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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, January 5th, 2020 - 7:00AM
Expires
Mon, January 6th, 2020 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is MODERATE above 1000′.  Triggering a large avalanche breaking on buried weak layer 1-3′ deep in the snowpack remains possible today.  Watch out for sluffing in steep terrain. Choose slopes carefully with the consequences of an avalanche in mind. Use good travel protocol, give cornices a wide berth and limit time under glide cracks.

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Sun, January 5th, 2020
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
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
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Heads up if traveling in Summit Lake just south of Turnagain Pass. We received a report of a large human triggered avalanche on Fresno Peak in Summit Lake yesterday. We are currently gathering more information about it. Observers on Friday found the Solstice layer of buried surface hoar on Colorado Peak just south of Fresno.

Friday three avalanches were triggered in Main Bowl. All are suspected to have failed on the Solstice buried surface hoar layer. The avalanche pictured below was large enough to injure/bury a person.

Main Bowl, SE Aspect. ~2300’. Snowmachine triggered, ~300’ wide. Debris 10-15’ deep. Photo: G. Predeger

Avalanche Problem 1
  • 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

Although many people are skiing and riding steep terrain without incident, the possibility of triggering a large avalanche remains due to buried weak layer. Surface hoar and faceted snow that formed just before the Solstice is now buried 1-3′ deep and has proven reactive in the 3 snowmachine triggered avalanches in Main Bowl Friday and in some snow pits across the region. This is also the suspected weak layer in the reported human triggered avalanche in Summit Lake yesterday. This is out of the advisory area but is a popular spot to recreate and the snowpack is generally shallower. Conditions often can be very similar in Lynx Creek and around the Silvertip, Twin Peaks zone.  This lingering possibility of triggering a large avalanche should be part of how you plan your day in the mountains. Ease into steeper terrain, think about slopes as avalanche paths and imagine where the snow would end up if it did slide. The consequences of being deeply buried in a terrain trap should be a consideration. There is a supportable crust from the New Years Day rain up to 2300′-2500′. Triggering an avalanche is possible where the crust is very thin and then up in elevation from there. There is very stiff snow (slab) over the buried weak layer and that is covered by the soft snow from New Years. Signs of instability will mostly likely not be present at this point and it might not be the first person on the slope that triggers the avalanche. There were previous tracks on the slope in two of the Main Bowl avalanches Friday.

The Solstice buried surface hoar layer found in a pit on Eddies at 2500′ yesterday, 1.4.20. Here it was found just over a foot down. 

G. Predeger investigates the buried surface hoar in the crown of the snowmachine triggered avalanche in Main Bowl, Turnagain Pass. Here the weak layer was buried 2-3′ deep. 1.3.20. Photo: Chris Yelverton

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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

Low density surface snow in steep terrain has the potential to be a loose snow avalanche a.k.a sluff. It’s important to think about sluff management as you choose your descent. Be mindful of consequences if you were to get knocked off your feet by a fast moving sluff in steep terrain.

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

Glide cracks:  Glide cracks continue to open with the cold temperatures which is another interesting factor with this unpredictable hazard. Limit time spent underneath glide cracks as they could release into a dangerous glide avalanche at any time.

Large glide crack on the north side of Cornbiscuit, 1.4.20. Photo: Allen Dahl

Cornices: Cornices can break farther back than expected. Avoid travel on them and limit your exposure when passing beneath.

Cornices on Magnum summit ridge, 1.4.19. Photo: Emily Sullivan

Weather
Sun, January 5th, 2020

Yesterday: Skies were partly cloudy with some patchy valley fog. Temperatures were in the single digits to below 0°F. Winds were light and variable. Overnight temperatures were generally below zero with a few stations dropping to the negative teens.

Today: Mostly sunny which some scattered clouds and patchy valley fog. Temperatures will be in the single digits. Winds will kick up slightly from the north, averaging 5-10 mph gusting into the teens. Overnight skies will be partly cloudy and temperatures will rise a few degrees as the clouds move in.

Tomorrow: Mostly to partly cloudy skies and a chance of scattered showers. Highs will be in the teens and upper single digits and winds will be northerly. Mostly sunny skies are back on tap for Tuesday and Wednesday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 2 0 0 40
Summit Lake (1400′) -7 0 0 14
Alyeska Mid (1700′) 3 0 0 35

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 2 W 4 17
Seattle Ridge (2400′) 0 N 2 12
Observations
Recent Observations for Turnagain Pass
Date Region Location
05/06/20 Turnagain Avalanche: Pastoral Peak, north face
04/10/20 Turnagain Avalanche: Wolverine
04/10/20 Turnagain Observation: Eddies lookers right shoulder
04/09/20 Turnagain Observation: Bench Peak
04/04/20 Turnagain Observation: Tincan
04/04/20 Turnagain Observation: Pete’s North
03/26/20 Turnagain Avalanche: Tincan – Proper (SW facing)
03/26/20 Turnagain Avalanche: Seattle Ridge
03/25/20 Turnagain Avalanche: Sunburst Uptrack @ 2000′
03/24/20 Turnagain Observation: Turnagain – Road Observations
Riding Areas
Updated Fri, May 01st, 2020

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
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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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.