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RegisterDec 10th, 2020–Dec 11th, 2020
Purcells.
Assess for how well recent new snow is sticking to to buried crusts and surface hoar before you commit to steep lines / riding terrain. Watch for pockets of wind slab. Higher hazard lingers to the north where more snowfall was received.
Cooler, with a mix of sun, clouds and snow flurries for the next few days as a high pressure shifts to the east ahead of the next weak low pressure which moves in Sunday.
Thursday Night: Mostly cloudy with broken clear skies, light and variable winds (KH- SE 25), freezing level 600m. Alpine Low -6C.
Friday: A mix of sun and clouds with isolated flurries (Toby shows 4cm) ( light and variable winds, freezing level 800 m. Alpine Low -11C / High -9C
Saturday: A mix of sun and clouds with isolated fluries, light to moderate Westerly winds, freezing level valley botttom. Alpine Low -11C / High -10C (warmer south -9/-7)
Sunday: Cloudy with snow flurries, Trace Accumulations 0-5cm, light-moderate Southwesterly winds, freezing level 700 m. Alpine Low -11C / High -8C
Recent avalanche activity was dependent on snowfall amounts and freezing lines experienced locally during this recent storm. Thus, more activity was reported near Rogers Pass (who received 30-50cm), in the Northern Columbias (who received 40cm) and in the North of the Purcells (who received 15-25cm) than in the south.
On Wednesday, avalanche control work was able to trigger large avalanches on the Nov 5 curs - a deep persistent layer - in northerly shallow rocky terrain near tree line.
On Tuesday, a group found steep wind affected terrain as reported in this MIN along Reudi's Ridge nearby to Kicking Horse.
At or during the height of the storm there were numerous reports large and very large avalanches that ran natural and from avalanche control work. Cooler temperatures and the passing of the storm should result in tapering avalanche hazard.
Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
The combination of a warm storm earlier this week followed by cooler temperatures has reworked the snowpack. As things cool after high freezing levels, anticipate refrozen surfaces below treeline up to 1800m. Freezing rain was also observed at some locations in the southern Purcells to ridge top, but appears to have missed the northern Purcells. New snow is not bonding well to this melt freeze/rain crust, where present.
Recent snow (10-30cm) sits on top of a variety of surfaces: old wind affected terrain, buried melt-freeze crust on south aspects and widespread surface hoar at tree line and below. While high freezing levels may have helped to break down the surface hoar in lower elevation locations, it will still be intact where snow remained cool. In other words, if there are no THICK rain crusts at and below tree line, be on the look out for buried surface hoar.
A recent MIN near Kicking Horse resort describes signs of instability, test results on buried Surface Hoar layers and how they managed terrain to avoid any problems.
The lower snowpack is characterized by a couple of crusts, the most notable is from rains in early November (Nov 5 Crust). This crust is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.