Avalanche Forecast

Issued: Mar 4th, 2016 8:16AM

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

triley, Avalanche Canada

South Columbia.

Forecast new snow and wind will continue to develop storm slabs over surface hoar and crusts. Expect remote triggering and wide fracture propagations resulting in large avalanches. Conservative terrain selection is essential.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

3-5 cm forecast overnight with freezing levels remaining above 1500 metres and strong southwest winds. Another 10-15 cm during the day on Saturday with strong southerly winds and freezing levels creeping up to 2000 metres. There is a chance of sunny periods in the late afternoon when a brief break between storm pulses moves across the region. Warm, wet, and windy on Sunday. A weak ridge should drop freezing levels to valley bottoms by Monday morning, before broken or scattered cloud allows the sun to bring the freezing level back up to 1500 metres during the day.

Avalanche Summary

On Thursday, natural avalanches up to size 2.0 were reported as well as several remotely triggered slab avalanches up to size 2.0. These slides occurred on all aspects, at all elevations, and were generally 40-60 cm deep. Reports from Tuesday and Wednesday include more of the same plus evidence of a widespread natural avalanche cycle that occurred early Monday, primarily in the Monashee Mountains, with avalanches up to Size 3 running on surface hoar buried late February.

Snowpack Summary

40-60 cm thick storm slabs are bonding poorly to on a crust on previously sun-exposed slopes and surface hoar (February 27th) on shady and sheltered slopes. Thicker and touchier wind slabs are lurking throughout exposed terrain at and above treeline. A weak layer of surface hoar and/or a sun crust buried February 21 is now close to a metre below the surface. Where it exists, this layer may become reactive to human triggers as the overlying slab develops. The surface hoar and/or crust layer buried February 10 is likely down over a metre. This layer was less reactive over the past week with cooler temperatures, but remains a concern for large triggers like cornice falls or a smaller avalanches stepping down. Cornices are large and potentially weak and should be avoided where possible.

Problems

Storm Slabs

Storm slabs are expected to continue to develop with forecast new snow and wind. Storm slabs may be sitting on a crust or crust/surface hoar combination down 40-60 cm that is easy to trigger and may result in wide fracture propagations.

Be cautious as you transition into wind affected terrain.>Minimize exposure during periods of heavy loading from new snow, wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The February 10th buried surface hoar layer may be down about one metre in most areas. Heavy loading from new snow and wind, as well as high freezing levels may increase the likelihood of triggering this deeply buried weak layer.

Minimize exposure to sun exposed slopes when the solar radiation is strong.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Cornices

Cornices are large and fragile. Continued loading from new snow and wind may result in natural cornice falls.

Extra caution needed around cornices with current conditions.>Cornices become weak with daytime heating. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 5th, 2016 2:00PM