20 cm of snow expected.
SATURDAY: Overcast, freezing level at valley bottom, moderate to strong west/northwest wind, 5 to 15 cm of snow expected.
SUNDAY: Broken cloud cover, freezing level at valley bottom, light to moderate west/northwest wind, 5 to 10 cm of snow expected.
MONDAY: Broken cloud cover, freezing level at valley bottom, moderate west/northwest wind, trace of snow possible.
Throughout the storm there has been a widespread natural avalanche cycle to size 2 within the storm snow. Continued snow and wind are expected to continue to fuel this avalanche cycle.
Wednesday, Thursday and Friday produced 50 (Kakwa) to 100 (Torpy) cm of storm snow under mild temperatures and moderate wind from the south, southwest and southeast. Easy sudden planar shears and wide spread storm slabs have been observed in all of the new snow. The presence of buried surface hoar about 50 cm below the surface has been confirmed in both the Pine Pass and Torpy zones, it may be more widespread throughout the region too.
Below all the recent storm snow there is a thin rain crust from the warm, wet storm on Feb 01. This rain crust has been reported to exist up to treeline elevations around 1700 m. Initially this layer was described as reactive and was the focus of a number of avalanches. With up to a meter of new snow on it it could become active again this weekend.
Deep in the the mid-pack there may still be a layer of surface hoar buried in late December. It's gaining strength, but should remain a concern since snowpack tests still demonstrate this layer has the potential to slide, albeit in isolated areas and/or with very large triggers.
