Archived

Avalanche Forecast

Dec 11th, 2015–Dec 12th, 2015

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Kootenay Boundary.

Touchy fresh wind slabs at higher elevations combined with lurking persistent weaknesses at lower elevations means you can't let your guard down this weekend.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Saturday: Increasing cloud and snowfall throughout the day with 10-15cm possible by Sunday morning. Freezing levels in valley bottoms and light southwesterly becoming moderate to strong southerly ridgetop winds. Sunday: Another 5-10cm possible with freezing levels peaking at 1400m and moderate southerly easing to light southwesterly ridgetop winds. Monday: Mainly cloudy with light snowfall and cooler temperatures.

Avalanche Summary

Reports from Thursday include an explosives-triggered 50cm thick persistent slab avalanche running on the early-December surface hoar on a convex roll below treeline in the Monashees.

Snowpack Summary

Recent heavy rain to treeline elevations and wet snow above saturated and loaded the upper snowpack, forming a thick crust which now has up to 20-25cm of fresh snow on top (with perhaps a thin crust within it). Weaknesses linger within the recent snow as well as at deeper old snow surface interfaces, which consists of facets, surface hoar, and/or a crust at upper elevations (especially on southerly aspects). The most critical of these is surface hoar buried early December (now likely down 50-100cm), which has the potential for remote triggering, extensive releases and prolonged sensitivity to triggers. It is likely lurking in most sheltered areas treeline and below. The thick mid-November crust is just under this weakness.

Avalanche Problems

Persistent Slabs

The weakness buried early-December is becoming more stubborn to trigger, but lingering pockets of buried surface hoar may maintain touchy conditions on sheltered slopes in the northern part of the region, especially in the 1400-1800m elevation range.

Be alert to conditions that change with elevation.>Make observations and assess conditions continually as you travel.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 5

Storm Slabs

New snow will likely be sensitive to human triggers, and particularly deep and weak on the leeward side of ridge crests and terrain breaks, and in wind-loaded chutes.

Be cautious as you transition into wind affected terrain.>On steep slopes, pull over periodically or cut into a new line to manage sluffing.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 3