Friday January 10, 2020
Deep Persistent Slab, Wind Slab, Storm Slab
Travel & Terrain Advice
Natural Avalanches possible. Human triggered avalanches likely. Stick to lower angled terrain. New snow varies in terms of extent of volume of precipitation across Vancouver Island. Be aware as you move through the terrain for shooting cracks and signs of instability (including new avalanches). Convex unsupported terrain features in leeward (down wind) terrain would be an area to be highly cautious of when navigating through the backcountry this weekend. Allow for an additional 36-48 HRS before stepping onto leeward terrain (downwind) areas particularly if the forecasted precipitation of 30+cm of new snow AND/OR signs of snow transport by strong winds exists in your area. The main issue to keep in mind is that Strong winds will appear from the SE on Friday and create leeward terrain windslabs primed for triggering in specific areas. On Saturday, the winds will shift and come from the NW and also create new pockets of leeward terrain windslabs. Therefore, there is a reasonable likelihood of unstable snow (snow cracking underfoot/under sled)this weekend on multiple aspects at Treeline and Alpine elevation bands, so pick your lines carefully.
No new avalanches reported. Expect stability and avalanche conditions to deteriorate over the course of the weekend given the substantial storm snow and consistent high winds throughout many regions of Vancouver Island throughout the weekend until winds taper off Sunday.
Deep Persistent Slab
There is a surface Hoar layer that has been stubborn but reactive to testing in the field. It remains a potential major hazard (at Treeline and possibly at Alpine elevation bands) for larger scale avalanches (size 2.5) as the Surface Hoar persists it will undergo a major loading event from the forecasted snow on Friday. This Surface Hoar layer has been found on all aspects at Treeline and Alpine elevation bands and in areas where surface hoar has grown while protected from winds. This layer of surface hoar has been very stubborn to initiate however it would be wise to be extremely cautious as there is substantial new “load” acting on the snowpack as a result of storm snow and extreme winds forecasted for Friday and Saturday in specific regions of Vancouver Island.
Major precipitation in the form of snow/load and strong winds in certain areas on Vancouver Island on Friday and Saturday will cause major instabilities in the snowpack on Friday. Expect all Alpine and Treeline environments to be very likely areas to trigger a wind slab avalanche on Friday, Saturday and into Sunday.
Major precipitation in the form of snow/load will cause major instabilities in the snowpack in certain areas on Vancouver Island on Friday and into Saturday and possibly Sunday. Expect all Alpine and Treeline environments to be very likely areas to trigger a storm snow avalanche.
Cold temperatures, a hiatus in precipitation have translated to a snowpack that is consolidating and gaining a good deal of stability. There remains 2 persistent weak layers in the snowpack that could contribute to avalanches. The first layer of concern exists 40cm below the snowpack surface and is a rain/melt freeze crust. This layer is providing results on testing and will remain in the front of our decision making mindset as we travel through avalanche terrain. The 2nd layer of concern is a facet/surface hoar layer, the 2nd persistent weakness in our Vancouver Island snowpack also provides results to testing and for the time being is more stubborn to initiate. The test results on this layer suggest a large amount of stress could be necessary to initiate an avalanche. An example of “large amount of stress” could be multiple sleds or skiers on the slope at the same time or repeated recreation on steeper unsupported terrain in Alpine or High elevation Treeline terrain. Expect these aforementioned layers to be deeper after this weekends storm cycle thoughout many mountainous regions of Vancouver Island.
|Surface||20cm -40 cm of light dry powder that is consolidating|
|Upper||A laminated Rain crust of several ice layers from Friday's major rain event is confirmed from mid island (Mt Wash) to North Island (Mt Cain)|
|Mid||Well bonded midpack that does include two weaker layers (Facet layer and Surface Hoar layer)|
Cold clear temperatures through much of Vancouver Island have allowed for a steady consolidation of the upper snowpack. Everything changes Friday as a new storm cycle hits Vancouver Island bringing with it abundant precipitation and lower freezing levels. SNOW!
A large storm cycle will deposit 30cm-60cm of snow throughout Treeline and Alpine areas of Vancouver Island. Unfortunately, the low pressure system will trigger a major wind event from the South as well during the height of precipitation on Friday. On Saturday the winds will return to the Alpine, this time from the North. As the colder temps settle in, the winds will lessen and decrease to light winds by Sunday from the North.
Friday — 30cm - 60 cm of snow is expected (possibly Rain for Below Treeline elevation) , Extreme Winds will lessen throughout the day but expect more snow transport to multiple aspects as wind direction will move snow from windward terrain onto leeward (downwind) areas. Temps -1 to +0.5 and down again to -2 by early afternoon, Freezing Level rising to 1,100M and dropping to 800M by early afternoon.
Saturday — 1cm to 7 cm of snow, Strong to Moderate Winds throughout the day from the WNW, Temps - 2 to - 10, Freezing Level 700M
Sunday — 1cm to 9cm of snow, Light Winds from the NW, Temps -8 to -17, Freezing Level 200M
Posted on Friday January 10, 2020 by Ryan Shelly