Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, February 14th, 2022 - 7:00AM
Expires
Tue, February 15th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 2500′ today. Lingering wind slabs up to 1′ deep are possible for a person to trigger, especially in steeper terrain along ridgelines. Another storm is approaching the area this afternoon which will bring increased winds and cloud cover and 4-8″ of snowfall by tomorrow morning. The new snow and winds will create fresh wind slabs that will be more reactive to human triggers and will increase the avalanche danger. Below 2500′ the avalanche danger is LOW.

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Mon, February 14th, 2022
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
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
Low (1)
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
  • 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

The next storm system is approaching our area today and should arrive in the late afternoon or early evening, bringing increasing cloud cover, winds, and snowfall. This will build fresh wind slabs up to 1′ deep and make human triggered avalanches more likely. Until then the mountains have been fairly quiet over the past couple days, with light to moderate winds and broken cloud cover. A few avalanches have been observed in the forecast area but they have been isolated to areas with suspected lingering weak layers of decomposing new snow underneath wind slabs and areas with higher than average winds, like along Turnagain Arm. It will still be possible to trigger a lingering wind slab up to 1′ deep in these areas, especially in steeper terrain, and we recommend evaluating wind loaded features before entering avalanche terrain.

Loose Avalanches: Dry loose avalanches (sluffs) were observed in steeper terrain yesterday and are expected again today. The soft snow on the surface is only a few inches deep in most areas so these sluffs are fairly low volume. In addition, the snow surface on S face of Cornbiscuit was getting heated up by the sun yesterday and causing roller balls to run from the ridgetop all the way to the valley floor.

Snowfall totals for Monday night into Tuesday morning storm system. Hatcher Pass is the big winner with 12-18″, Girdwood gets a silver with 6-8″, and Turnagain and Summit tie for bronze with 4-6″. Graphic courtesy of NWS Anchorage 2.13.22

Wind effect along Cornbiscuit ridgeline. The sun was strong enough to create a moist snow surface and send rollerballs all the way down to the valley bottom on S face of Cornbiscuit. Photo 2.13.22

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

An old weak layer of buried facets from November is still lurking in the snowpack and has shown signs of reactivating in Summit Lake where there is a shallow overall snowpack depth (details here). Summit Lake is outside our forecast area, but some of the southern portions of the forecast area are in a transitional zone between the deeper snowpack of Turnagain Pass and the shallower snowpack of Summit Lake. Similarly, the Crow Pass area is on the far northern end of our forecast area and is a transitional zone between the deeper snowpack of Girdwood and the shallower snowpack of the Chugach Front Range. We have also found similar shallow and weak snowpack structure in wind scoured areas of Turnagain Pass, although the distribution of the shallow snowpack is less widespread (example here). In these shallow snowpack areas the November facets are only buried a few feet deep and remain weak and have shown potential to propagate in snow pit tests. Triggering an avalanche on this layer remains unlikely within our forecast area, however the potential for this layer to create large avalanches has us keeping close track of its distribution and watching for any new avalanches that are able to release or step down onto these old facets.

Snowpack in a wind scoured area on N side of Magnum that has weak structure due to buried November facets below the New Years Crust. Photo Andy Moderow 2.13.22

Weather
Mon, February 14th, 2022

Yesterday: Calm winds, variable cloud cover, and an occasional snow, rain, or hail shower with no meaningful accumulation. In Turnagain Pass the visibility was pretty good in the alpine with occasional periods of flat light. When the sun poked through the clouds it felt warm and was affecting snow surface conditions on steep south facing terrain.

Today: Today will start out similar to yesterday with calm winds and low cloud cover until the next storm front arrives in the afternoon, bringing snowfall and increased S and SE winds. Temperatures should be in the 20s today but snow line could rise up to 1000′ early Tuesday morning during the end of the precipitation. Snowfall totals will be 1-3″ this evening and 3-6″ overnight tonight. Higher snowfall amounts are expected for Hatcher Pass.

Tomorrow: Snowfall should taper off by the morning tomorrow with the potential for improved visibility during the day. Storm totals are expected to be 6-8″ in Girdwood and 4-6″ for Turnagain Pass and Summit Lake. Winds will increase to 5-25 mph out of the W on Tuesday and temperatures will be in the 30s at lower elevations and 20s at upper elevations.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27 0 0 90
Summit Lake (1400′) 20 0 0 38
Alyeska Mid (1700′) 28 tr 0.04 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 var* 5 21
Seattle Ridge (2400′) 22 var* 3 10

*variable wind direction, E in the morning, then W in the afternoon, then N in the evening and overnight.

Observations
Recent Observations for Turnagain Pass
Date Region Location
05/17/22 Turnagain Avalanche: Sunburst
05/17/22 Turnagain Observation: Tincan Ridge
05/11/22 Turnagain Avalanche: Cornbiscuit and Magnum west faces
05/07/22 Turnagain Observation: Granddaddy
04/29/22 Turnagain Observation: Sunburst wx station
04/28/22 Turnagain Observation: More Turnagain Pass/Summit Lake wet slab activity
04/27/22 Turnagain Observation: Magnum
04/27/22 Turnagain Observation: Girdwood/Summit/Turnagain Road obs
04/24/22 Turnagain Avalanche: Seattle Ridge – large glide avalanche on Repeat Offender path
04/24/22 Turnagain Avalanche: Seattle Ridge uptrack
Riding Areas
Updated Fri, May 13th, 2022

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 as of May 1 per Forest Plan.
Placer River
Closed
Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage
Closed
Closed as of April 1st per Forest Plan.
Turnagain Pass
Open
Open. Extended opening through May 31.
Twentymile
Closed
Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake
Closed
Closed as of May 1 per Forest Plan.
Lost Lake Trail
Closed
Closed as of May 1 per Forest Plan.
Primrose Trail
Closed
Closed as of May 1 per Forest Plan.
Resurrection Pass Trail
Closed
Closed as of May 1 per Forest Plan.
Snug Harbor
Closed
Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor
Closed
Closed as of May 1 per Forest Plan.
Summit Lake
Closed
Closed as of May 1 per Forest Plan.

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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.