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Archived

Avalanche Forecast

Dec 20th, 2018–Dec 21st, 2018
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
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.

Avalanche control today. All permit areas are closed. A perfect opportunity to go to the local ski hills!

Weather Forecast

Today, periods of snow (17cm) accompanied by moderate to extreme S'ly winds and freezing level expecting to rise to 1500m. Another 9cm forecast for tonight with winds shifting to moderate SW gusting to extreme. A cooling trend with light precipitation is expected for the weekend.

Snowpack Summary

30cm+ in past 48hrs, warm temp's, and moderate to strong winds are building reactive 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

10 avalanches recorded in the highway corridor east of Rogers Pass summit in the last 24hrs. Notably, three of these slides were size 3.5.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Storm Slabs

30cm+ of snow in the past 36hrs accompanied by mod S'ly wind and warm temp's, is forming a cohesive surface storm slab. Slabs will be more pronounced in wind effected areas such as immediate lee features below ridge crests and on cross-loaded slopes.
The new snow will require several days to settle and stabilize.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2.5

Persistent Slabs

The Dec 9 weak layer is down 70-100cm 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