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Archived

Avalanche Forecast

Dec 21st, 2018–Dec 22nd, 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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Now that we've dug ourselves out from that windy storm, sticking to well-supported, low-angled lines would be wise. Touchy cornices will be looming overhead like the mean ol' Grinch.

Weather Forecast

The storm has passed and the weather is settling today. We can still expect some flurries today, bringing gusty mod/strong ridge-top winds. Freezing levels will drop to the valley-bottom. Saturday and Sunday will see similar conditions, with light SW winds, alpine highs of -9*C, and isolated flurries between sunny breaks.

Snowpack Summary

50cm+ in past 72hrs, warm temp's, and strong winds have created reactive to touchy storm slabs. The Dec 9 surface hoar/facet/crust persistent weak layer is buried 90cm+ and is producing large whumphs and sudden planar results. The Nov 21 surface hoar/facet persistent weak layer is down ~140cm.

Avalanche Summary

A widespread natural avalanche cycle to sz 3-3.5 occurred last night with the strong/extreme SW winds. Artillery control during the day produced avalanches from sz 2 to 3.5 in the highway corridor.

Confidence

Avalanche Problems

Storm Slabs

50cm+ of snow in the past 72hrs, accompanied by strong SW winds and warm temp's, has formed a storm slab at all elevations. Slabs will be more pronounced in immediate lee features below ridge crests and on cross-loaded slopes. Human triggering likely
If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

The Dec 9 weak layer is down 80-110cm and consists of surface hoar, facets, and sun crust, depending on the aspect. Sudden planar results are being seen on this layer. Natural and human triggered avalanches are still occurring on this layer.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3.5