Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, February 1st, 2022 - 7:00AM
Expires
Wed, February 2nd, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is rising to CONSIDERABLE today on all aspects above 1,000′ due to a weather system bringing strong easterly winds. Wind slabs are expected to form through the day and could release naturally. Slabs could build to 1-3 feet thick and should be easy for people to trigger. Watch for blowing snow and avoid being on or under any slope being wind loaded. Natural cornices breaks are also possible and could trigger an avalanche below.

The danger is MODERATE below 1,000′ due to the chance debris from avalanches releasing in higher terrain could run into this zone.

SUMMIT LAKE/LOST LAKE/SEWARD:  Strong ridgetop easterly winds will be impacting these areas as well and increased avalanche danger can be expected.

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Tue, February 1st, 2022
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)
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

After a brilliant sunny day yesterday, clouds are moving in with a chance for a few inches of snow and….I hate to say it….but strong easterly winds. By this afternoon forecasts are for 40-50mph with gusts in the 70’s. These winds should have a fairly easy time transporting much of that soft snow covering the slopes. Most of the impact should be above treeline, but also watch for exposed slopes in the trees that could see wind loading as well. With only 2-4″ of snow in the forecast, the winds will be the sole driver increasing the avalanche danger.

For anyone getting out today, paying close attention to what the winds are doing will be key. Watch for where they are blowing and how they are loading slopes. This easterly wind flow is great at loading many westerly aspects, but it also cross-loads the east face of Seattle Ridge (road side). So, all aspects are suspect. Feeling for stiffer snow over softer snow and cracking in the snow around you are also keys you’ve found a wind slab. If the visibility isn’t good enough to see, we should avoid being under or on steep slopes in case a natural avalanche occurs above us. Natural wind slabs are possible today and could be triggered by pieces or cornices breaking off. These new winds slabs could be anywhere from 1-3 feet thick depending on the strength of the winds and how much loose snow there is to blow on the surface. Many areas have over a foot of loose snow available for transport.

 

Wind slabs could step-down to the last storm snow interface around 2-3 deep and create a larger avalanche. This is the layer under the snow from the end of last week that is sitting on a thin freezing fog/drizzle crust. See the crown profile below from an avalanche last Saturday/Sunday on Seattle Ridge that failed just above this very thin crust.

Crown profile in a smaller avalanche triggered on either Saturday or Sunday in 2nd Bowl on the backside of Seattle Ridge. This thin crust is believed to also be the bed surface of the many avalanches that occurred on the back of Seattle Ridge on Saturday. 

In shallow areas of the forecast zone, such as south of Turnagain in the Silvertip area and outside the forecast zone in Summit Lake, wind slabs could break in deeper weak layers. These shallow zones have a much different snowpack than Turnagain. Take a look at this report from Summit Lake by two former CNFAIC forecasters, thanks ladies! With weaker layers near the surface, wind loading today may tip the balance, if not, something we are keeping an eye on for the future.

Weather
Tue, February 1st, 2022

Yesterday:  Sunny skies were over the region with some valley fog along Turnagain Arm. Ridgetop winds were light from the east until around 8pm when the starting climbing with the approaching weather system. Temperatures were in the teens.

Today:  Cloudy skies, light snow and strong easterly winds are forecast. Snow accumulations are 2-4″ for today with 1-3″ possible tonight, snow to sea level. Easterly winds are slated to blow 40-50mph along ridgelines with gusts near 70mph. Temperatures are in the teens in the high elevations and 20’sF near sea level.

Tomorrow:  This quick hitting storm moves out tomorrow morning. The weather models are showing partly cloudy skies (some valley fog) and no precipitation. Ridgetop winds look to be light and variable.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 18 0 0 91
Summit Lake (1400′) 8 0 0 33
Alyeska Mid (1700′) 17 0 0 87

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 18 NE
Seattle Ridge (2400′) 19 SE 25
Observations
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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.