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Issued
Wed, January 10th, 2024 - 7:00AM
Expires
Thu, January 11th, 2024 - 7:00AM
Forecaster
Daniel Krueger
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000’. Triggering a large avalanche 2-4’ deep on a buried weak layer is the main concern. Where this problem exists is difficult to find in the field so we need to approach steep terrain cautiously. Wind slabs 1-2’ are also possible. Below 1000’ the danger is MODERATE where winds were not as strong. 

SEWARD/LOST LAKE: Strong northerly outflow winds will transport blowing snow in this region. Natural wind slab avalanches may occur throughout the day.

Wed, January 10th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Thu, January 11th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Thu, January 11th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Recent Avalanches

We saw multiple natural avalanches yesterday that had released during or right after Sunday’s storm. This includes activity on the north side of Tincan, Bertha creek near the Gold Pan area, front side of Seattle Ridge, and Zero Bowl on the back side of Seattle ridge. Most of these looked to be around 2 feet deep, and around 100-300 feet wide. Almost all of them released mid-slope in steep terrain. We also saw fresh glide activity on Penguin Ridge near Girdwood, on Summit Peak in the Summit Lake area, and just west of Devil’s Creek.

Recent large natural avalanche on the front side of Seattle Ridge, just a little south of the uptrack. 01.09.2024

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • 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

A layer of surface hoar 3-4’ deep has been preserved well enough to be the culprit of a large avalanche that remotely triggered on the backside of Seattle Ridge in Main Bowl on Monday. This has been the first known avalanche to be triggered remotely following Sunday’s storm, meaning you could trigger an avalanche on a steeper slope next to or above you even if you are on flatter terrain.

Our first big question is where was this layer preserved? It can be difficult to distinguish the spatial distribution of a buried surface hoar layer. In addition to Monday’s avalanche on the backside of Seattle Ridge, we noticed multiple natural avalanches that propagated wide and failed mid-slope, suggesting that a weak layer may have been the culprit for more than one avalanche. 

Until we allow more time to better understand how sensitive this layer is, sticking to smaller terrain away from convex features and steep lines to allow the snowpack to adjust is a great way to avoid getting caught in an avalanche. Keep in mind, these layers often do not give us clues such as shooting cracks or collapsing even when conditions may be dangerous.

Daniel standing next to the crown of an avalanche that was triggered remotely two days ago on a layer of buried surface hoar. 01.09.2024

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • 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

Wind slabs 1-2’ deep will be possible to be triggered by a human or snowmachine. Yesterday, we saw westerly winds blowing ample snow into fresh wind slabs and moderate overnight winds gusting 10-15 mph out of the west have continued to build fresh wind slabs. These can be found on leeward terrain features such as below ridgelines, rollover convexities, and in cross loaded gullies. 

Looking for red flags such as blowing snow, shooting cracks under you, as well as observing snow that becomes stiffer are good indicators you are traveling on a wind slab. Testing smaller slopes and pole probing for stiffer snow over softer snow are also good field tests. Be willing to change your plans if you find yourself on a reactive wind slab choosing less wind affected areas and softer snow. It is possible that a human caused wind slab avalanche could trigger a larger avalanche on the persistent layer. 

Wind-blown snow on Seattle Ridge depositing snow below the ridge. 01.09.2024

Avalanche Problem 3
  • Glide Avalanches
    Glide Avalanches
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

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

New glide cracks and glide avalanches have been seen from Summit all the way to Max’s outside of Girdwood after the storm. In many places they are above standard ski and snowmachine routes. Keep this in mind while you are picking your terrain and consider alternate routes if a skin track or uptrack you normally use traverses a slope with an open glide crack above. If you choose to travel under them only expose one person at a time and move quickly as these avalanches are unpredictable and very large.

New glide cracks forming above the Seattle Ridge uptrack. 01.09.24

Weather
Wed, January 10th, 2024

Yesterday: Clear skies for the first time after the storm. Ridgetop winds were moderate (10-15 mph) from the northwest with gusts near 20mph. We observed winds on Seattle Ridge that were higher than what the weather station recorded; our weather stations in this area do not always capture accurate wind speeds with northwest outflow events.  Temperatures steadily dropped from 20’s F to teens overnight.

Today: A few clouds in the morning with possible valley fog. Clouds will increase throughout the day as a front begins moving into the area overnight. Light winds (5-10 mph) from the west will switch out of the east. Temperatures will rise from single digits to teens by this afternoon.

Tomorrow: A front will move Thursday night bringing cloudy skies and moderate winds (10-20 mph) from the east with 30+ mph gusts. We may pick up a trace of new snow throughout the day. Temperatures will rise from teens to in the 20′ F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 11 0 0 92
Summit Lake (1400′) 7 0 0 68
Alyeska Mid (1700′) 16 0 0 86
Bear Valley – Portage (132′) 19 0 0
Grouse Ck – Seward (700′) 18 0 0 51

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 13 W 7 14
Seattle Ridge (2400′) 13 N 3 14
Observations
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02/20/24 Turnagain Observation: Seward Highway across from Johnson Pass TH
02/19/24 Turnagain Avalanche: Base of Seattle Ridge
02/18/24 Turnagain Observation: Lynx creek
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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.