Archived

Avalanche Forecast

Dec 10th, 2015–Dec 11th, 2015

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

3: Considerable

The avalanche danger rating below treeline will be considerable

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Don't be surprised by a touchy surface hoar layer that becomes more reactive at lower elevations. While natural avalanches are becoming less likely, storm slabs will still be easily triggered by riders in the right (or wrong) spot.

Weather Forecast

Today expect flurries and temps ranging from -3 to -10. Moderate S'ly winds will continue to load lee slopes. Flurries will taper off on Friday, with the possibility of some sun, which may destabilize the new snow. Late Saturday the next storm will arrive bringing more snow, with freezing levels at valley bottom.

Snowpack Summary

At treeline, 1m of new snow over the past week is settling and overlies a variety of surfaces. At treeline and below it sits on a surface hoar layer. The surface hoar layer is biggest and very reactive below ~1600m. On solar aspects it sits on a sun crust and may bond poorly. Surface hoar layers down ~1.5m are still reactive but harder to trigger.

Avalanche Summary

Yesterday there were reports of the Dec 2 surface hoar being remotely and skier triggered producing up to size 2 avalanches at ~1500m. At treeline and above, pockets of soft windslab have been easily triggered with propagations up to 80m wide. On Tuesday avalanches to size 3.5 were triggered naturally and by avalanche control.

Confidence

Timing of incoming weather systems is uncertain

Avalanche Problems

Storm Slabs

A 50-100cm thick slab overlies touchy surface hoar below treeline, and sun crust in the alpine. The surface hoar layer become more reactive at lower elevations. Expect the storm slab to be easy to trigger and capable of resulting in large avalanches.

Be wary of slopes that did not previously avalanche.Ski short pitches and regroup in safe spots.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3

Wind Slabs

With ~1m of new snow available for transport, strong S winds have formed wind slabs on N aspects in the alpine and tree-line. These pockets of windslab have been reported to be reactive to triggering.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Loose Dry

Above ~1800m temps remained cool and in areas sheltered from the wind there will be lots of loose snow available to sluff. Be aware that it can easily accumulate and trigger underlying slabs, especially the Dec 2 surface hoar / crust layer.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be aware of party members below you that may be exposed to your sluffs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2