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Archived

Avalanche Forecast

Dec 16th, 2018–Dec 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
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
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
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Glacier.

Rising temp's and strong winds are promoting wind slab development. These slabs are likely to be triggered by human loads. Stick to conservative, supported terrain.

Weather Forecast

Today will bring rising freezing levels (1600m) and moderate to strong SW winds. A pulse of snow should arrive tonight, bringing 10cm. Monday should be slightly cooler with flurries, but winds will increase to strong from the SW. More snow on Tuesday; 25cm with strong SW winds and freezing levels rising to 1400m.

Snowpack Summary

Extreme S winds on Saturday morning created wind slabs in the alpine. The December 9th persistent weak layer (surface hoar, sun crust and facets) is buried 60-100cm and is reactive where the overlying slab is dense. The November 21st persistent weak layer is down 120-160cm. Height of snow at treeline is approx 2m, and 1m at Rogers Pass.

Avalanche Summary

An extensive natural avalanche cycle occurred early Saturday morning, correlating with the high to extreme winds measured at that time. Numerous avalanches from sz 2 to 3's were observed both east and west of the summit from all aspects. A skier-triggered sz 1.5 avalanche off a gully sidewall partially buried one person in NRC Gully Saturday.

Confidence

Due to the number and quality of field observations

Avalanche Problems

Wind Slabs

Extreme southerly winds redistributed the storm snow Saturday. Wind slabs will be present on lee and cross-loaded features in the alpine/tree-line, and easily triggered on unsupported convex rolls. These slabs sit atop existing storm instabilities.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Avoid convexities and unsupported features.

Aspects: North, North East, East, West, North West.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1.5 - 2.5

Persistent Slabs

The December 9 weak layer is down 60-100cm. This layer consists of surface hoar, facets, and sun crust, depending on the aspect. Natural and human triggered avalanches are still occurring on this layer.
Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3.5