Avalanche Forecast

Issued: Feb 22nd, 2017 3:47PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Cornices and Deep Persistent Slabs.

triley, Avalanche Canada

Lizard-Flathead.

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

Summary

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.

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

Valid until: Feb 23rd, 2017 2:00PM