As of Wednesday, Jan. 23
The past week has seen a cool and unsettled period giving us a little teaser of new snow. Periods of strong southerly winds drifted the new snow into lee terrain and did a reasonable job of burying the nasty old rain crust from Jan. 7. The deep layers of the snowpack are currently looking strong and well consolidated, fairly typical for the coast in mid season. However the upper one metre or so is holding a few interesting features which need to be followed as we slide into the current storm cycle.
The recent cold air temperatures set up a steep temperature gradient right across the upper rain crust causing weak faceted crystals to form above and below the crust. Periods of clear overnight skies combined with high humidity also added a weakness in the form of feathery surface hoar crystals, now buried anywhere from 40 to 100 cm deep depending on region.
Few avalanches have occurred on these weak layers but this scenario should change dramatically over the next few days as the loading increases. It should be noted that these weaknesses are present at all elevations including the normally safer below-treeline zones. We are accustomed to safely playing down in the trees while the storm rages in the alpine. While this should still be possible we should be extremely cautious of those surprise open glades, gullies and cut blocks lurking in the timber.
Lots of quick pits and shear tests down to the January crust will be required in order to track stability adequately. It should also be remembered that these weaknesses may not strengthen much after passage of the storm, unlike our more typical new snow instabilities.
Wednesday, through Friday should bring a period of intense snowfall, warmer temperatures and strong southerly winds driving the avalanche danger rating to HIGH for Alpine and treeline zones, CONSIDERABLE below treeline.
A cool and unstable regime will follow for the weekend. This post storm period may prove tricky and a cautious attitude is advised. For a backcountry advisory for areas adjacent to the ski areas call 938 7676. For regions further afield try WWW.AVALANCHE.CA or 1-800-667-1105.
