Avalanche Forecast

Issued: Feb 1st, 2018 5:13PM

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

Avalanche Canada jlammers, Avalanche Canada

New snow and extreme winds will keep the avalanche danger elevated at higher elevations on Friday. The avalanche danger is expected to rise throughout the day.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

Friday: 10-20cm of new snow / Strong to extreme westerly winds / Freezing level at 1400mSaturday: Light flurries / Light and variable winds / Freezing level at 1200mSunday: 5-10cm of new snow / Light southwest winds / Freezing level at 2300mNote: Confidence is low for forecast wind values and precipitation amounts for Saturday and Sunday.

Avalanche Summary

Explosives control on Tuesday and Wednesday triggered lingering storm slabs at treeline and above - mostly in the size 1.5-2 range. The exceptions were a size 3 and a size 3.5 slab that were explosives-triggered on rocky, cross-loaded alpine slopes. The exact failure plane of these avalanches is unknown.Looking forward, continued snow and wind on Friday morning is expected to promote a new round of wind slab activity in higher elevation lee terrain.

Snowpack Summary

As of Thursday morning 10-15 cm of new snow had fallen and was redistributed by strong southerly winds into fresh wind slabs in exposed lee terrain. At lower treeline and below, generally light amounts of snow now overlie a melt-freeze crust which formed during last Monday's warm storm. 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
New snow and wind on Thursday night are expected to form new wind slabs in higher elevation lee terrain. This new snow overlies older storm slabs which are gaining strength but may remain sensitive to large triggers in steep, unsupported terrain.
Be alert to conditions that change with elevation.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, South West.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices
Recent heavy snowfall and high winds have formed fragile new 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, South.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 2nd, 2018 2:00PM