Share your feedback! Share your feedback!

How’s our new website?
How can we better serve you?

Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, January 6th, 2020 - 7:00AM
Expires
Tue, January 7th, 2020 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger remains MODERATE above 1,000′. The possibility remains for a person to trigger a large slab, up to 3′ thick, due to a buried weak layer. Slabs are most likely to be triggered in thin areas and may also be triggered after several tracks are on a slope. Additionally, watch your sluff, these are getting larger on steep slopes. As always, give cornices a wide berth and limit exposure under opening glide cracks.

Thanks to our sponsors!
Mon, January 6th, 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

Another large slab avalanche was triggered yesterday in our forecast zone; three others were triggered in Seattle Ck Drainage Friday and one on Fresno in the Summit Lake area Saturday. Yesterday’s slide was on the West face of Magnum (2,900′) and triggered by a skier at the top of the slope. The avalanche took out previous tracks and is believed to have released in a weak layer buried during Solstice. It was triggered at a thin spot in the slab that can be seen in the middle of the crown in the photo below. No one was caught and the skier was able to get off the slab at the top. A big thank you to the group for sharing their details and photos.

Looking up at the Magnum slide from yesterday, 1/5/19, West aspect, 2,900′. Note how the crown is thin in the middle, to the right of the skier in the photo. This thin area is where the skier reported to have triggered the slide. Photo from group involved.

Looking down from the crown at the debris, which covered previous tracks. Photo from group who triggered the slide.

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 the weather continues to be cold, calm and clear, triggering a large slab, similar to the one above, that breaks in weak snow 1-3′ below the surface remains our primary concern. Buried just over two weeks ago, during Solstice, was a layer of surface hoar and near surface facets. This layer now lurks between 1 and 3 feet below the soft snow surface and is still causing us grief as seen yesterday.

As long as this weak layer remains a concern, things to keep in mind:

  • Signs of instability are not likely to be present before a slope releases.
  • Thin areas are likely to be the trigger spots. For instance, on top of rollovers, near rocks protruding and areas that have seen past scouring by the wind.
  • It may be the 3rd or 10th person on the slope before someone hits the thin spot and triggers a slide.
  • Remote triggering a slab is possible, meaning from the top, sides or below.

Using good travel habits is key with this problem as it can be quite tricky. Exposing one person at a time, watching our partners, having escape routes planned and considering the consequences if the slope does slide are good ways to help stack the odds in our favor. For instance, avoiding slopes that end in terrain traps, where debris can pile up.


Snowpack at 3,000′ in Seattle Ck Drainage. Snow pit tests showed this weak layer took a lot of force to fail, but once it failed, slid easily. Less force is needed in thinner sections of the slab however.  See VIDEO

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

The cold temperatures are faceting and loosing the surface snow more and more each day. Sluffs have been reported to be getting larger on steep sustained slopes. Watch your sluff.

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 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.

Cornices:  Avoid traveling on cornices and limit exposure when passing beneath. Even with the cold benign weather, they can still be teetering on the brink of failure and break farther back than expected.

Weather
Mon, January 6th, 2020

Yesterday:  Cold and clear weather prevailed again yesterday. Temperatures were in the minus single digits in most valley bottoms and low elevations while bumping to 0F or just above along ridgelines during the day. Winds remained light from the West.

Today:  Cold, calm and clear weather remains in place. This morning, ridgetop winds are light and variable and temperatures are in the minus single digits at most locations. Ridgetop winds are forecast to turn westerly today and blow 5-10mph. Temperatures are expected to remain in the -10 to 0F range through the day and into tonight.

Tomorrow:  The current cold and clear pattern looks to continue well into the week. There looks to be the potential for some stronger northerly winds on Wednesday, stay tuned!

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) -3 0 0 39
Summit Lake (1400′) -12 0 0 14
Alyeska Mid (1700′) -1 0 0 36

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) -1 W 7 19
Seattle Ridge (2400′) 0 var 2 4
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

Subscribe to Turnagain Pass
Avalanche Forecast by Email

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.