Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, December 10th, 2022 - 7:00AM
Expires
Sun, December 11th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′ today. Lingering wind slabs 1-2′ deep from yesterdays strong NW outflow winds are the main concern. It will be possible for a person to trigger a wind slab today and unlikely to see natural avalanches. Common areas to find wind slabs are near upper elevation ridgelines and gully features that have been wind loaded. Below 1000′ the avalanche danger is LOW. 

Special Announcements

Chugach State Park: The heavy snowfall this week in Anchorage has put a lot of stress on the thin and weak snowpack in the front range. We have several observations from across the front range of whumphing and shooting cracks, which are strong signs that the snowpack is unstable. We recommend being cautious with your terrain selection and paying careful attention to signs of instability if you are getting out in Chugach State Park this weekend.

Motorized Areas: All motorized areas remain closed. Stand by to see how the next storm system on Sunday/Monday plays out!

Forecaster Chat #1: Come join forecaster John Sykes at Alaska Mountaineering and Hiking from 7-8 pm on December 15th to discuss current conditions, how to submit quick and quality observations, and decision-making during complex snowpack conditions. Admission is free and all are welcome!

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Sat, December 10th, 2022
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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

Turnagain Pass: We saw a bunch of fresh wind slabs releasing naturally yesterday as the strong outflow winds gained enough strength to start reaching into the lower elevations in the Turnagain Pass area. Most of the activity we observed was along the South and East aspects of Seattle Ridge, but that is also where there was good light for viewing avalanches so there were likely many more hiding in the shadows. Here are a few examples, see this observation for more photos.

Natural wind slab on the E aspect of Seattle Ridge at about 2500′. Photo 12.9.22

Partially filled in wind slab along the E aspect of Seattle Ridge at 2600′. Photo 12.9.22

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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 several days of outflow winds, they finally built up enough wind speed to reach into the treeline elevations of Turnagain Pass yesterday. We observed several natural avalanches along Seattle ridge and saw active transport along all the ridgelines in the area. Surface conditions range from soft snow in protected areas to areas where the wind has blown off all the fresh snow down to a melt freeze crust.

The main concern for today will be lingering wind slabs 1-2′ deep from yesterdays wind event. These are most likely to be found on the leeward side of ridgelines and wind loaded gully features. The distribution of wind slabs in Turnagain Pass is more widespread than the past several outflow wind events because the winds affected lower elevation terrain yesterday.

To identify features that are potentially holding onto lingering wind slabs it is important to step out of the skin track and feel the surface snow conditions around you. Look for stiff and hollow feeling snow on the surface and areas where the winds have transported the snow into large drifts or pillows. Using small test slopes can be a good way to see how reactive wind slabs are before committing to more consequential terrain. These wind slabs were deposited on top of a layer of surface facets which could make them release on lower angle slopes and remain reactive for longer than normal.

Using a small test slope to check how reactive wind slabs were yesterday. This feature on Sunburst easily produced shooting cracks and small pockets of wind slab. Photo 12.9.22

Slippery skinning conditions along Sunburst ridge where the winds stripped off all the fresh snow down to a melt freeze crust. Photo 12.9.22

Weather
Sat, December 10th, 2022

Yesterday: Clear, cold, and windy. Winds were averaging around 10 mph out of the NW in Turnagain Pass with gusts to 20-30 mph. Much stronger winds were transporting snow along upper elevation ridgelines and in areas exposed to gap winds.

Today: We are transitioning from cold and clear with outflow winds to the onset of our next storm. Winds will switch to the South and decrease to 5-10 mph this morning. Temperatures will remain in the single digits to low teens. Cloud cover is expected to move into the area today, starting at higher elevations and gradually descending. Snowfall associated with our next system should start either late tonight or early Sunday morning.

Tomorrow: Heavy snowfall is expected on Sunday. Depending on the timing of the storm we could see anywhere from 6-12″ during the day on Sunday. From Sunday morning through Monday afternoon we are expecting 2-4′ of new snow, with higher totals in coastal areas. Temperatures will increase to the teens to low twenties on Sunday, and snowline is expected to remain at sea level. Winds are also expected to increase with the storm, with averages in the 30-40 mph range and gusts of 60+ mph.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 15 0 0 30
Summit Lake (1400′) 14 0 0 20
Alyeska Mid (1700′) 14 0 0 28
Bear Valley – Portage (132′) 21 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 6 WNW 10 34
Seattle Ridge (2400′) 13 NW 9 30
Observations
Recent Observations for Turnagain Pass
Date Region Location
02/08/23 Turnagain Observation: Eddie’s
02/07/23 Turnagain Observation: Seattle Ridge
02/07/23 Turnagain Avalanche: Pete’s North
02/06/23 Other Regions Observation: Johnson Pass to Bench Lake
02/05/23 Turnagain Observation: Rookie Hill
01/31/23 Turnagain Observation: Johnson Pass area
01/29/23 Turnagain Observation: Tincan Backdoor
01/28/23 Turnagain Observation: Sunburst
01/28/23 Turnagain Avalanche: Seattle Ridge
01/28/23 Turnagain Observation: Tincan Common
Riding Areas
Updated Fri, January 06th, 2023

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
Opened Dec 13th.
Placer River
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Skookum Drainage
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Turnagain Pass
Open
Opened Dec 13th.
Twentymile
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Seward District
Carter Lake
Open
Opened Dec 13th.
Lost Lake Trail
Open
Opened Dec 13th.
Primrose Trail
Open
Opened Dec 13th.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Open
Opened Dec 13th.
South Fork Snow River Corridor
Open
Opened Dec 13th.
Summit Lake
Open
Opened Dec 13th.

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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.