Monday January 6, 2020
Cornice Fall, Wet Slab, Loose Wet, Deep Persistent Slab, Storm Slab
Travel & Terrain Advice
Monday is likely the best day to get out explore terrain however later in the day Rain and/or snow is forecast to fall in many parts of the island. As incoming strong rates of precipitation arrive, so too will additional load and stress to the snowpack. Dial back your objectives in terms of slope angle and keep an eye out for snow cracking underfoot, whumpfing and other signs of instability.
Observed Size 1 loose dry “sluff” avalanches in extreme terrain. Cracking and small size 1 avalanches triggered by ski cuts in steep unsupported terrain on the storm snow we received during the weekend in leeward terrain.
Monday and Tuesdays’s rainfall will hasten potential for cornice fall. Extreme winds and up to 90cm of additional snow on Tuesday in Alpine will increase the probability for cornice failure due to High winds and new snow.
Monday and Tuesday’s forecast of snow and rain will also exacerbate stability and further stress the snowpack. New snow and rain fall Monday/Tuesday could create dense moisture laden upper snowpack primed for triggering.
On Monday and Tuesday, rain is forecasted at treeline and Below Treeline elevation bands, further aggravating the recent storm snow interface from earlier in the weekend.
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 in the next 24 HRS. 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.
Major precipitation in the form of snow and wind will cause major instabilities in the snowpack over the next 24-36HRs. Expect all Alpine and Treeline environments to be very likely areas to trigger an avalanche.
Despite the major warm up earlier in the weekend, the air temperatures have dropped back below zero and have helped to consolidate the snowpack. New storm snow has begun to settle. In shallow snowpack regions, a more pronounced surface hoar layer is providing results that indicate less consolidation in the upper snowpack. Monday evening and Tuesday forecasted rainfall may increase load on this problematic layer and contribute to a possible natural avalanche cycle at Alpine and upper elevation Treeline Environments.
|Surface||Depending on Aspect and elevation, anywhere from 20cm-40cm of light dry powder snow on a firm rain crust|
|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||A well consolidated mid pack that includes a facet and Surface Hoar Layer approximately 60cm down are increasingly more stubborn to triggers during snow pack testing|
A Major warm up on Friday and extensive rains were felt up to the Alpine Mountain environment. Late Friday, the air temperature dropped and into Monday we have received a consistent and moderate snowfall amount in excess of 30cm to 45cm depending on aspect, elevation and location on Vancouver Island. The skiing has been great!
A large storm cycle of strong precipitation, wind and freezing level fluctuations is expected over the next 24 HRS.
Monday - Air temps will rise above zero, (2cm-10cm of snow) in the afternoon precipitation will shift to rain (5mm-20mm Rain) , Moderate mountain top Winds from the SW, Temps O degrees to +2 degrees, Freezing Level rising to 1850M
Tuesday - Big rise in air temperature will bring about extreme rain up to Alpine (20mm - 80mm Rain), Extreme Winds from the SW will lessen throughout the day but expect more snow transport, unstable snow on multiple aspects at Treeline and Alpine elevation, Temps +3 to -7 degrees, Freezing Level dropping from 2000M to 1,600M later in the day.
Wednesday - Forecast models indicate a major drop in air temperatures and light snowfall (1 cm to 5cm Snow), Air temperature steady at -7 with a freezing level at 600M of elevation.
Posted on Monday January 6, 2020 by Ryan Shelly