Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, March 19th, 2022 - 7:00AM
Expires
Sun, March 20th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2500′. Consistent moderate winds over the past 24 hours have created fresh wind slabs along ridgelines and cross loaded gullies that are likely to be triggered by a person and possible for natural avalanches. These wind slabs may be sitting on top of a layer of buried surface hoar from 3.16.22 which could make them easier to trigger and have the potential to release on lower angle slopes. Consistent snowfall over the past 3 days has built up enough storm snow in some areas to cause storm slab avalanches in areas protected from the wind. In addition, a deeper layer of buried surface hoar from 3.2.22 could cause larger avalanches.

The avalanche danger is MODERATE from 1000′ to 2500′. Human triggered storm slabs sitting on top of the 3.16.22 buried surface hoar are possible for a person to trigger today especially where 6+” of new snow has fallen over the past 3 days. Below 1000′ the avalanche danger is LOW.

Special Announcements
  • Chugach State Park: A large remote triggered avalanche in the Eklutna/Twin Peaks area is a major warning sign of dangerous avalanche conditions in this part of Chugach State Park. The avalanche failed on a layer of basal facets and was remote triggered from 400′ below. See observations here for more details.
  • Join us TODAY Saturday, March 19th for the Turnagain Pass Avalanche Awareness Day in the Seattle Ridge parking lot. Chat with CNFAIC forecasters, try out some avalanche rescue gear, and demo a snowmachine or two from local businesses such as AMDS and Anchorage Yamaha and Polaris
Thanks to our sponsors!
Sat, March 19th, 2022
Alpine
Above 2,500'
Considerable (3)
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
Considerable (3)
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 a third hand report of a natural storm slab avalanche on W face of Eddies yesterday during the day. The depth was estimated at 10″ deep with the avalanche failing on the 3/16 buried surface hoar. The party that witnessed the natural avalanche also said they triggered a similar depth storm slab on their next lap in the same area. See ob here for more details.
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

A low intensity storm has been residing over our area for the past 3 days and dropped anywhere from 6-24+” of snow across the region. Coastal areas like Portage and Placer have been heavily favored by snowfall and likely received multiple feet of new snow in the past 3 days. Girdwood and Turnagain have been consistently picking up anywhere from 1-6″ of snow each day for the past 3 days, which is falling on top of the 3.16 buried surface hoar layer. Yesterday, a natural avalanche reported on W face of Eddies indicates that enough snow has fallen throughout the storm to cause storm snow avalanches in protected areas, which are likely easier to trigger due to the 3/16 buried surface hoar underneath.

As the snowfall tapers off today further natural avalanches will be unlikely in protected areas but human triggered storm slab avalanches are possible in areas that have received 6″ or more of new snow on top of the 3.16 buried surface hoar. Yesterday in the Crow Creek area we observed multiple melt freeze layers in the upper 6″ of the snowpack on southern aspects that are caused by the combination of warm temperatures and solar heating. These layers will add some strength to the upper snowpack and will make triggering a storm slab avalanche less likely on southern aspects.

In addition, fresh wind slabs 1-2′ deep will be likely to cause human triggered avalanches and possible for natural avalanches today, especially at upper elevations where the winds have been averaging 10-20 mph with gusts of 30-40 mph since yesterday around noon. We are somewhat blind to the upper elevation winds in Turnagain Pass because the Sunburst Weather stations stopped reporting data on 3.13, which we hope to get fixed next week. Look for hollow feeling snow, shooting cracks, and active wind loading to identify areas harboring wind slabs. The presence of the 3.16 buried surface hoar could make them easier to trigger on lower angle slopes. We recommend conservative decision-making and gradually easing into steeper terrain if you decide to travel in avalanche terrain today.

Loose Snow Avalanches: The storm over the past 3 days has provided a needed refresh to our snow surfaces. However, the added soft surface snow could lead to wet loose avalanche on southern aspects and dry loose avalanches on northern aspects.

Cornices: The combination of moist new snow and winds is a recipe for cornice building, which could make cornices more sensitive to failure under the weight of a person. As always, give a wide berth to cornices when walking along ridgelines and try to minimize time spent underneath them.

Glide Avalanches: The warm temperatures recently have opened up many glide cracks, especially along the E face of Seattle Ridge. These can release anytime and cause large avalanches, so it is best to minimize time spent underneath them.

Example of 3.16 buried surface hoar underneath the storm snow from the past 3 days, which was about 10-12″ deep on Eddies. Photo from Brooke Edwards 3.18.22

Melt freeze layers in the upper snowpack on a E aspect at 2700′. In areas with these melt freeze crusts we did not find either layer of BSH. Photo from Andy Moderow 3.18.22

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.

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

An older layer of buried surface hoar which was buried on 3.2 is a lingering concern for producing large avalanches with the potential for wide propagation and releasing on lower slope angles than typical. It has been a challenge to map the distribution of the 3.2 buried surface hoar layer because it is not always obvious in snowpits or hand pits. Prior observations have consistently shown the 3.2 BSH on Seattle Ridge and in some but not all areas on the skiers side of Turnagain Pass. The layer seems to be less widely distributed in the Girdwood area, but it is still worth looking for it before entering avalanche terrain. Instability tests like extended column tests and compression tests can help you locate the 3.2 BSH and assess how reactive it is in the area you are travelling.

Two layers of buried surface hoar from a snowpit on a N aspect on Eddies yesterday at around 2100′. Photo Brooke Edwards 3.18.22

Weather
Sat, March 19th, 2022

Yesterday: Broken to overcast skies and warm temperatures, reaching high 30s at lower elevations and mid to upper 20s at ridgetops. Over the past 24 hours Turnagain Pass and Portage received 6-8″ of new snow with Girdwood closer to 3-5″. Snow line rose up to 1200′ yesterday afternoon, with rain falling at the road elevation throughout Turnagain Pass. Wind speeds increased around noon yesterday and have been averaging 10-20 mph with gusts of 25-40 mph at ridgetops since then.

Today: Snowfall should taper off this morning with just a trace expected across region today. A low pressure system lingering in the gulf of Alaska could keep things cloudy and unsettled until it moves out or another low pressure moves in with more precipitation. Temperatures have fallen a bit overnight and should be in the low 30s at lower elevations today and low 20s at ridgetops. Winds look like they will remain consistent today with averages of 10-25 mph and gusts up to 30-40 mph at upper elevations.

Tomorrow: Looks similar to Saturday, but with winds dying down somewhat and the chance of improved visibility throughout the day. No significant new snow is expected on Sunday. Temperatures should remain relatively consistent over the next couple days. Monday looks like the best visibility day in the short term. More snowfall is expected to impact the area Tuesday afternoon through the rest of next week.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33 6 0.5 98
Summit Lake (1400′) 29 0 0 39
Alyeska Mid (1700′) 34 3 0.3 NA

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) NA NA NA NA
Seattle Ridge (2400′) 28 SE 6 22
Observations
Recent Observations for Turnagain Pass
Date Region Location
11/28/22 Turnagain Observation: Pastoral
11/27/22 Turnagain Avalanche: Tincan
11/26/22 Turnagain Observation: Eddies
11/26/22 Turnagain Observation: Eddies
11/26/22 Turnagain Observation: Lipps
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Sunnyside / Seattle Ridge
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Tincan Trees
11/25/22 Turnagain Observation: Tincan
Riding Areas
Updated Sun, November 27th, 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
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass
Closed
The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.

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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.