Tuesday February 4, 2020
Cornice Fall, Wet Slab, Loose Wet, Wind Slab, Storm Slab
Travel & Terrain Advice
Natural Avalanches possible. Human triggered avalanches likely in the Alpine. There is a good amount of precipitation expected over the next 48 hours on Vancouver Island. Be aware as you move through the terrain for shooting cracks and signs of instability (including new avalanches) especially at Treeline and Alpine elevation bands. Convex unsupported terrain features in leeward (down wind) terrain would be an area to be highly cautious of when navigating through the backcountry this week. 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 or Rain AND/OR signs of snow transport by strong winds exists in your area.
No new avalanches reported in the past 48hrs.
Tuesday and Wednesdays’s rainfall will hasten potential for cornice fall. New snowfall and strong winds will create new cornice growth at mountain top and on cross loaded terrain. In addition to fresh cornice growth, new rainfall, expected to arrive late Tuesday and throughout Wednesday will overload the cornices and increase the probability for a natural cornice failure cycle and/or be primed for human triggering. Avoid all travel nearby (above/below) to cornices.
Tuesday and Wednesday’s forecast of snow and rain will also exacerbate stability and further stress the snowpack. New snow and rain fall Tuesday/Wednesday could create dense moisture laden upper snowpack primed for triggering within the upper 50cm of the snowpack where new storm and wind driven layers exist and are not yet consolidated.
A rising freezing level above the Alpine on Tuesday coupled with major loading from rainfall in excess of 30mm will excacerbate bonding of new storm snow and wind driven snow interfaces within the upper 50cm of the snowpack. Loose Wet avalanches can release on steep unsupported terrain adjacent rocks and/or trees. Expect snow entrainment to occur when/if a loose wet avalanche is initiated.
Moderate precipitation in the form of storm snow coupled with sustained strong winds on Tuesday into Wednesday could promote wind slab instabilities (particularly in leeward or down wind areas on Vancouver Island. Expect all Alpine environments in leeward/down wind terrain to be likely areas to trigger a wind slab avalanche on Tuesday and Wednesday.
Moderate precipitation in the form of storm snow on Vancouver Island early this week will cause instabilities in the snowpack. Expect Alpine (human triggered avalanches likely) and Treeline (human triggered avalanches possible) On Wednesday treat the avalanche hazard as “human triggered avalanches likely” at Alpine and Treeline elevation bands where a mixture of rain and new snow will increase avalanche risk on storm slab layer.
A variety of melt freeze crusts exist within the upper snowpack. The more recent snowfall from Sunday’s cooler temperatures have deposited fresh snow on the most recent melt freeze crust. Snowpack tests are providing results on this layer, as more winds travel through the area today and tommorow we should expect substantial new wind loading and likely wind slab avalanche hazard in leeward (downwind) terrain.
The massive rain events from the past week added major moisture content to the Vancouver Island snowpack. Fortunately, with the more recent cooler (below zero) air temperatures we have experienced, the snowpack has consolidated. The most important hazard at this time exists within the upper 10 to 40 cm of the snowpack and exists as a result of new storm snow and wind activity that has occurred in the past 48 Hours.
|Surface||10 -40 cm of light dry storm snow and/or firm wind loaded snow in leeward terrain|
|Upper||Melt freeze crust that is providing results on testing as new snow gradually bonds to this crust layer|
|Mid||Well Bridged due to abundance of moisture in snowpack and below freezing air temperatures|
Cool air temperatures and moderate storm snow events have deposited 1 foot (30 cm) or more of snow onto the snowpack over the course of this past weekend.
Tuesday 7 - 12mm Rain and 7 - 21 cm Snow , Winds Strong to Moderate from the South, Freezing level shifting from 300M to 2500M later in the day.
Wednesday 6- 40 mm Rain, Winds Strong transitioning to Light later in day from the West, Freezing level shifting from 2500M to 1400 meters.
Thursday 3-12 cm, Winds Light transitioning from the North to the South, Freezing level 1500 meters.
Posted on Monday February 3, 2020 by Ryan Shelly