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
Wed, February 5th, 2020 - 7:00AM
Expires
Thu, February 6th, 2020 - 7:00AM
Forecaster
Ryan Van Luit
The Bottom Line

The avalanche danger is CONSIDERABLE above 1,000′.  Human triggered wind slab avalanches are likely on steep slopes with previous or active wind loading.  If triggered, these wind slabs have the potential to overload buried weak layers and initiate a larger slab avalanche. Where wind slabs are not present, it’s possible for a person to trigger a large slab avalanche on one of the persistent weak layers 2-3′ within the snowpack.  Select routes with care and adjust as warranted.  Read the full forecast for reports of avalanches yesterday.

Thanks to our sponsors!
Wed, February 5th, 2020
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
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

Yesterday we had two reports of human triggered avalanches in the Turnagain Pass region and one near Summit Lake.  No one was injured.

The avalanche reported near Summit Lake was a slab avalanche that failed on facets over a crust.  The crown was estimated at 11-18″ thick and 80′ wide, with a  40′ vertical run.

Another avalanche was on Sunburst, where an anonymous skier reported triggering a wind slab on a west facing slope.  The avalanche was estimated to be 140′ wide, range in thickness from 1-2′, and ran 100′ vertical.  The bed surface was reported to be a layer of facets.  No one was caught or buried.

The other report was from 2nd Bowl, also known as Jr’s Bowl, off Seattle Ridge.  This snow machine triggered slab avalanche was on a northeast aspect at 2000′ and reported to be approximately 300′ wide, running 600′ vertical.  The crown depth was about 2′ thick and ran on small facets.  It’s important to note that one section of the avalanche triggered avalanches on both sides of the first.  No one was injured.

As snow enthusiasts, it’s incredibly valuable to share these experiences with the community.  We’re grateful to the parties involved for reporting this information, and for the positive outcomes.

Avalanche with trigger point. The middle released first, then the right slide, then the left.  2.4.2020 . Photo J. Davis

 

Small features can pile debris into terrain traps.  2.4.2020 . Photo J. Davis

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

Today calls for mostly cloudy skies and temperatures ranging from the 20’s to 32°F.  A trace of snow is possible today with calm to light southwest winds.  With relatively calm and temperate conditions, our snowpack will continue to adjust and settle.  Right now, the structure of the snowpack is fairly similar throughout the Turnagain pass area, but the stability can vary from one slope to the next. Yesterday, we had three reports of human triggered avalanches.

Where wind slabs exist on steeper slopes, it could be easy and likely for a human to trigger an avalanche. With the scope of the advisory area, it’s unreasonable to generalize which slopes have wind effected conditions right now.  This is where your awareness and on-site observation plays a critical role in making wise terrain choices. It’s essential to look for clues where wind slabs are forming, or have already formed.

Signs a wind slab could exist include:

  • Pillowed features (see photo below)
  • Visual signs of winds depositing snow onto the lee of ridges or gullies
  • Scoured exposed areas can indicate loading to the leeward side
  • Stiffening of the snowpack
  • Rippling on the surface
  • Shooting cracks
  • Hollow drum-like sounds in the snow

If you encounter these conditions don’t hesitate to adjust your route or plan.  This is a time to choose routes with intention, and dig/test/interpret the snowpack if that’s a skill-set you possess.

If you’re up for some reading, consider Roger Adkins paper discussing decision making and strategic mindset.

Pillowed wind features on SW aspect of Tincan, Hippy Bowl.  2.4.2020 . Photo: H Thamm

 

Cornices:  As always, give cornices a wide margin.

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

Our snowpack structure contains weak layers formed in January, before the storms last week.  Our testing shows these layers are becoming more stubborn but still possible for a human to trigger a large avalanche in these layers 2-3′ down in the snowpack.  Yesterday An observer suspected an avalanche was initiated within one of these layers.  With time and our current warming trend, the chances increase for the top 2′ of snow to consolidate and become more cohesive.  Current and trending warmer temperatures could create a more distinct slab above these weak layers.

Additionally, If a wind slab is triggered, it could step down to initiate one of these layers deeper within the snowpack.

Loose Snow Avalanches:  On steep slopes with unconsolidated snow, watch for easily triggered loose snow sluffs.

 

 

Weather
Wed, February 5th, 2020

Yesterday:  Mostly cloudy skies with a high near 30°F and low around 23°F. Winds were out of the Southeast from 5 -20 mph. A trace of snow accumulated.

Today:  Mostly cloudy skies today and high temperatures reaching toward 32°F.  A trace of snow is possible with calm to light southwest winds.

Tomorrow:  Mostly cloudy skies with a high near 29°F. Winds will be 5  -15 mph out of the southwest shifting to easterly.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28 1 0.1 56
Summit Lake (1400′) 27 1 0.1 20
Alyeska Mid (1700′) 29 1 0.05 56

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 ENE 9 30
Seattle Ridge (2400′) 26 ESE 6 18
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.