Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 14th, 2021 - 7:00AM
Expires
Wed, December 15th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is a scary MODERATE for all aspects and elevations. Triggering either a lingering wind slab or a larger and more dangerous slab (scary) breaking in buried weak layers is possible. Wind slabs are likely to be found in exposed areas above treeline. A larger slab, which could break 3-5′ deep, could be triggered in the trees as well as in the Alpine. These may give us no sign a slope is unstable, be triggered from below, the top or the sides of a slope, and result in a deadly avalanche. Pay close attention to your terrain, know your safe spots and watch your partners.

SUMMIT LAKE: Strong NW winds hit this area hard on Sunday. Stiff wind slabs over a shallow and unstable snowpack is a big concern for triggering slab avalanches. Cautious route-finding is recommended.

SNUG HARBOR/LOST LAKE: Strong NW winds also hit the central and southern Kenai on Sunday. Old hard wind slabs sitting on an unstable snowpack can be expected. A very cautious mindset is recommend as dangerous slab avalanches could be triggered by people.

Special Announcements
  • AK DOT&PF:  There will be intermittent traffic delays today (Tuesday, December 14) from mileposts 90 to 100 on the Seward Highway, between Girdwood and Bird Creek, for Avalanche Hazard Reduction work. Motorists should expect delays of up to 45 minutes between 10am and 3pm. Updates will be posted at 511.alaska.gov.
  • Get your application in tomorrow! There is one day left to apply for an avalanche education scholarship through the Friends of the Chugach Avalanche Center. Deadline is December 15. Click HERE for details!
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Tue, December 14th, 2021
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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)
Recent Avalanches

There were no known avalanches yesterday. The last avalanches were two days ago on Sunday and related to the strong NW winds. Two of those were on the south end of Seattle Ridge.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

There are two main avalanche issues to deal with right now. The first is fairly easy to identity and are winds slabs from the past few days. The second, is not so easy, and related to the buried weak layers discussed in Problem #2.

Wind Slabs:  Although the NW winds got to much of the mountains on Sunday, it does appear that portions of Turnagain Pass were spared. Additionally, there was a bump in easterly wind yesterday that was able to move some snow around. This means we have to be on the lookout for the classic wind slab signs. Those are wind texture and signs of loading on the snow surface, cracking in the snow around you, and feeling for stiffer snow over softer snow.

Wind slabs in the Summit Lake area and other places that really saw the brunt of the NW winds could be quite stiff and large. They could be sitting on weak snow and not likely to heal very quickly. Any wind slab is likely overlying a weak snowpack in general and that is a double concern. With this setup, a smaller wind slab can release only to trigger a larger, much more dangerous, slab.

 

Looking east from the lower Eddies ridge- snow blowing off the ridgeline back toward Kickstep yesterday. 12.13.2021.

Avalanche Problem 2
  • 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

We are entering into a ‘scary MODERATE’ avalanche danger with respect to the buried weak layers we have talked about for a month now. This means those layers of facets and buried surface hoar are still there, we know it, but they are buried more deeply and are becoming harder to trigger. A scary MODERATE basically means we could start getting away with being on steeper slopes, but maybe not always, and if not, the consequences could be deadly. This is not a fun situation.

The weak layers are generally becoming one layer of faceted snow between 4-12″ thick depending on your location. They are anywhere from 3 to 5 feet deep, shallower in the Summit Lake area. The mid-elevations (1,500 to ~3,000′) have been the most reactive and this is likely because there is the old Halloween crust right under the facets. Open areas in the trees are also showing they are a concern. See the photo below from Seattle Ck drainage.

If you are choosing to start stepping into larger terrain, knowing that you could trigger a large slab is critical and slopes that have seen little to no traffic this season are more likely to avalanche. Watching your partners closely, only exposing one person at a time, and having an escape route planned are all ways to help hedge your bets. Also, thinking about the consequences if the slope does slide; will the debris pile up deeply in a terrain trap or spread out? It’s always better to avoid terrain traps.

If you’d like to just play it safe and avoid the issue all together, there is plenty of fun to be had on slopes less than 30 degrees with nothing steeper above you.

Photo highlighting potential for slabs in the lower terrain in/near the trees. Seattle Creek drainage – north end on the west side (east facing slope) just above Turnagain Arm. Natural avalanches from Thursday 12.9.21.

Weather
Tue, December 14th, 2021

Yesterday: Partly sunny skies were over the region yesterday with very cold temperatures (single to minus single digits). Ridgetop winds were generally easterly in the 5-10mph range with gusts into the 20’s. A few clouds moved in late in the day and a trace of snow has fallen overnight.

Today:  Cloudy skies and a chance for a few flurries this morning before skies are expected to begin to clear. Ridgetop winds have backed to the NW where they should remain in the 5-10mph range. Temperatures that rose to 5-10 above overnight, will fall again through the day back to the single digits.

Tomorrow:  Mostly sunny skies are in store for tomorrow with slightly warming temperatures (5-15F). Ridgetop winds look to be light and variable. Weather models are showing the chance for another system to push in on Thursday, it doesn’t look too potent at this point, maybe a few new inches.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 4 0 0 75
Summit Lake (1400′) -10 0 0 23
Alyeska Mid (1700′) 2 trace 0.01 46

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 0 NE 9 24
Seattle Ridge (2400′) 3 SE 6 18
Observations
Recent Observations for Turnagain Pass
Date Region Location
11/26/22 Turnagain Observation: Eddies
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Sunnyside / Seattle Ridge
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Tincan Trees
11/25/22 Turnagain Observation: Tincan
11/25/22 Turnagain Observation: Top of Seattle Ridge uptrack
11/24/22 Turnagain Avalanche: Sunnyside/Main Bowl
11/23/22 Turnagain Avalanche: Seattle Ridge
11/23/22 Turnagain Observation: Tincan Trees
Riding Areas
Updated Sat, November 26th, 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.