Archived

Avalanche Forecast

Dec 31st, 2016–Jan 1st, 2017

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

In areas to the west of Trail and Castlegar a spotty layer of surface hoar has recently been reactive and extra caution may be required.

Confidence

Moderate -

Weather Forecast

SUNDAY: Flurries through the day following some light snow overnight. Winds easterly around 40 km/h at ridgetop. Treeline temperatures around -10C.MONDAY: Dry with some cloud and some sun. Winds northeasterly 20-30 km/h. Temperatures around -14C.TUESDAY: Dry and sunny. Winds northeasterly 10-15 km/h. Temperatures around -18C.

Avalanche Summary

The most interesting recent avalanche activity in the past week has been from the mountains west of Trail and Castlegar, where there have been four reports of small avalanches running on the mid-December surface hoar layer. On Thursday, a size 1.5 avalanche ran naturally on this layer on a south aspect at 2000 m. on a On Wednesday, a ski cut produced a size 1 persistent slab on a south aspect at 2100 m which was 40 cm thick. On Tuesday, a skier triggered a size 1.5 slab on a northeast aspect at 2100 m with a thickness of 40-60 cm. On Monday, a skier triggered a slab on this layer on a northeast aspect. Extra caution is still recommended in this area in places where surface hoar may still be preserved. In other news, a skier triggered a size 1.5 storm slab avalanche near Nelson on Thursday on a northeast aspect at 1850 m which was 15-25 cm thick

Snowpack Summary

30-60 cm of snow has accumulated since Monday. The new snow sits over a variable interface which may consist of wind scoured surfaces or old wind slabs in exposed terrain, surface hoar up to 5 mm in sheltered areas and/or a freezing rain crust. Recent test results suggest the layer is gaining strength but may still be reactive in isolated areas. Recent strong winds have been from a variety of directions and have been loading leeward and cross loaded features in wind exposed terrain. The mid-December interface is now down 40-100 cm. This layer appears to be well bonded in many parts of the region but has recently been reactive in the mountains west of Trail and Castlegar where the interface is down around 40 cm. It appears that preserved surface hoar is creating an isolated problems for this area and three skier trigger avalanches have released on this layer between Monday and Wednesday. On Thursday, the interface was also reported to be reactive to snowpack tests in the Valhallas and the mountains north of Nelson. It will be important to continue to track how this layer evolves during the upcoming period of high pressure.

Avalanche Problems

Wind Slabs

Wind slabs may remain in the immediate lee of ridgelines. Small pockets of fresh wind slab may develop on south facing slopes when winds shift round to the north. These could become locally unstable on steep south-facing slopes when the sun comes out

Use caution in lee areas. Recent wind loading has created wind slabs.Use ridges or ribs to avoid pockets of wind loaded snow.Watch for signs of reverse loading; winds have changed direction.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2