Regions
Banff Yoho Kootenay.
Wind and storm slabs were less touchy than anticipated on Monday. However, another storm is approaching on Thursday with warm temps. The danger will climb to HIGH by Friday.
Weather Forecast
We expect to see another storm with an increase in temperature to track through the forecast region late on Thursday. Some models suggest up to another 30cm. Strong West wind is also expected. This combination of factors will increase the danger rating.
Snowpack Summary
The recent storm has deposited between 10 and 30cm of snow. Wind effect has generally been light, but soft wind slab formation has been observed in alpine areas where N and E winds have created a reverse loading pattern. All of this sits on a very weak snowpack structure.
Avalanche Summary
Explosive control today produced small results up to size 2 across the forecast region. A recreational party also reported remotely triggering a small size 1 avalanche from about 10m away. This slide occurred at treeline at the Hector Glades above highway 93N.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Friday
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.