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Avalanche Forecast

Archived

Nov 22nd, 2012–Nov 23rd, 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

South Columbia.

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

Thursday Overnight: Increasing cloud with 0-3 mm precipitation. Freezing level at about 900 metres. Warmer in the South, but generally -4.0 in the alpine. Winds light from the SW.Friday: Cloudy with 4-7 mm precipitation, maybe a bit more in the North and the western upslope areas. Freezing level rising to about 1300 metres during the precipitation and then descending to near valley bottoms, -4.0 in the alpine. Winds increasing to SW 40 km/hr.Saturday: Cooling trend behind the storm as High pressure moves into the region, freezing level at valley bottoms. Expect -9.0 in the alpine. Winds should clock to the NW and decrease to about 20 km/hr.Sunday: Should still be under the influence of the High pressure. Cooler temps and light winds.

Avalanche Summary

No new reports of avalanches. If you any observations please share here.

Snowpack Summary

I suspect that there might have been some surface hoar growth Thursday morning due to overnight clear skies. If you have any observations, please share by email. The recent storm snow has been wind affected in the alpine and open areas at treeline. Some people are reporting a thin crust on solar exposed aspects that developed late last week (November 17th), and is now buried by the new storm. The freezing level went up to about 1500 metres during the recent storm. Snow levels taper off to below threshold by about 1200 metres. There is about 60-80 cms of recent storm snow above an early November crust, or series of laminated crusts. Tests have been showing easy to moderate SP (sudden planar) pops on weak facetted crystals at this crust interface, or within the crust sandwich.

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.