Avalanche Forecast

Issued: Nov 23rd, 2012 8:38AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Storm Slabs and Persistent Slabs.

istorm, Avalanche Canada

Sea To Sky.

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the forecaster's blog for further details on interpreting early season bulletins.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

The storm that arrived overnight Thursday moved out of the region Friday. Incoming air is looking cooler and drier. Precipitation: no significant snow or rain forecast through Monday. Wind: light SE Saturday veering to light NW Sunday and backing to the West on Monday. Temperature: cooling with below freezing temperatures at all elevations overnight and around 800m or 900 m during the day. Alpine temperatures around -5 to -10C. You're likely to see at least some sun this weekend, more likely on Sunday.

Avalanche Summary

In the limited reports we have, Friday's storm snow is quite reactive with natural avalanches to size 1.5 reported near treeline in the Whistler area. I suspect the arrival of forecast cooler temperatures will end natural activity; however, I suspect human triggering may still be worth thinking about at higher elevations. Explosive testing in the Whistler area only released few and small avalanches on the the early Nov. crust.

Snowpack Summary

The total snowpack depth at treeline is around a metre. Alpine areas are deeper but more variable with fat drifts and boney rocks. Most slopes below treeline are still below threshold depths for avalanches. Weaknesses likely exist within the recent storm snow, but should heal quickly. The main snowpack feature worth noting is a rain crust buried in early November and now down around 80cm at treeline as as deep as 1.5m in alpine areas. A weak layer of facets on top of and within this crust is worth remaining suspicious about (sudden collapse fracture character with propagation potential with snowprofile/snowpack tests; however, explosive testing near Whistler didn't generate many results). Widespread whumpfing and cracking on this layer has also been reported from the Whistler area. Because this weakness is so close to the ground in most areas, associated avalanche activity will likely be limited to slopes with smooth ground cover (e.g. scree slopes, rock slabs, summer firn, glaciers, etc.). For more information check out the telemarktips.com forum , the Mountain Conditions Report, and Wayne Flann's Avalanche Blog.

Problems

Storm Slabs

Fresh wind slabs below ridgecrests, behind terrain features, and in cross-loaded gullies may remain sensitive to human triggers. Particularly where they are sitting on a previously exposed or lightly buried crust from early November.

Assess start zones carefully and use safe travel techniques.>Avoid cross loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Large avalanches running on a crust near the base of the snowpack are possible, particularly on slopes with smooth ground cover. Remote triggering and step-down avalanches might be a concern with this weakness.

Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Nov 24th, 2012 2:00PM