Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, February 8th, 2023 - 7:00AM
Expires
Thu, February 9th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE on all aspects above 1,000′. Triggering a lingering wind slab or storm slab composed of the new snow from Sunday/Monday may still be possible. These slabs would be in the 1-2′ deep range. Cornices are also a concern along ridgelines. Give these an extra wide berth. Additionally, there could still be a chance a larger avalanche releases in an old layer of buried surface hoar 2-4′ deep. The danger is LOW below 1,000′.

SUMMIT LAKE:  Snowfall has been trickling into the Summit Lake area. Be aware that larger avalanches could be triggered due to buried weak layers.

SEWARD/LOST LAKE:  Around a foot of snow has fallen in Seward over the past 24-hours. This has increased avalanche danger for the mountains around Seward and extra caution is advised.

Special Announcements

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Wed, February 8th, 2023
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

There were no known avalanches triggered yesterday. The last known avalanches were two days ago during and right after Sunday/Monday’s storm (10-18″ of storm total). These were small human triggered avalanches in the new storm snow and some larger natural avalanches in the higher terrain. Photo below of one these larger natural slides on Seattle Ridge.

 

Natural wind slab avalanche on the front side (SE face) of Seattle Ridge. Avalanche looked to have released on Monday, 2.6.23, at the tail end of the storm. Photo taken 2.7.23.

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

Cloudy skies, a few snow flurries, and light variable winds are on tap for today. This should not be enough weather to impact avalanche conditions. Hence, the main avalanche concerns will be how the storm snow from Sunday and Monday is bonding to the old surfaces. Anywhere from 10-18″ of snow fell during that storm. I was out on Seattle Ridge yesterday hunting for areas the snow had not bonded well. I had no luck. This is great news for improving stability, but also only one data point. Things to watch for today:

  • Wind slabs in the higher elevations. Strong winds during the storm clearly built wind slabs and whether these are still touchy or not is the question. Watch for cracking in the snow and feel for stiffer snow over softer snow. Wind slabs could be quite stubborn, which can allow us onto them before releasing.
  • Storm slabs on steep slopes sheltered from the winds. Keep an eye out for any signs the new snow isn’t bonding. Quick hand pits, jumping on small test rolls/slopes, and watching for any signs the snow is cracking around you are good ways to assess this.
  • Cornices are big. As always give these guys a wide berth.

Even though things are looking better for stability, remember to always follow safe travel protocol. This is exposing one person at a time, having escape routes planned, and being sure our partners are watching us and know how to use their rescue gear in the event an avalanche releases. Also, don’t forget there is a layer of old buried surface hoar under our feet – mentioned below in Problem 2.

 

One of many quick hand pits on the backside of Seattle yesterday. This one is in Main Bowl around 2,200′. No weakness was found between the storm snow and the old surface. 2.7.23.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • 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.

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

Buried 2-4′ deep now is that Jan 10th buried surface hoar that created a rash of human triggered avalanches over two weeks ago. This layer has been showing signs of healing in general, but not completely. John had concerning snowpit results on Pete’s North on Monday. If you missed it – check out his video HERE.

This layer likely became more reactive with the new load of snow. With quiet weather ahead, the layer should become less reactive again. How likely it is we could trigger it is the big question. It could be fairly unlikely at this point, but there is still a lot of uncertainty. For now, don’t forget that layer is there and that it could create a very large avalanche, especially in steep and consequential terrain.

Additional Concern
  • Deep Persistent Slabs
    Deep Persistent Slabs
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.
More info at Avalanche.org

We are still tracking the Thanksgiving facet/crust combo at the base of the snowpack. In the Turnagain Pass area where the snowpack is thick we believe this layer to be un-reactive and now in a dormant phase. However, in shallower snowpack zones, such as Silvertip and south of the Pass proper, there is still some uncertainty. If the layer is still an issue, it would be in these shallow zones. Other questionable layers may also exist in shallow areas. It’s good to keep this in mind if headed to areas where the pack is less than 6′ feet deep or so. A surprise, or outlier avalanche, may not be out of the question.

Weather
Wed, February 8th, 2023

Yesterday:  Mostly cloudy skies were over the region with a few break allowing sun to shine through. The only precipitation were a few flurries at low elevations along Turnagain Arm. Ridgetop winds were 5-10mph from the east. Temperatures were in the upper 20’sF at the lower elevations and near 20F along ridgelines.

Today:  Cloudy skies and light snow showers are forecast in most areas. Between 1-3″ of accumulation is expected through the day and into tonight. Ridgetop winds should be light and variable before turning northerly (staying light, ~5mph) later today. Temperatures are on a cooling trend and should be in the teens along ridgelines and 20’s at lower elevations.

Tomorrow:  A ridge of high pressure builds that will bring cooler temperatures and clearing skies. Some valley fog may be seen. No precipitation is expected and ridgetop winds will stay north to northwesterly in the 5-10mph range. Some clouds may start pushing in on Friday ahead of the next storm system that could move in for the weekend. Stay tuned.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 24 0 0 70
Summit Lake (1400′) 21 0 0 37
Alyeska Mid (1700′) 24 trace 0.02 70
Bear Valley – Portage (132′) 29 1 0.1

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17 NE 7 18
Seattle Ridge (2400′) 20 SE 5 11
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.