Avalanche Forecast

Issued: Mar 6th, 2016 9:08AM

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

triley, Avalanche Canada

South Columbia.

Storm slabs continue to be a concern. Wide fracture propagations are possible where the storm snow is sitting on a weak buried layer of surface hoar.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A clearing and cooling trend should bring freezing levels down to valley bottoms overnight. A mix of sun and cloud on Monday with periods of light precipitation and light westerly winds. A mix of sun and cloud on Tuesday with light winds. A diurnal freeze/thaw cycle setting up with freezing down to valley bottoms overnight and then rising up to 1500 metres during the day. No change for Wednesday, but a new system moving into the region on Wednesday night.

Avalanche Summary

Natural avalanches up to size 2.5 were reported on Saturday. Skier accidental, skier remote triggered, and natural avalanches up to size 2.5 continued to be reported on Friday. Most of these avalanches were releasing in the storm snow, or at the storm snow/surface hoar interface. 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.

Snowpack Summary

Some reports from the Monashees of a thin melt-freeze crust that has developed within the storm snow that has been reactive up to size 2.0 on Sunday. Variable amounts of new snow and wind have continued to develop storm slabs 40-60 cm thick that are bonding poorly to 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

New snow may not be bonding well to a thin crust that developed between storm pulses over the weekend. The 40-60 cm storm slab may not be well bonded to an earlier crust or crust/surface hoar layer buried on February 27th.

Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Cooling temperatures and dropping freezing levels may decrease the likelihood of triggering this deeply buried surface hoar layer. This is becoming a low likelihood but high consequence scenario.

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

3 - 5

Cornices

New cornice growth is large and may fall off naturally due to daytime warming.

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 7th, 2016 2:00PM