Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
A major change in weather patterns on Tuesday night as a cold front from NE Alberta moves over the region bringing upslope snow starting Wednesday. If the forecast plays out, 25 cm of cold snow, generally light winds and -12 by Friday will give a full reset to the snow conditions. Switch your avalanche mindset back to winter.
Confidence
Moderate
Avalanche Summary
No significant new avalanches were reported or observed today, and both ski areas reported a reduction in avalanche activity associated with a strong overnight freeze and then cooler daytime temperatures.
Snowpack Summary
The heat wave has produced surface crusts on all aspects except due north above 2100 m, and this layer of crust/wet snow is about to get buried (Mar 20 layer). Initially, pay close attention to the bond between the incoming new snow, and the March 20 layer. We expect avalanches on this crust and their size will depend on how much snow falls. Expect a poor bond initially. Deeper in the snowpack, we expect the cooling trend will strengthen the deeper weak layers (Feb 3).
Weather Summary
Weather changes start tonight as a cold front moves over the area from the NE (upslope) direction. Temperatures will cool progressively through Friday and up to 25 cm of snow is expected by the end of the day on Thursday.
It starts with 5-10 cm on Wednesday, then Thursday is the big day for snow, with up to 20 cm expected throughout the day. Winds will generally be light to moderate and temps will reach -12 by Friday.
Terrain and Travel Advice
- Closely monitor how the new snow is bonding to the crust.
Avalanche Problems
Persistent Slabs
The Feb 3 crust/facet interface is down 40-90 cm and has been producing large avalanches all week. We expect this layer to strengthen as colder temperatures penetrate the snowpack, but this may take a few days to play out. A big warm-up followed by a big cool-down is generally good for snow stability.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1.5 - 3
Deep Persistent Slabs
During the warm snap, many avalanches released on the ground resulting in large avalanches, most commonly in thin, steep, rocky terrain in the alpine. The incoming cooler temperatures will reduce the likelihood of triggering this problem, but the weak snow at the base of the snowpack remains.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2 - 3.5