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Avalanche Forecast

Archived

Nov 23rd, 2012–Nov 24th, 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

Overnight and Saturday: Cooling trend behind the storm as High pressure moves into the region, freezing level at valley bottoms. Expect -10.0 in the alpine. Winds should clock to the NW. No precipitation expected.Sunday: Should still be under the influence of the High pressure. Cooler temps and light winds.Monday: Continued High pressure.

Avalanche Summary

We have 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. See photo here. 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

Reports show that the region has had between 20-40 cm from the recent storm. Near Valemount the HS was 145 cm at 1975 metres during the storm. The foot penetration was 60 cm, so there is quite a bit of snow available now for transport by the strong winds during the day Friday and forecast for Friday night. The November rain crust was found down 100 cm and has been described as a weight bearing crust. There may also be a thin buried surface hoar layer down about 70 cm in the alpine. 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.