Avalanche Forecast

Archived

Nov 24th, 2012–Nov 25th, 2012

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Cariboos.

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

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Sunday: A few clouds with the possibility of light flurries / Light to moderate northwest winds / Freezing level at 800mMonday: Mainly sunny / Light to moderate northwest winds / Freezing level at 900mTuesday: Mainly sunny / Light to moderate northwest winds / Freezing level at 1200m

Avalanche Summary

Just before the weekend we received a report from the Valemount area of a snowmobile triggering a size 2.0 avalanche that was about 70 cm deep and about 80 metres wide. The avalanche was triggered from a shallow weak area, and suspect that the weak layer was either the November crust or buried surface hoar. Please send us an email if you have any observations.

Snowpack Summary

Snow accumulations from Friday were highly variable in the region with some areas receiving over 30cms over the 24hr period. Although alpine wind data has been sparse, velocities in neighboring regions have been in the upper end of moderate. That said, I'd be highly curious about the possibility of windslabs in exposed areas. The recent snowfall adds to the healthy amounts that have fallen over the past few days. There may be a thin buried surface hoar layer down about 85 cm in the alpine. As well, the November rain crust now exists over 100cm down in some locations and may exist in combination with facets. Buried persistent weak layers may become reactive with the recent storm loading.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.