Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, February 8th, 2017 - 7:00AM
Expires
Thu, February 9th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

There is a generally  LOW  avalanche danger in the Turnagain Pass region where triggering an avalanche in unlikely. However, there are areas above 1,500′ that have a  poor snowpack structure and there remains the possibility of triggering a large slab avalanche (2-5′ thick) that breaks near the ground;  this situation is keeping the danger  MODERATE. Likely trigger points are thin areas on a slope (i.e. where rocks are showing through) and likely triggers are large, such as groups of people, snowmachine(s), and cornice falls. Additionally, there are some normal caution problems to keep an eye out for today, these are: shallow fresh wind slabs, sluffs in steep terrain and cornice breaks.  

Summit Lake and Girdwood:   A poor snowpack structure  exists in these areas as well and human triggered avalanches breaking near the ground are possible. Make sure and check the Saturday Summit Summary  HERE.

*This is a  low probability but high consequence situation  and it is critical that safe travel protocols are executed and avalanche rescue gear is carried. This means only one person on a slope at a time – in the event an avalanche is triggered, there is/are people capable of rescue. Also, have escape routes planned and watch your partners.  These practices likely saved the life of a person fully buried near the Seattle Ridge Headwall on Friday, Feb 3rd.    Check out CNFAIC Near Miss Final Report from this incident  HERE.

Thanks to our sponsors!
Wed, February 8th, 2017
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)
Avalanche Problem 1
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

Sunshine and mostly stable snowpack conditions have allowed many people to test the slopes in the Turngagain pass area. However, if venturing out today it is important to remember there were two large and dangerous avalanches triggered on Friday HERE and HERE. The likelihood for someone to find and trigger a large slab is decreasing as the snowpack adjusts but the poor snowpack structure remains and the consequences are scary. It still important to be on guard and utilize safe travel protocol. 

We visited the site of the Lynx Creek avalanche (one of the avalanches that occured on Friday, 2.3.17) yesterday and were able to find reactive snow in our flank profile. We will put together a more detailed report this week. This avalanche was large, with crown close to 1000′ feet wide, running over 1500′ and debris depths over 10′ deep in many places. The crown depth varied from 1′-4′ thick. In some places it stepped down from a mid-pack weak layer of facets to a lower layer of facets over a crust. This was triggered in a thin spot, which is something we have been talking about with this variable and spooky deep persistent slab set-up. One is likely to have no signs of instability and there could be many tracks on a slope before an avalanche occurs. The reactive snow in snowpack tests yesterday is an indication that propagation potential still exists. 

This deep slab problem is tricky and the important thing is to know you may be on a slope with weak snow underneath a stiff slab 2-4+’ thick that just needs a trigger in the right spot. Again, likely trigger spots are where the slab is thin, possibly next to rocks. Likely triggers are large: snowmachines, groups of people or cornice falls. The poor snowpack structure will also be important to remember if and when we get another significant loading event. 

Crown in Lynx Creek avalanche (occured 2.3.17). Note where it stepped down. 2.7.17

Extended column test in flank profile adjacent to Lynx Creek avalanche. Full propagation at 11 taps on a layer of small facets sandwiched between two harder layers. In parts of this avalanche it stepped down below this to a lower layer of facets over a deteriorating melt-freeze crust. 

Additional Concern
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Cornices: This weekend cornice cracks were reported along the back bowls of Seattle Ridge making some of these cornices extra sketchy. A few chunks have been triggered this week. Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

Wind Slabs: An observer yesterday reported a period of light winds drifting snow onto leeward aspects. New shallow wind slabs may be tender, or it may still be possible to find an old stubborn wind slab on leeward slopes. Look out for pillowed or drifted snow and avoid areas with stiff snow over soft snow. 

Loose snow: With 4-8″ of loose snow on the surface over a dense base, watch your sluffs and watch how the sun is affecting the snow around you. 

Over the last few days the sun has been affecting the snow on Solar aspects (East – Southeast – South.) Small sun induced rollerballs and a few point releases have been observed as well as a sun crust on some Southern aspectsToday is forecasted to be cooler and cloud up. Expect to find the sun crusts on solar aspects. 

Cornice avoidance 2.7.17. Photo: Billy Finley

 Wind moving snow in Lynx Creek, 2.7.17. 

 

Sun induced roller balls and a glide crack in Lynx Creek, 2.7.17

Weather
Wed, February 8th, 2017

Yesterday was clear and sunny with valley fog. Temperatures were in the low 20Fs- high teens at ridgetops and single digits-low teens in the valley bottoms. Westerly winds were mostly light with a few gusts throughout the day.  Overnight temperatures were in the teens and single digits. Winds bumped up slightly overnight.

Today will start out mostly sunny with clouds developing throughout the day and a chance for flurries in the afternoon. Tonight will be mostly cloudy with a chance of snow. Tomorrow there is also a chance for snow. At this point this first system doesn’t look to be much of a snow producer. Colder air is forecasted to move over the area on Friday morning and there is a chance that will be combined with some snowfall but likelihood and amounts are not certain. The quote this morning from the National Weather Service is “One can say with high confidence  that several areas of low pressures will move into the Gulf of  Alaska this weekend through the middle of next week, but  confidence is low in the exact track of them.”  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 23   0   0   52
Summit Lake (1400′)  15 0    0 23
Alyeska Mid (1700′)  22 0  0 46

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  17 W   5   14  
Seattle Ridge (2400′)  20  SW-NW 5  16
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
Riding Areas
Updated Wed, December 11th, 2019

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.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

Subscribe to Turnagain Pass
Avalanche Forecast by Email