Archived

Avalanche Forecast

Feb 16th, 2018–Feb 17th, 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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

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

Regions: Sea To Sky.

Southern parts of the region near Squamish may get enough snow for HIGH danger. Prepare to scale back your terrain choices if you see heavy snowfall or blowing snow in your local area.

Confidence

Moderate - Track of incoming weather systems is uncertain

Weather Forecast

SATURDAY: Moderate snowfall with 15-30 cm throughout the day, strong southwest wind, freezing level up to 800 m with alpine high temperatures around -7 C.SUNDAY: Clearing and cooling with moderate northeast wind and alpine high temperatures around -15 C.MONDAY: Mostly sunny, light northeast wind, alpine high temperatures around -15 C.

Avalanche Summary

On Friday, several small storm slabs (size 1) were reactive below ridgetops and other wind-loaded slopes at treeline and alpine elevations.Several large cornices collapses were reported last week. One resulted in a fatal accident in the Callaghan area on Saturday. A snowmobiler was parked 7-10 m back from the edge of a corniced ridge when a large chuck broke off and took the rider down the slope. See here for a full report. A similar incident occurred nearby the same day, but the person only suffered minor injuries. Fragile cornices continue to be a concern in the region.

Snowpack Summary

15-30 cm of new snow is expected to form fresh storm slabs on Saturday. The new snow is burying hard wind-affected snow in exposed terrain, a hard crust below 1900 m, and a sun crust on south-facing alpine slopes. The mid-January crust is now buried beneath 150-200 cm of settled snow, but a heavy trigger such as a cornice fall could potentially wake up this layer. The lower snowpack is generally strong and well-settled.

Avalanche Problems

Storm Slabs

New snow and wind will form fresh slabs on Saturday, particularly in southern parts of the region where up to 30 cm of new snow is expected. Storm slabs will be extra reactive in wind-affected terrain at higher elevations.

Minimize exposure during periods of heavy loading from new snow and wind.Be cautious as you transition into wind affected terrain.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Cornices

Large, looming cornices have formed along ridgelines. They need to be given an extra wide berth from above and below. A large cornice collapse in the wrong location may have the ability to trigger a large avalanche on the slope below.

Falling cornices may trigger large avalanches on the slopes below.Stiff cornices can easily pull back into flat terrain at ridgetop if they fail.

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 2.5