Avalanche Forecast

Issued: Feb 6th, 2018 4:17PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

Avalanche Canada swerner, Avalanche Canada

Wind slabs and cornices are the main concern for Wednesday. Forecast new snow and strong winds will likely add a storm slab problem by Thursday morning. Be alert to changing conditions and increased hazard.

Summary

Confidence

Moderate - Timing of incoming weather systems is uncertain

Weather Forecast

Wednesday: 5-10 cm of new snow accompanied by strong southwest winds at ridgetop elevations. Freezing levels near 1500 m. Thursday: Another 10-15 cm expected overnight and tapering off throughout the day. Ridgetop winds light with strong gusts from the southwest. Freezing levels near 1400 m.Friday: A mix of sun and cloud as the arctic front shifts over the region. Alpine temperatures near -12 with a high of -4. Light-moderate ridgetop winds from the northeast and freezing levels near 900 m.

Avalanche Summary

On Monday, cornice control done with the use of explosives triggered numerous cornices up to size 2.5, mostly just entraining snow mass from the slope below. The larger cornice failure (2.5) did pull a small slab avalanche on the slope below. Cornices and wind slab avalanches remain touchy to rider triggers.

Snowpack Summary

We've had small amounts of new snow over the past several days. Winds, however, have been consistently strong from the south (east), forming reactive wind slabs in exposed downwind (lee) terrain. Snow surfaces vary with wind pressed, scoured or 10 cm of fresh, low density snow in the alpine. Treeline and below treeline a melt-freeze crust exists with moist snow below 1500 m. The new snow adds to the 170 cm of snow that fell during the last few weeks of January. These series of storms were accompanied by strong to extreme winds which resulted in extensive scouring and impressive cornice growth in upper elevation terrain. These accumulations sit on a crust from mid-January which generally shows signs of bonding to the overlying snow; however, it has the potential to "wake-up" with a large trigger such as a cornice fall.Below this, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent winds have created pockets of reactive soft slab below ridge crests and on immediate leeward features at higher elevations. New wind slabs may form with forecast snow amounts.
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Stay off recent wind loaded areas until the slope has had a chance to stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices
Fragile looming cornices exist. They require respect and may surprise you with nasty consequences. Use extra caution around, on and below ridge crests.
Give cornices a wide berth when travelling on or below ridges.Falling cornices may trigger large avalanches on the slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Valid until: Feb 7th, 2018 2:00PM