Wednesday January 8, 2020
Wet Slab, Deep Persistent Slab, Wind Slab, Storm Slab
Travel & Terrain Advice
Wednesday and Thursday are likely the best days to get out explore terrain. On Friday Rain Below Treeline and over 1 foot of new snow at Treeline and Alpine elevation bands is forecast to fall in many parts of the island. As incoming strong rates of precipitation arrive Friday, so too will additional load and stress to the snowpack. ON Friday, dial back your objectives in terms of slope angle and keep an eye out for snow cracking underfoot, whumpfing and other signs of instability. For these reasons, mitigate exposure to steep unsupported terrain. Utilize slopes that have dense vegetation (trees) if you are keen on a steeper descent (particularly on Friday).
No new avalanches to report. Please submit to the Mountain Information Network at Avalanche.ca. This helps the forecaster on duty to better a better sense of localized avalanche conditions.
Friday’s forecast of snow and rain will also exacerbate stability and further stress the snowpack. New snow and rain fall Friday could create dense moisture laden upper snowpack primed for triggering.
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 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 rain and 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 rain, storm snow and extreme winds forecasted for Friday.
Major precipitation in the form of snow/load and strong winds will cause major instabilities in the snowpack on Friday. Expect all Alpine and Treeline environments to be very likely areas to a wind slab avalanche on Friday.
Major precipitation in the form of snow/load will cause major instabilities in the snowpack on Friday. Expect all Alpine and Treeline environments to be very likely areas to a storm snow avalanche.
Cold temperatures, a lessening of precipitation and wind means the snowpack is undergoing a needed phase of consolidation. Bigger objectives are possible at this time however 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.
|Surface||10cm - 30 cm of light, fluffy dry snow and is slowly bonding to rain crust below|
|Upper||thick 10cm melt freeze crust|
|Mid||A well consolidated mid pack that includes a facet and Surface Hoar Layer approximately 60cm down is gradually bonding and less reactive to testing|
Several storm snow events have subsided and colder air temperatures and light winds are facilitating a consolidation process in the snowpack.
Cold and calm weather in the forecast until Friday when a large storm cycle of strong precipitation, and a brief wind and freezing level fluctuation is expected.
Wednesday- Air temps will remain below zero, (1cm-2cm of snow) , Moderate to light mountain top Winds from the West, Temps minus 7 degrees, Freezing Level rising to 600M
Thursday - (2 to 6cm of snow), Strong Winds from the West will lessen throughout the day but expect some snow transport in Alpine and upper Treeline elevation bands, possible unstable snow (wind slab) on multiple aspects at Treeline and Alpine elevation, Temp minus 7 degrees, Freezing Level 700M.
Friday - Forecast models indicate strong precipitation (30 cm to 50cm Snow and possibly 20mm of rain below treeline), Air temperature fluctuates briefly mid day ( from minus 1 to + 1 and back to below zero for the remainder of the day. Freezing level fluctuates 600M of elevation to 1600M and back down to 600M.
Posted on Wednesday January 8, 2020 by Ryan Shelly