Archived

Avalanche Forecast

Nov 24th, 2015–Nov 25th, 2015

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

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: Glacier.

The Winter Permit System is in effect. Please ensure you have a valid winter permit and check to see which areas are open.

Weather Forecast

A strong push of Arctic air will pass through Rogers Pass today. Expect winds to increase from the N, with temp's dropping into the minus teens. Skies should clear late in the day and into tomorrow. By Thursday, strong inversions and valley cloud will be dominating the area, with warm alpine temp's and cool, cloudy valleys.

Snowpack Summary

20cm of storm snow is currently being redistributed by strong N winds. These storm slabs overlie a variety of surfaces, including suncrust on steep S-SW aspects, with 2-3mm surface hoar on most other aspects. Below this, windslabs appear to be bonding and the snowpack as a whole is strengthening. A weak basal layer exists on alpine N/NE aspects.

Avalanche Summary

A few isolated size 2 slabs have been observed from steep S-facing alpine terrain this morning. Several large (size 3) avalanches were observed in the Swiss Peak group over the weekend, so the weak basal layer on N/NE alpine aspects is not bonding well at the moment.

Confidence

Due to the number and quality of field observations

Avalanche Problems

Storm Slabs

The strong northerly winds today will redistribute the new snow, creating storm slabs on S aspects. These slabs will be touchy until they have enough time to bond to the underlying surface hoar or suncrusts.

Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Wind Slabs

Wind slabs will be hidden by the fresh snow. Extra caution should be used when transitioning into wind affected terrain.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3

Deep Persistent Slabs

On northerly alpine slopes, snow from early Sept was preserved and facetted forming a basal weakness. This may have been the failure plane on Swiss and Hermit Peak on the weekend.

Avoid shallow snowpack areas where triggering is more likely.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 3 - 4