Avalanche Forecast

Issued: Feb 5th, 2018 4:24PM

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 mgrist, Avalanche Canada

Wind slabs and cornices are the main concerns right now: Give both a wide berth and limit your exposure to overhead hazard.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Tuesday: Isolated flurries (5cm possible) / Light to moderate westerly winds / Freezing level 1000m. Wednesday: 5-10cm of snow / Moderate gusting strong west winds / Freezing level at 1600mThursday: Mainly cloudy with isolated flurries (up to 5 cm possible) / Light to moderate north westerly winds / Freezing level at 1200m

Avalanche Summary

On Monday, cornice control work with explosives resulted in a size 2.5 avalanche which ran on the early January crust/facet layer. On Sunday, ski cutting produced several size 1 to 1.5 soft slabs on immediate down wind (lee) features. Expect wind slabs to remain reactive to human triggers as winds continue to be moderate to strong with small amounts of new snow available for transport. See here for a good MIN post summarizing conditions near Whistler. On Saturday we received reports of a skier triggered size 1.5 avalanche near Whistler on a north west aspect around 2100m.

Snowpack Summary

We've had small amounts of new snow over the past several days. Temperatures had been above zero at tree line for much of the weekend, but dropped to more seasonal values on Monday. Winds, however, have been consistently strong from the south (east), creating reactive wind slabs in exposed downwind (lee) terrain. At lower treeline and below, generally light amounts of snow or rain now overlie a melt-freeze crust which formed during Monday's warm storm from a week ago.The new snow adds to the 170cm 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 down wind (lee) features at higher elevations.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices
Heavy snowfall and high winds a week ago formed fragile cornices. These monsters may surprise with nasty consequences. Use extra caution around ridge crests.
Falling cornices may trigger large avalanches on the slopes below.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 6th, 2018 2:00PM