Wind will be the main driver of avalanche hazard on Tuesday. Watch for drifted areas with stiffer snow and avoid exposure to cornices.
Recent snow accumulations ranging from 5-15 cm are being redistributed by variable winds into wind slabs on lee features at upper elevations. Given the variability in wind direction, anticipate wind slabs across a wide range of aspects. Ongoing wind and snow over the past week have contributed to cornice growth. Cornice falls may trigger avalanches on the slopes below.
The likelihood of triggering a weak layer of surface hoar buried Jan 11 buried 40-60 cm deep is decreasing, but it may still persist on sheltered, open slopes near treeline. This persistent slab problem is a low likelihood/high consequence event, and there is uncertainty as to its distribution and sensitivity to triggering across the region. Deeper layers from early December and November can still be found in the snowpack and remain a cause for concern in thick to thin areas at upper elevations.
Monday night: Mostly clear, light northwest winds, alpine temperatures near -14 C.
Tuesday: Partly cloud, winds shifting to the southwest and increasing to strong, alpine high temperatures near -10 C.
Wednesday: Partly cloudy, overnight flurries with trace accumulations, light northwest winds, alpine high temperatures near -12 C.
Thursday: Mainly sunny, light northeast winds, alpine high temperatures near -14 C.
No recent avalanches have been observed. Strong winds on Tuesday are expected to continue to build wind slabs that may be possible to human trigger. Cornices may be reaching their breaking point and can act as triggers on slopes below.
Avalanches breaking in the recent snow have the potential to step down to deeper layers, creating larger and more destructive avalanches. This MIN report from the Quartz zone on Thursday shows the reactive layer of Jan 11th surface hoar on north-facing slopes near treeline. There is uncertainty as to how quickly this weak layer will transition to unreactive across the region.
In the aftermath of the storm last Tuesday, we received reports of avalanches reaching size 3 in the central part of the region, lending support to the idea that some larger releases may have involved more deeply buried persistent weak layers. Although avalanche activity on these layers from early December and November has been isolated, the possibility exists for large triggers to reactivate these deeper instabilities.
Incremental accumulations over the weekend varied across the region, with 10 cm falling in the north near Quartz Creek and Toby Creek and with up to 5 cm in the south near Kimberley. Winds have switched direction from the south to the northwest, creating a tricky reverse-loading pattern at upper elevations. Winds are forecast to shift back to the southwest and to increase on Tuesday, making wind slabs on lee features at upper elevations the primary concern. Ongoing snow and wind have contributed to notable cornice growth.
30-60 cm of snow from the past week has buried a Jan 11th weak of layer of surface hoar. This persistent weak layer is most suspect in sheltered, open slopes at treeline. Snowpack tests suggest the likelihood of triggering this layer is decreasing.
Two deeper layers of surface hoar from December 13th and December 7th may still be found down 100-150 cm. The Dec 7th weak layer consists of a combination of decomposing surface hoar with a crust and faceted snow. Avalanche activity on these persistent weak layers has dwindled in the last week, with snowpack tests results trending to resistant and unreactive.
The lower snowpack is characterized by a notable rain crust from early November that is surrounded by a weak layer of sugary facets. It may still be possible to trigger with large loads in steep, shallow, rocky areas with a thin to thick snowpack.
