If you're headed to the Bonnington Range please read the Avalanche Observations section on the Forecast Details page. The snowpack in that area seems to hold a low probability-high consequence avalanche problem.
Summary
Confidence
Fair - Intensity of incoming weather is uncertain on Wednesday
Weather Forecast
Up to 25mm expected overnight Tuesday accompanied by 30-45km/hr winds from the SW gusting to 80km/hr. Wednesday: 5-10cms of new snow. Ridgetop winds 40-55km/hr from the West. Freezing levels near 600m. Thursday: New snow 5-10cms. Ridgetop winds 50-60km/hr from the NW. Freezing levels fall to valley bottom. Friday: Mainly dry conditions. ridgetop winds 60-80km/hr from the NW.
Avalanche Summary
No new avalanche observations reported today. Sunday saw several natural small size 1-2 avalanches on all aspects, and explosive avalanche control produced size 1-2.5 on SE-SW aspects. On Saturday in the Bonnington Range several avalanche incidents occurred. The first reported was remotely triggered by a skier, it produced a size 3 slab avalanche from ridgetop. This slide was at 2200m on a North-North East aspect and ran 400m in length. There was also a skier remote size 2 from the same group. There were no involvements with these avalanches. Another group of skiers had similar observations from this mountain range. They triggered a skier remote size 3 from 100m away, additionally a size 2 sympathetic occurred. The size 3 crown depth was 50-120cms, 200m wide, and ran 400m. Both avalanches initiated from 1800m on S-SE aspects. The suspect layer possibly being the Mid December surface hoar/facet layer. This is a good indicator to be aware of the sensitivity in your local snowpack, and make observations while you travel. With forecast snow, wind and rising freezing levels the avalanche danger will be on the rise.
Snowpack Summary
Over the weekend up to 35cms of new snow fell. This new snow came in denser that the previous, cold storm. This has formed storm slabs at all elevations, and wind slabs in the alpine and at treeline. These slabs are reported to be quite reactive due to their poor bond on the cold snow interface below. The second layer of concern is a crust that lies down 50-60cms and exists below 1900m. The bond with this crust appears to be quite good, however, on steep slopes this could easily act as a weak interface, potentially creating a layer for avalanches that initiate in the upper snow to step down to. This will be a layer to watch with more snow load and rising freezing levels on Tuesday-Wednesday. Layers of concern deeper in the snowpack include a surface hoar/facet layer from mid-December and weak basal facets at the base of the snowpack in shallow snow areas. These layers have become less of a concern in the vast majority of locations. Last Saturday the mid December layers is suspect to several large avalanches that occurred in the Bonnigton Range. This is a lingering layer of concern, that reflects low probability but high consequence. Snowpack depths in the region are around 240 cm.
swerner,
Avalanche Canada
