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Archived

Avalanche Forecast

Feb 1st, 2018–Feb 2nd, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

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.

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.

Avalanche Problems

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

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