Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 28th, 2022 - 7:00AM
Expires
Sat, January 29th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000′ as winds continue to drift new snow into sensitive slabs 2′ deep or deeper. Human triggered avalanches will be likely with natural avalanches possible on wind-loaded slopes, becoming larger and more sensitive as snowfall continues and winds increase during the day.  Cautious route finding and conservative decision making is recommended.

The danger is MODERATE below 1000′, where it will be possible to trigger an avalanche about a foot deep in the storm snow that has fallen in the past two days.

 

PORTAGE/PLACER VALLEYS: Theses areas are expected to see at least double the snowfall of the rest of the core advisory area, making very dangerous avalanche conditions with natural avalanches likely and human-triggered avalanches very likely. Travel in avalanche terrain is not recommended in the Portage and Placer valleys.

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Fri, January 28th, 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

The steady flow of snowfall continues this morning, with another 6-9″ snow expected during the day today. Since the snow started accumulating early Thursday morning, storm totals are currently around 12-16″ in the mountains near Girdwood and 8-10″ at Turnagain Pass, with higher totals in the Portage and Placer valleys. The snow line has stayed below 500′ so far, but is expected to rise up to 1000′ by the end of the day today. Easterly winds have been blowing 10-20 mph near ridgetops with gusts at 30-40 mph, and are expected to bump up to 15-25 mph later today. As the snow continues to fall and winds increase slightly during the day, avalanches will become larger and easier to trigger. Conditions will be the most dangerous on wind loaded slopes, which will most likely be found near ridgelines, on convex rollovers, and in gullies. As snow stacks up during the day, be on the lookout for storm slab avalanches a foot deep or deeper on sheltered slopes as well. These wind slabs and storm slabs will usually give you warning signs of unstable conditions including shooting cracks, collapsing, and fresh avalanche activity, so pay attention as you travel in the mountains today.

In addition to the avalanche concerns related to the new snow, there is an outside chance that a person could trigger a larger avalanche on weak snow near the New Year’s crust, which is buried somewhere around 2-6′ deep. This is a tricky problem (which I attempt to explain in the video below, linked here), with high uncertainty and low likelihood. The only known recent activity on this weak layer was a large human-triggered avalanche on Tincan Proper last Thursday (details here). Continued stormy conditions will make travel in the alpine dangerous enough on their own today, but it will be important to keep this layer in mind as well, as one more reason to back off the bigger objectives. This will become more relevant as the storm breaks up over the weekend, but this issue will linger.

Loose Dry Avalanches (Sluffs): Yesterday we found it easy to trigger loose dry avalanches, which were running fast and picking up volume in the new snow. These will be getting larger and easier to trigger throughout the day, with natural avalanches likely as the snow continues. While it is unlikely a dry loose avalanche would bury a person, they can be big enough to carry an unwary traveler into terrain traps like trees, rocks, cliffs, or gullies.

Cornices: As snow continues to fall and winds continue to blow, cornices will grow and remain sensitive to human triggers. As always, give them plenty of room when you are traveling along ridgelines.

Dry loose debris on a small test slope at treeline on Tincan ridge yesterday. 01.27.2022

Weather
Fri, January 28th, 2022

Yesterday: Light snowfall brought 3-6″ to the mountains near Girdwood and only an inch at Turnagain Pass over the past 24 hours. Skies were mostly cloudy with some periods of sun poking through, with high temperatures in the mid 20’s to low 30’s F and lows in the mid 20’s F. Rain level stayed below 500′, with snow to sea level this morning. Winds were out of the east at 5-20 mph with gusts of 35-45 mph.

Today: Snow is expected to continue today, with another 6-9″ near Girdwood and Turnagain Pass, 14-20″ near Portage and Placer, and only 1-2″ at Summit Lake. Easterly winds are expected to pick up slightly throughout the day, blowing 15-25 mph with gusts of 30-40 mph by this afternoon. Rain level is expected to creep up to around 800-1000′ as temperatures hover in the upper 20’s to low 30’s F.

Tomorrow: Snowfall is expected to taper off by tomorrow morning, with another 2-4″ possible overnight tonight. Temperatures are expected to hang in the mid 20’s F overnight and slowly drop into the upper teens F during the day tomorrow. Winds are expected to back down to 5-10 mph out of the northwest, with clouds starting to break up as the low pressure center that has been bringing the snow exits to the east.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31 1 0.2 86
Summit Lake (1400′) 19 0 0.1 35
Alyeska Mid (1700′) 30 6 0.5 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 ENE 16 44
Seattle Ridge (2400′) 26 SE 8 19

 

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.