Avalanche Forecast

On Tuesday and Wednesday, operators across the region used explosives on a wide range of slopes (aspect and elevations). Explosives produced several smaller storm slab and wind slab avalanches, but more importantly numerous size 2.5- 3 deep persistent slabs that released at the base of the snowpack. This tells us large enough loads have strong potential to initiate one of these deep avalanches and that human triggering is a serious concern, particularly in thin or variable depth spots (rocks, thin to-thick areas) in the snowpack.

On Monday, A few small (size 1 to 1.5) human-triggered slabs were reported, mostly failing on a 30 cm deep surface hoar layer. A few larger (size 2) human-triggered slabs were reported in the Esplanade range. Explosive avalanche control produced multiple large (size 2) and one very large (size 3) deep persistent slab.

Last Saturday, a skier triggered a size 2.5 avalanche on a low-angle alpine slope near Golden. This avalanche had a 1 m crown and again ran on the facets near the bottom of the snowpack.

15-25 cm of recent storm snow can be found in sheltered areas, while open terrain has been wind affected. The recent snow overlies a mid-January interface that includes small surface hoar all the way into the alpine in some parts of the region as well as a rain crust that can be found up to 2000 m in most parts of the region.

There are two additional concerning weak layers in the top metre of the snowpack. The first is a layer of surface hoar from early January - down 30-50 cm. The second is a layer of surface hoar, facets, and a crust from December, down 40-90. The surface hoar is most prevalent in sheltered areas while crusts and any associated faceted snow have more uniform distribution.

The bottom of the snowpack contains yet more weak, faceted snow that continues to produce large avalanches and will likely persist for a prolonged period of time.

All of these interfaces are at their shallowest in the east of the region and all of them have produced avalanches recently.

In general, even in the west of the region, the snowpack is shallow and weak.

Thursday night

Clear. Light to moderate west winds.

Friday

Mainly sunny. Light southwest or northwest winds, more northerly with elevation. Treeline high temperatures around -5.

Mainly cloudy with scattered flurries bringing less than 5 cm of new snow in the afternoon. Finishing quickly in the evening. Light variable winds, mainly southerly. Treeline high temperatures around -8

Mainly sunny. Light to moderate northwest winds. Treeline high temperatures around -6.

More details can be found in the Mountain Weather Forecast.

• Be mindful that deep instabilities are still present and have produced recent large avalanches.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Wind slabs are most reactive during their formation.