Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, February 11th, 2017 - 7:00AM
Expires
Sun, February 12th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

There is a MODERATE avalanche danger in the Turnagain Pass area. Triggering a fresh wind slab in leeward terrain is possible. In protected areas triggering a shallow storm slab or loose snow avalanche is also a concern. In addition, keep in mind that  due to poor snowpack structure there is still a chance of  triggering a large slab avalanche (2′-5′ thick) that breaks near the ground.  

Summit Lake: Make sure and check the Saturday Summit Summary  HERE.

Thanks to our sponsors!
Sat, February 11th, 2017
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
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
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
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.
More info at Avalanche.org

The snow that fell yesterday was light and fluffy and the kind that will easily blow around and form tender wind slabs. Overall the winds weren’t strong but there was period of more sustained wind last night. The new snow fell on surface hoar, near surface facets and sun crusts and was not bonding well. This should make winds slabs easy to trigger but due to limited snow totals the slabs shouldn’t be that deep (6″-1′). Look for pillowed or drifted areas in leeward terrain and pay attention to shooting cracks. 

In areas not affected by wind there is also potential for shallow storm slabs and loose snow avalanches due to the new snow not bonding well to old snow surfaces. When the sun comes out today look for point releases on steep solar aspects. 

Storm snow easliy failing on buried surface hoar in a shovel tilt test yesterday.

Buried surface hoar over a micro sun crust @ 2200′ on Sunburst yesterday.

 

Avalanche Problem 2
  • 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

Weak snow (facets and depth hoar) in the lower layers of the snowpack lingers as an issue in our advisory area. It has been 8 days since the last human triggered avalanches on these layers. However, triggering a deep slab is still a possibility if you find the wrong spot and a concern due to the depth of slab overlying the weak snow. 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. Both near miss avalanche accidents last week were triggered in thinner areas of the snowpack, on slopes that already had tracks on them. The tricky part about this particular avalanche problem is that it is very difficult to assess. Obvious signs like whumpfing and shooting cracks are unlikely and stability tests may not be reactive. Just because a slope has tracks on it does not mean it is safe. Likely places to trigger a deep persistent slab will be near rocks or in thin zones where affecting the weak layer is more of a possibility. Likely triggers are large: snowmachines, groups of people or cornice falls. Identify and avoid terrain traps (like large gullies).

Snow pit @ 2200′ on Sunburst yesterday. Note the soft (weak, faceted snow) under the hard slab. 

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

Last weekend cornice cracks were reported along the back bowls of Seattle Ridge. 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. 

Weather
Sat, February 11th, 2017

Yesterday skies were obscured and light, low density snow fell throughout the day.  Temperatures were around 0 in the Alpine and teens/single digits in valley bottoms. Winds were mostly light and shifted from the West to the North. There was an uptick in winds that saw gusts up to 40 mph in the early evening. Light snow showers continued overnight.  

The chance for snow showers decreases this morning with clearing skies. Today temperatures will remain cold 3-13F and winds will be light and Northerly.  Tomorrow the pattern shifts as warm, moist air moves in with the first of a series of low pressure systems on track to affect the area. Stay tuned for details!  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 5   6    .3 58  
Summit Lake (1400′) 0    1  .1  25
Alyeska Mid (1700′)  6 6.5    .2  53

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 2    WNW-ENE 10 42  
Seattle Ridge (2400′)  -1 NNE    5 21  
Observations
Recent Observations for Turnagain Pass
Date Region Location
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
11/29/19 Turnagain Observation: Sunburst Ob #1
11/27/19 Turnagain Observation: Tincan
11/25/19 Turnagain Observation: Sunnyside
Riding Areas
Updated Mon, December 02nd, 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