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Archived

Avalanche Forecast

Dec 18th, 2018–Dec 19th, 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
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
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: Cascades - South East.

Dangerous avalanche conditions have developed. Heavy snowfall and strong wind have added a substantial slab to a known weak layer. Safe travel through avalanche terrain will warrant cautious route finding.

Discussion

Discussion 

Persistent weak layers have been identified in the adjacent East Slopes Central forecast zone. Although we have no information about snow conditions from this zone, the Persistent layers are likely to exist here as well.

Avalanche danger may be slightly mitigated due to low snow conditions below treeline, but coverage is rapidly increasing. 

Check the adjacent zones for more information that may pertain to this area.

Forecast Schedule

General avalanche and snowpack information will be provided during the winter. However, at this time we do not have enough specific snowpack information to issue an avalanche hazard rating for the East Slopes South zone.  

Snowpack Discussion

Regional Synopsis: December 18, 2018

Why has the avalanche danger been so high for so long? Two reasons: A very active and wet weather pattern and widespread persistent weak layer.

For perspective, the approximate snow totals from 12/9-12/18 are:

  • Mt Baker: 93”

  • Washington Pass: 45”

  • Stevens Pass: 66” mid-mountain

  • Snoqualmie Pass: 59” mid-mountain

  • Crystal Mountain 57” Green Valley

  • Paradise: 70”

  • Mt Hood Meadows: 37” mid-mountain

  • Olympics: 20”

In many areas, a layer of buried surface hoar and/or weak sugary facets was buried on December 9th. This layer has been the cause in numerous natural, explosive, and skier triggered avalanches. As this layer gets deeper it gets harder to assess … in short, the scenario is tricky and getting more dangerous by the day.

Higher snow totals along the Hwy 542 corridor /Mt Baker area have driven several avalanche cycles during this period. Loading from recent storms has been more incremental to the east and south and we have not yet experienced a widespread cycle …

When will we reach the breaking point? It’s hard to say. What we do know is we have a deep weak layer, reports of very large explosives triggered slides at Mission Ridge and Crystal Mountain, and more storms on the way.

Be patient and continue to stick to lower angle slopes with nothing above you.  This is a good time to avoid areas where avalanches can start, run, and stop.

We’d like to thank all of you who have sent NWAC your observations. If you are out in the mountains, let us know what you see.

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