Regions
Banff Yoho Kootenay.
The current storm has mostly petered out in the Rockies, with minimal new snow in the last 24 hours. However, heavy rain in Yoho Park has produced several large avalanches over the Field ice climbs. Ice climbers should should consider heading east.
Weather Forecast
A strong SW flow aloft is streaming moisture onto the west coast, but the punch is mostly gone from these storms by the time they reach the Continental Divide. Regardless, expect heavy rain in Yoho Park on Thursday, with light rain or flurries further east, possibility of up to 10 cm at Bow Summit. Cooling is expected to arrive on Saturday.
Snowpack Summary
Although these warm daytime temperatures are promoting overall snowpack settlement, the lower half of the snowpack remains poorly structured, with a weak based comprised entirely of facets and depth hoar. This problem is most pronounced in rocky, windswept terrain at treeline and higher where human triggering of full depth avalanches is possible.
Avalanche Summary
Good observations today in Kootenay Park and highway 93 N revealed a distinct lack of avalanche activity. Sunshine ski area reports a similar lack of avalanches. However, the low elevation rainfall resulted in widespread avalanche activity in the ice climbing gullies down in Field (on Mt. Dennis).
Confidence
Timing of incoming weather systems 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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.