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Archived

Avalanche Forecast

Nov 28th, 2020–Nov 29th, 2020
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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.

High quality skiing and riding has been found this week. Continue to choose your routes carefully and test for triggerability before dropping in. Large natural avalanches have been running to valley bottom

Weather Forecast

A brief ridge of high pressure is forecast to bring clear spells and high temperatures of -9 today and -5 and cloudy tomorrow. A cold front is due to pass through on Monday bringing another 10cm of snow, falling freezing levels and strong SW wind.

Snowpack Summary

An additional 15cm overnight now makes 60 cm of storm snow over old snow and the Nov 23 surface hoar size 3. The surface hoar has been observed at treeline in isolated areas but in some other profiles has not been found. The Nov 5 crust is now between 90 and 140cm down which is within the triggerable range for skiers and snowboarders in some areas.

Avalanche Summary

3 large natural avalanches were detected early this morning by IDA. A skier triggered sz 1.5 on surface hoar in Avalanche Crest yesterday was reported using MIN. A sz 2.5 on Thursday also failing on SH with wide propagation was reported from just outside the park. Numerous new natural slides in the HWY corridor this week mostly sz 2 with a few sz3s

Confidence

Due to the number of field observations

Avalanche Problems

Storm Slabs

60cm of storm snow fell over the last 3 days with Mod-Strong SW winds. This will be more reactive at treeline where it overlies the Nov 23 surface hoar sz 3-5mm

  • Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.
  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2.5

Persistent Slabs

Steep planar slopes should be avoided, especially at and just above treeline. Recent natural/human triggered avalanches, snowpack tests, and reports of whumphing indicate that this layer may still be triggered by the weight of a skier.

  • Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3