Archived

Avalanche Forecast

Feb 22nd, 2017–Feb 23rd, 2017

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

2: Moderate

The avalanche danger rating in the alpine will be moderate

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

2: Moderate

The avalanche danger rating in the alpine will be moderate

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: Lizard-Flathead.

Natural deep persistent slab avalanches size 3.0 have been reported in this region.

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

Tonight: Overcast with a chance of 3-5 cm of new snow combined with light northwest winds and freezing to valley bottoms. Thursday: Broken skies with light variable winds and -15 in the alpine. Friday: Mix of sun and cloud with light variable winds and -15 in the alpine. Saturday: Mostly sunny with moderate northwest winds and alpine temperatures close to -20.

Avalanche Summary

There was a report on Tuesday of a natural avalanche size 3.5 on Mt Hosmer on an East aspect at 2100 metres that appears to have released on or stepped down to the weak deep persistent layer of sugary facets near the ground. On Wednesday we had a report of a size 3.0 avalanche on "Big Steep Mother" bowl on a northeast aspect at 2100 metres in the alpine in the Lizard range. This avalanche appears to have been started by a cornice fall that released a storm slab that then "stepped down" to deeply buried weak facets. Explosives control on Wednesday resulted in cornice falls up to size 2.5, and storm slabs with some pockets of un-supported terrain stepping down to size 2.5. All avalanches reported were from north-northeast aspects.

Snowpack Summary

There is now 50-60 cm of storm snow that is expected to settle into a storm slab. This slab sits above a thick rain crust below 1900 m and a generally well settled snowpack. Isolated basal weaknesses may still exist in shallow snowpack areas. These weak areas appear to be on north-northeast aspects in the alpine. If the winds shift direction over the next few days, watch for new wind loading on south-west aspects.

Avalanche Problems

Storm Slabs

Deep storm slabs (50-60cm) may take some time to settle and bond to the old surface. This problem may linger in areas with a hard rain crust below the storm snow.

Use caution in lee areas. New snowfall mixed with wind loading will create slabs.Minimize exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Cornices

Fresh cornice growth may be large and fragile. Cornice falls may release storm slabs, or step down to deeply buried weak layers resulting in large avalanches.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Extra caution needed around cornices with current conditions.

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

Elevations: Alpine.

Likelihood: Likely

Expected Size: 1 - 3

Deep Persistent Slabs

There have been two natural deep persistent slab releases in the past two days in the Lizard range. Both of these avalanches were on northeast aspects in the alpine, and released to size 3.0 or larger.

Be aware of the potential for large, deep avalanches.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 2 - 4