Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, November 26th, 2021 - 7:00AM
Expires
Sat, November 27th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains CONSIDERABLE at the higher elevations, above 2,500′, on all aspects. Human triggered slab avalanches, 2 feet deep or more, are likely on slopes 35 degrees or steeper. This is due to weak snow underlying the new settled snow from the past several days. Avalanches could be triggered remotely (from the bottom, side or above a slope). Careful route finding and conservative decision-making is essential.

At elevations below 2,500′, the danger is MODERATE where triggering a large slab avalanche, as described above, is possible.

Special Announcements
  • TODAY is White Friday at Powder Hound!! Swing by for that perfect holiday gift or those new skis – 10% of all proceeds will benefit the Chugach NF Avalanche Center, woot! Thank you, Powder Hound, for your long standing support.
  • The Turnagain Pass motorized area will open on Saturday, Nov 27th. *Snowmachiners: We have little information for Seattle Ck Drainage – avalanche danger exists. Easing into terrain and being wary of steep slopes is recommended – let’s have a safe 2021 opener!
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Fri, November 26th, 2021
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

It is the old sugary snow with various layers of buried surface hoar that is sitting under all the new wonderful fluffy snow that’s the problem. At the lower and mid-elevations, it’s hard to discern that there would be any funny business 2-3′ below our feet – but unfortunately there is. In many areas folks have been traveling, that 2-3′ of new snow has been so light it’s just making for great powder turns and deep wallowing. But, as we found yesterday, getting into areas at the higher elevations and where the winds blew prior, the new snow isn’t as loose and is just cohesive enough to be a slab sitting on a weak layer. In short, the weak layer is guaranteed. It’s whether or not the snow on top is behaving like a slab. If so, we have a good chance at triggering a large avalanche, up to 2′ or more in depth if the slope is steep enough.

Paying close attention to any whumpfing in the snowpack or cracks in the snow surface that shoot out from us will be our main clues we’ve found a slab. Yesterday on Seattle Ridge my partner and I ventured to an area that had some wind effect several days ago and had not been traveled since the new snow. We had several large wumpfs and shooting cracks; it was a no brainer for us to stick to the more mellow slopes at that point. That said, there are slopes not showing these signs, mostly below the treeline, and it can be tough to know what is safe and what is not. When in doubt, we can just stick to slopes under 35 degrees with nothing steeper above us.

Safe travel protocols are key if choosing to get into steeper terrain. This is exposing only one person at at time, watching our partners closely, having an escape route planned if the snow does move.

Some other things to consider as we head into several days of clearing weather:

  • This issue is more pronounced in the higher elevations.
  • There is significant uncertainty in areas less traveled and in the motorized zone of Seattle Creek drainage (heads up to the snowmachiners this weekend).
  • Settlement can create a slab as the days go by. This is why it could be possible to trigger a slab in the mid and lower elevations. The caveat being, clear and cold weather should help keep the snow loose.
  • If traveling along a ridgeline, know that you could trigger an avalanche from above. Be aware of other groups that could be below you and in the path if that were to happen.

 

Area of large collapse (whumpf) and subsequent shooting cracks. This shooting crack was excavated to see where the weak layer was. Minus 1 Bowl (Warm-up Bowl) on Seattle Ridge 11.25.21.

 

To recap quickly storm totals (estimated due to precipitation sensors not always reporting data). This is from Monday night through Thanksgiving.
Turnagain Pass:  3o-34″ north end of Pass, 18-20″ south end
Girdwood Valley:  28 – 34″ storm total
Summit Lake:  3-6″ storm total

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

A handful of glide cracks are still opening around the region. We have not heard of a release into an avalanche for several days now, but we should still watch for cracks and limit any time under them as they truly are unpredictable and unsurvivable.

Weather
Fri, November 26th, 2021

Yesterday:  Mostly cloudy skies with light snowfall here and there. Some clearing in the afternoon. Ridgetop winds were calm to very light from the northwest. Temperatures were in the 5-15F range.

Today:  Mostly clear skies with some valley fog possible today. Ridgetop winds could bump up to 15mph from the northwest at times, but should remain mostly light in the majority of the forecast area. Temperatures are cooling back into the minus single digits at high elevations and the single digits in valley bottoms.

Tomorrow:  Mostly sunny conditions are in store for the weekend, with possible valley fog. The northwest ridgetop winds look to remain fairly light as of now (5-15mph). Temperatures will also remain cold – single digits.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 12 5* 0.3* 64*
Summit Lake (1400′) 8 0 o 11*
Alyeska Mid (1700′) 12 N/A* N/A* N/A*

* Precipitation sensors are struggling to accurately capture the snowfall totals from the past few days.

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 6 W 4 14
Seattle Ridge (2400′) 6 N 3 10
Observations
Recent Observations for Turnagain Pass
Date Region Location
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Riding Areas
Updated Sun, November 27th, 2022

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass
Closed
The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.

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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.