Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, March 24th, 2022 - 7:00AM
Expires
Fri, March 25th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche Warning
Issued: March 24, 2022 6:00 am
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line

The avalanche danger is HIGH at all elevations. A powerful storm is forecast to produce up to 30+” of snowfall across the forecast area over the next 24 hours, with 10-16″ of snow having already fallen over the past 24 hours. Human triggered avalanches 2-4′ deep are very likely and natural avalanches are likely, especially in treeline and alpine elevation bands. Several deeper layers of buried surface hoar exist in our forecast area which could cause very large avalanches with the added weight of the new snowfall. Travel in avalanche terrain is not recommended. Avalanches could runout to valley bottoms, so be aware of any slopes above you that have a slope angle of 30 degrees or more.

SUMMIT LAKE: A very weak snowpack exists in the Summit Lake area and the winds and new snow associated with this storm could produce very large avalanches on buried weak layers. Travel in avalanche terrain is not recommended. 

SEWARD/LOST LAKE/SNUG HARBOR: This storm will create high avalanche danger across the region including near Seward and Snug Harbor. Travel in avalanche terrain is not reccomended.

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Thu, March 24th, 2022
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Turnagain Pass

  • Pete’s North – Two skier triggered avalanches on a layer of buried surface hoar from 3.16 about 12-16″ deep and 75-100′ wide. The first avalanche was triggered as we were preparing to dig snowpits in a forested clearing on relatively low slope angles. The second was intentionally triggered on our descent in a slightly more open area adjacent to the first avalanche. The buried surface hoar was 3-6 mm grain size and very thick on this relatively protected slope near the top of treeline (see on here for more details).

Skier triggered D 1.5 on a layer of buried surface hoar from 3.16. Avalanche triggered while preparing to dig snowpits in a forested clearing at 2000′ on a W aspect of Pete’s N. Photo 3.23.22

Skier triggered D2 soft slab on a layer of buried surface hoar from 3.16, on a W aspect at 2000′ on Pete’s N in Turnagain Pass. Photo 3.23.22 

  • Tincan – Small storm slabs 8-10″ deep on steep rollover in Tincan trees. The new snow fell on top of surface hoar that was buried on 3.22 which is making storm slab more reactive than typical and possible to trigger on lower slope angles.

Small storm slabs in the 8-10″ of new snow that had fallen as of yesterday afternoon. Photo from Brooke Edwards 3.23.22

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

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

A powerful storm is impacting our area and has already deposited 10-16″ of snow, with another 30+” of snow possible in the next 24 hours. Strong winds averaging 25-50 mph with gusts up to 100 mph will accompany the snowfall and have been actively transporting snow into fresh wind slabs at upper elevations since yesterday morning. This is a massive load on top of a snowpack that contains three layers of buried surface hoar within the upper 2-3′ of the snowpack. Human triggered avalanches are very likely and natural avalanches are likely, and could step down to deeper weak layers to create very large avalanches (see problem 2 for more information). Travel in avalanche terrain is not recommended, including travelling on or underneath all slopes with 30 degree or higher slope angles. Avalanches from upper elevations could runout to valley bottoms so avoid travelling underneath any potential avalanche terrain.

The new snowfall will make storm slab avalanches in protected areas very likely for human triggering, especially since a layer of buried surface hoar exists just beneath the new snow which was buried on 3.22. In addition, wind slabs up to 2+’ deep are almost certain to be triggered in treeline and alpine elevation bands. We need to step back and give the mountains some breathing room as this storm impacts our region.

Active wind loading in treeline and alpine elevation bands throughout the day yesterday. Photo 3.23.22

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

There are three separate layers of buried surface hoar in our upper snowpack that have been responsible for numerous human triggered avalanches in the past few weeks. These layers were buried on 3.2, 3.16, and 3.22 respectively. The distribution is widespread in the Turnagain Pass and Seattle Ridge area including upper elevations. The weak layers have also been observed in Portage/Placer and Girdwood, but the distribution seems to be a little bit less widespread. Locating these layers of buried surface hoar can be tricky in a snowpit if they are not particularly well preserved. However, that does not mean you could not trigger an avalanche on these layers. Over the past two weeks many very experienced parties have been involved with human triggered avalanches on these weak layers which should be a reminder to give these weak layers a wide berth by sticking to lower angle terrain. With a massive new load of snow coming today it is likely that these older weak layers will reactivate and create very large avalanches up to 3+’ deep.

Yesterday on Pete’s N we triggered an avalanche on the 3.16 buried surface hoar while preparing to dig snowpits and evaluate stability. The avalanche propagated very widely and released the entire area of steeper terrain within a small opening in the trees. In our crown profile we found all three layers of buried surface hoar in the pit wall but only had propagating ECT results on the 3.16 layer that was also the weak layer for the avalanche. On our descent we were able to trigger another avalanche on the same layer on a similar feature that was in slightly more open terrain (see ob here). We recommend avoiding all avalanche terrain during the period of intense snowfall over the next 24-48 hours.

Buried surface hoar on the bed surface of a D 1.5 avalanche we triggered while preparing to dig snowpits at 2000′ on a W aspect of Pete’s N. Photo 3.23.22

Weather
Thu, March 24th, 2022

Yesterday: Mostly obscured cloud cover with a few periods of broken skies and small blue holes over Turnagain Pass. Heavy snowfall starting in the afternoon. Snowline down to sea level. Moderate winds a treeline elevations with enough strength to transport the soft surface snow. Strong winds at upper elevations with widespread wind transport. Temperatures were in the 20s at mid and upper elevations and low 30s at trailhead elevations.

Today: Heavy snowfall and strong winds. Snow intensity peaking between 6 pm tonight and 6 am Friday morning. Snowfall amounts up to 30″ possible over the next 24 hours.  Snow line is expected to move up to 800-1000′ this afternoon and evening. Winds averaging 25-50 mph with gusts possible up to 100 mph.

Tomorrow: Continued heavy snowfall and strong winds throughout the day tomorrow. Winds start to back off overnight of Friday and snowfall tapering off Saturday morning. Storm totals could be up to 36+” from Thursday through Saturday in Turnagain Pass and Girdwood. Higher snow totals likely in Portage and Placer areas. Snow line will remain

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 6 0.5 104
Summit Lake (1400′) 29 2 0.1 41
Alyeska Mid (1700′) 30 16 1.2 NA

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 ENE 26 70
Seattle Ridge (2400′) 24 SE 16 57
Observations
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Riding Areas
Updated Fri, May 13th, 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
Closed as of May 1 per Forest Plan.
Placer River
Closed
Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage
Closed
Closed as of April 1st per Forest Plan.
Turnagain Pass
Open
Open. Extended opening through May 31.
Twentymile
Closed
Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake
Closed
Closed as of May 1 per Forest Plan.
Lost Lake Trail
Closed
Closed as of May 1 per Forest Plan.
Primrose Trail
Closed
Closed as of May 1 per Forest Plan.
Resurrection Pass Trail
Closed
Closed as of May 1 per Forest Plan.
Snug Harbor
Closed
Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor
Closed
Closed as of May 1 per Forest Plan.
Summit Lake
Closed
Closed as of May 1 per Forest Plan.

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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.