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West Slopes North - Canadian Border to Skagit River

Issued: 6:00 PM PST Thursday, December 13, 2018
by Dallas Glass

Avalanches are continuing to occur and more precipitation is on the way. It will be very dangerous in the backcountry Friday. Stay away from anywhere avalanches can start, run, or stop, including flat areas with steep slopes above.

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Avalanche Summary

Many natural and triggered avalanches were reported from the Baker area Thursday. Some of these were very large and destructive. This is the fourth straight day we have had avalanches reported in this region. This avalanche cycle has been and will continue to be very dangerous. Avalanche observations like this are the easiest information to understand. This is a good time to dial it way back.

Avalanche Problems for Friday

Persistent Slabi

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Persistent Slabs can be difficult to assess and predict. We need to give them a high level of respect and stay well away from avalanche terrain. In the Baker area 4-6 feet of settled snow now sits atop a layer of weak sugary facets and/or buried surface hoar. If you trigger this layer a resulting avalanche may be very large and destructive. Persistent Slabs avalanches can sometimes act in surprising ways. You may be able to trigger these avalanches remotely. Avalanches can travel down into flat terrain and lower elevation bands.

 

Regional Synopsis 20181213

Winter is here.

A productive winter storm pattern has elevated the avalanche danger and provided an interesting start to the season.  

A quick breakdown:

  • Tuesday and Wednesday saw a significant localized avalanche cycles.

  • We have a lot of new snow...2’ to 5’ above 4500ft.

  • We’ve gotten a lot of wind.

  • We have weak layers near the ground.

Dangerous avalanche conditions will persist over the next couple of days. That said, it is early season and the flavor of avalanche you may run into is likely a function of elevation, timing, and dumb luck.

Here are some basic emerging patterns:

  • Snowfall totals so far this week (Monday morning to Thursday evening) illustrate more recent snowfall in the north than the south:

    • Mt. Baker: 55”

    • Washington Pass: 29”

    • Stevens Pass: 37”

    • Snoqualmie Pass: 28”

    • Paradise: 38”

    • Mt. Hood Meadows: 13”

  • Upper versus Lower Elevations: The change in the snowpack is still pretty dramatic with elevation. Height of snow decreases rapidly below 4500’ at Baker and Washington Pass, 5500’ at Crystal/Rainier. The Passes have better low elevation coverage, but it's still pretty thin below 4000’. With additional warm storms in the forecast, this pattern is expected to continue for awhile.

  • East versus West: Loading along the East slope has been more incremental, and a  variety of buried facet and surface hoar layers may be found. This is most pronounced near WA Pass. Although significant snowfalls and precip totals have resulted in thicker, more homogeneous snowpack in the western zones, lingering weak layers near the ground will persist through the week.

The uncertainty of how reactive our buried weak layers are will carry into the weekend. Be cautious and get home safe.

 

No Corresponding Mountain Weather Forecast Available
This information is provided by the U.S.D.A. Forest Service and describes general backcountry avalanche hazard and conditions. It does not apply to ski areas and highways where avalanche mitigation is conducted. Read more here.