Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 9th, 2021 - 7:00AM
Expires
Sun, January 10th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE on all slopes above 500′. Dangerous avalanche conditions exist. Large wind slab avalanches in the Alpine and storm slab avalanches in the trees, 3-4+’ thick, are likely for a person or snowmachine to trigger. These could be triggered remotely from the bottom, side or top. The 2.5-3.5 feet of new snow from the past three days has yet to bond. Cautious route-finding and conservative decision-making are essential. Look for signs of instability and choose terrain wisely.

LOST LAKE and mountains near Seward: Heavy snowfall has been reported in these areas. Where 2-3 feet of new snow has fallen, large and dangerous human triggered avalanches are likely.

Summer Hiking Trails: Avalanche danger exists on summer trails that pass through avalanche paths, such as they Byron Glacier Trail and many others.

*A Special Weather Statement has been issued by the National Weather Service. Today marks the beginning of a strong storm system moving in, peaking tomorrow and Monday. Avalanche danger is expected to rise to HIGH tomorrow if this storm verifies.

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Sat, January 9th, 2021
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
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
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

The remnants of widespread avalanche activity were seen yesterday morning. Despite the low visibility, the bottom of many avalanche paths that can be seen from the Seward Highway from Bird to Seward had large debris piles. Additionally, many steep rolling hills along the highway had avalanched up to 3′ deep (storm snow avalanches). There were three reports of avalanche activity in specific areas from yesterday:

Johnson Pass:  Several slab avalanches (2.5-4′ thick) were remotely triggered by snowmachiners on/near the Johnson Pass winter trail on steep rolls and hills. This group made it to an elevation of 2,200′ before turning around due to numerous Red Flags. In one case, they tested a very low consequence steep roll connected to a larger roll (40-60′ tall and ~40 degrees steep) and the entire face in every direction released. The larger avalanche paths in the area had avalanched and large debris piles were seen. On their way out they noticed many other steep rolls that they had triggered on the way in from flatter terrain.

Sunburst:  A large, 3′ thick, storm slab that released naturally earlier Friday morning was seen near the Sunburst up-track in the trees (photo below). Report HERE.

Wolverine:  A large natural slab avalanche was seen on the lower SW shoulder of Wolverine ridge on the northern end of Turnagain Pass. Slab was around 3-4′ thick and around 300′ wide. Likely released early Friday morning.

Storm slab avalanche in the ‘trees’ on Sunburst, in the mid-elevation. 1.8.21. Photo: Anonymous. 

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

It is not the day to push into steep terrain, nor will it be through the weekend as the danger rises again. Not only are avalanches likely to be triggered, they could be triggered remotely as was seen along the Johnson Pass trail. The mountains just had 2.5 -3.5′ of snow over the past three days along with strong east winds. Another 3′ or more is expected starting later today through Monday. It’s clear from what is listed above in our ‘recent avalanches’ section that we just went through a natural avalanche cycle and the snow isn’t bonding quickly. It fell on a weak surface (that surface we were skiing, boarding or riding on over the New Year), which is composed of small near surface facets (sugary snow) with buried surface hoar. Both these layers once buried can cause us grief as it limits new snow from bonding right away. How long will it take for the snow to bond this time, well that’s yet to be determined. With more weather on the way, it’s a moot point really as today we are still well within the 48-hour rule of letting the mountains adjust before getting onto the slopes that are luring us.

Storm slabs, these are defined as slabs composed of the new snow that have little wind effect, are equal in depth to the new snow, which is in the 2.5-3′ range. Storm slabs are what is present mostly in the trees and the type of avalanche most likely to catch a person today. Even on small steep rollovers an avalanche could pose a significant threat if you’re caught upside down and pinned in a terrain trap. For tree skiing or riding, make sure to keep an eye on your partners, be suspect of steep rollovers, and watch for cracking in the snow around you.

Although only 2-5″ of new snow is expected today, it will be the sustained moderate to strong ridgetop winds adding to the thickness of the wind slabs. Wind slabs could now be as thick as 5-6′, maybe even thicker.

Cornices: This storm was your classic Chugach sticky snow kind of event with just the right amount of wind to build large cornices. With more wind ramping up today ahead of this next Chugach storm, they may continue to release naturally and possibly trigger an avalanche below. Although these are hard to reach safely now, once these storm are over, they could be quite dangerous and easy to break.

Snow pit at 1,400′ on Seattle Ridge to the looker’s right of Repeat Offender slide path. 1.8.21.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

4-7′ below the snow surface is the Dec. 1 rain crust/facet combination that exists at elevations between 1,000′ and 2,500′. This layer continues to degrade and weaken; turning into a faceted layer in places. Although it is unlikely that a person could trigger an avalanche on it, we are watching to see if a storm slab avalanche is able to step down and make it fail. So far we have no information on this, but it is a question that will help us assess if the layer is an issue moving forward or not.

Weather
Sat, January 9th, 2021

Yesterday: Light snowfall and obscured skies were over the Turnagain Pass area yesterday. Between 4-6″ of snow fell (~0.5″ of SWE) with lesser amounts in Girdwood and south of Turnagain Pass. The rain/snow line hovered near 200-300′. Ridgetop winds have been averaging 20-30mph from the east with gusts up to 57mph. Temperatures were in mid 30’sF at sea level, near 32F at 1,000′ and in the mid 20’sF along ridgelines.

Today: Obscured skies and light snow showers are expected to continue through today before increasing in intensity tonight. Between 2-5″ should fall today with another 6-10″ overnight tonight. Rain/snow line looks to drop to close to sea level before rising to 300-400′ tonight. Ridgetop easterly winds will remain in the 25-30mph range and are expected to increase tonight. Temperatures had dropped a few degrees this morning and should remain in the low to mid 30’sF at sea level and near 20F along ridgelines.

Tomorrow: The low-pressure front pushing in today will ramp up tomorrow and through Monday (possibly longer..!). Heavy snowfall is slated for Sunday and Monday totaling a potential 3+ more feet of snow in the mountains. Temperatures remain on the warmish side and the rain/snow line could creep as high as 1,000′. Stay tuned!

Fun Fact: As of yesterday, Turnagain Pass has had more snowfall (225″) than the Pass had all of last season (220″)! Wow…

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30 4 0.5 100
Summit Lake (1400′) 29 0 0 36
Alyeska Mid (1700′) 30 4 0.4 98

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 NE 24 57
Seattle Ridge (2400′) 24 *N/A *N/A *N/A

*Settle Ridge anemometer is rimed over and not reporting.

Observations
Recent Observations for Turnagain Pass
Date Region Location
04/09/21 Turnagain Observation: Girdwood to Turnagain Road Observations
04/05/21 Turnagain Avalanche: Resort bowl Seattle creek head wall
04/04/21 Turnagain Observation: Center Ridge
04/03/21 Turnagain Observation: Repeat Offender – Seattle Ridge
04/02/21 Turnagain Observation: Seattle Ridge
04/01/21 Turnagain Observation: Pete’s
03/31/21 Turnagain Observation: Tincan
03/30/21 Turnagain Observation: Eddies
03/30/21 Turnagain Observation: Sunburst North
03/28/21 Turnagain Observation: Sunburst
Riding Areas
Updated Thu, April 01st, 2021

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
Open
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Summit Lake
Open

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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.