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 31st, 2021 - 7:00AM
Expires
Mon, February 1st, 2021 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger will be MODERATE above 1000’, where it will be possible to trigger a wind slab avalanche up to a foot deep. Light winds have been able to drift the 8-10” of low-density snow at the surface into sensitive slabs on top of fragile weak layers that formed earlier in the week. These sensitive wind slabs exist on some, but not all, slopes. Today it will be important to recognize and avoid wind-loaded terrain.

The avalanche danger will be LOW below 1000’, where less soft snow at the surface and a virtual lack of wind will make avalanches unlikely.

PLACER/PORTAGE VALLEY/WHITTIER: This area received 12-18″ snow with the most recent storm, and has seen more wind in the past few days. This will make larger avalanches possible, and extra caution is advised.

LOST LAKE/SNUG/SEWARD: These areas also received more snow than the Turnagain/Girdwood/Summit areas. With 20-30 mph winds expected today, avalanche conditions may be more dangerous here than in our core advisory area. Cautious route finding will be essential in these zones.

 

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Sun, January 31st, 2021
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

We received multiple reports of skier and snowboarder-triggered storm and wind slab avalanches yesterday. Most of these were not big enough to bury a person, but they did grab our attention. Nobody was caught or carried in any of these avalanches.

  • Lynx Creek/ Captain’s Chair: A group changed their objective after triggering multiple soft slab avalanches on their approach to Captain’s Chair.
  • Tincan: Skiers triggered multiple small slab avalanches on convex rollovers on a SW aspect. They both appear to be in slightly wind-loaded pockets.
  • Eddies: A snowboarder triggered a small soft slab on the upper west face of Eddies.
  • Seattle Ridge: Skiers triggered multiple small wind slabs in the Seattle Ridge back bowls, and a snowmachine triggered a small wind slab on the front side.
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

In the past two days, we have gotten reports of several human-triggered avalanches failing on the interface between the most recent storm snow and a weak layer of buried surface hoar and near-surface facets. Most, if not all, of these avalanches have occurred on slopes that had seen recent wind loading. Similar activity will be the main concern for today. We are not expecting to see any extraordinary winds during the day, but it will not take much to move the low-density snow on the surface into sensitive slabs. If your travel plans for the day involve any kind of steep terrain, it will be important to pay attention to changing conditions at the snow surface. Even a subtle increase in surface hardness could be enough to make a dangerous combination of a slab on top of very weak snow. Be on the lookout for red flags indicating increasing instability, such as shooting cracks and fresh avalanche activity. The most likely places to find unstable snow today will be near ridgelines, below convexities, or on cross-loaded slopes. With winds forecast out of the west, we might see slabs forming in unusual places today.

Sluffs: The low-density snow at the surface has been producing sluffs in steep terrain. These avalanches are not big enough to bury a person, but they could have serious consequences if they carry you into terrain traps like cliffs, trees, or rocks. If you plan on heading into steep terrain, be aware of these dry loose avalanches, and of exposure to consequential terrain below.

Cornices: We have recently seen large cornices peeling away from ridgelines, opening up large cracks (there are some good photos here). Be sure to give them plenty of space, and minimize the amount of time you spend below them.

Small skier-triggered avalanches on the SW aspect of Tincan yesterday. Photo: Adam Rothman. 01.30.2021

Cornices are starting to peel away from ridgelines, opening up large cracks. These cracks can sometimes be difficult to identify when they get bridged with blowing snow. Bertha Creek Headwall. Photo: Tony Naciuk. 01.30.2021 

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

We have been seeing more glide cracks open up recently. Glide avalanches are large and destructive, and their timing is impossible to predict. Avoid traveling on or below slopes with glide cracks, and let us know if you see any new ones open up.

Weather
Sun, January 31st, 2021

Yesterday: Winds were calm to light, blowing 0-10 mph at ridgetops. High temperatures were in the upper teens to low 20’s F, with lows in the single digits to low teens F overnight. We saw plenty of sunshine and no precipitation under clear skies.

Today: Similar weather continues today, as an upper-level ridge of high pressure stays in the area. We expect to see temperatures reach the low to mid teens F, with light winds 5-10 mph out of the northwest. We should see another sunny day, with no precipitation expected.

Tomorrow: Lows will drop down into the single digits tonight, and stay around 10 F tomorrow. Light westerly winds will continue, with another day of clear skies expected. No precipitation is expected tomorrow.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) N/A* N/A N/A N/A
Summit Lake (1400′) N/A N/A N/A N/A
Alyeska Mid (1700′) 16 0 0 109

*Snotel sites are not reporting as of 6:45 a.m.

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 12 W 6 13
Seattle Ridge (2400′) 13 NE 3 8
Observations
Recent Observations for Turnagain Pass
Date Region Location
03/06/21 Turnagain Observation: Eddies/Tincan
03/05/21 Turnagain Observation: Seattle Ridge – SE face, road side
03/05/21 Turnagain Observation: Tincan, north side
03/04/21 Turnagain Observation: Magnum Peak
03/02/21 Turnagain Observation: Pastoral
03/01/21 Turnagain Observation: Tincan
02/28/21 Turnagain Observation: Lynx Creek
02/28/21 Turnagain Avalanche: Tincan
02/28/21 Turnagain Observation: Eddies
02/25/21 Turnagain Observation: Seattle flats, above power line
Riding Areas
Updated Fri, February 12th, 2021

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
Open
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Open
This area will close to machines on April 1 as per CNF Forest Plan. Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Turnagain Pass
Open
Twentymile
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Summit Lake
Open

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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.