Avalanche danger will increase throughout the day due to warm sunny weather.
Plan on finishing early and minimizing your exposure to overhead avalanche terrain. Read more in this Forecasters' Blog.
Cornices are large and will weaken with daytime warming. Stay well back from them on ridges and avoid travelling beneath them. A cornice fall has the potential of triggering slabs on the slopes below.
The snow surface will weaken over the course of the day as warm air and sunny skies prevail. The most likely areas to get into trouble are above terrain traps.
A prolonged period of warm air and sunny skies is heating the snowpack, increasing the likelihood of reactivating buried weak layers. It is uncertain if and when large slab avalanches may release, but the possibility remains during this warm period. Deeper releases are most likely in shallow snowpack areas along the eastern slopes of the Rockies.
WEDNESDAY NIGHT: Clear skies, light east wind, alpine temperatures stay slightly above freezing with sub-zero temperatures in the valleys.
THURSDAY: Clear skies, light southeast wind, freezing level reaching 3000 m and treeline temperatures reach +7 C.
FRIDAY: Clear skies, light wind, alpine temperature 5 C, freezing level steady at 3000 m and treeline temperatures around+7 C.
SATURDAY: Clear skies with some high clouds in the afternoon, light west wind, freezing level around 2500 m and treeline temperatures around +5 C.
Natural avalanche activity has been reported on sun-exposed slopes over the last few days, including an impressive photo in this MIN report from Kakwa on Tuesday. Most activity has been relatively small (size 1-1.5) wet loose avalanches, but they will likely get bigger when it gets warmer on Thursday and Friday. A few wind slab avalanches (up to size 2.5) were reported over the weekend, but this problem has likely settled down since then. There have been some large deep persistent slab avalanches triggered by warming to the south around Jasper and Banff, but we are uncertain whether this problem will extend into the North Rockies.
Looking forward, warm sunny weather will drive avalanche danger with wet loose avalanches likely and the possibility for deep persistent slab avalanches in some areas. These problems are best managed by minimizing your exposure to avalanche terrain when it gets warm.
Warm temperatures are melting the surface on all but the highest north-facing slopes, creating weak surface snow during the heat of the day. Crusts may form overnight. Large cornices hang above many ridgelines and will also weaken with the warming.
As heat penetrates deeper into the snowpack it has the potential to reactivate deeper weak layers, including a layer from mid-February and basal layers. The most likely areas to be concerned about deeper weak layers are shallow parts of the region along the eastern slopes of the Rockies like Core Lodge, Wolverine, Bullmoose, Upper Burnt and perhaps around Mt. Robson.
