Avalanche Forecast

Issued: Mar 4th, 2016 8:05AM

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

Cariboos.

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

5-10 cm forecast overnight with freezing levels remaining above 1500 metres and strong southwest winds. Another 5-10 cm during the day on Saturday with strong southerly winds and freezing levels creeping up to 1800 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

Reports from Thursday that several natural size 2.0 slab avalanches and one size 3.0 storm slab were suspected to have released on the late February surface hoar layer. There was also a report of a size 3.0 avalanche remotely triggered by a skier that was 20 metres away. On Wednesday, there were reports of a few natural slab avalanches up to size 2.5 failing on the late Feb. sun crust/surface hoar combo. These slides were from S-E aspects at treeline and showed impressive propagation. Reports from Tuesday include more evidence of the widespread natural avalanche cycle early Monday, with avalanches up to Size 2.5.

Snowpack Summary

30-60cm thick storm slabs are bonding poorly to a crust on previously sun-exposed slopes and surface hoar (February 27th or late February) on shady and sheltered slopes. Thicker and touchier wind slabs are lurking throughout exposed terrain at and above treeline. A couple of sun crusts might exist in the upper 50-70cm on southerly aspects. The surface hoar and/or crust layer which was buried February 10 is now down around a metre and is still producing isolated hard sudden results in snowpack tests. Large cornices will be getting weak with warmer temperatures.

Problems

Storm Slabs

Forecast new snow and wind are expected to continue to develop storm slabs at all elevations. Storm slab avalanches in motion may trigger persistent weak layers.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

There are two buried surface hoar layers of concern. The February 27th layer is down 40-60 cm and the February 10th layer is generally 15-30 cm deeper in the snowpack. Buried surface hoar may be associated with a crust that allows for wide fractures.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 5

Cornices

Cornices are large and fragile. Warm temperatures, high freezing levels, and continued loading from wind and snow 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.

Likelihood

Possible

Expected Size

2 - 5

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