Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, February 11th, 2024 - 7:00AM
Expires
Mon, February 12th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000′. It is likely a person will be able to trigger a large avalanche on weak snow buried 2 to 3′ deep. It will also be easy to trigger avalanches near the surface where recent strong winds have blown the snow into sensitive slabs that will remain reactive today. Don’t let today’s quiet weather fool you- conditions remain dangerous and we’re sticking with low-angle terrain to avoid this problem for now. The danger will be MODERATE below 1000′ where the same problems may exist but will be harder to find.

Special Announcements

SnowBall 2024 is almost here! This Wednesday- Valentine’s Day, Feb 14 (7-11pm @ 49th St Brewing). The evening promises costumes, finger food, a rocking band, silent auction, and of course plenty of great company. Join us in supporting Chugach Avy as well as the Alaska Avalanche School. Details and tickets HERE.

Sun, February 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
Mon, February 12th, 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
Mon, February 12th, 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

A snowmachine triggered two avalanches in Main Bowl yesterday. Details are sparse, but the avalanches look to have failed on slopes that were loaded with snow and wind during the recent storm. Nobody was caught or buried in the avalanches.

Across the highway on Eddie’s Ridge, a skier triggered an avalanche about 80′ wide and 2.5-3′ deep, running about 120 vertical feet. As far as we know nobody was caught or carried in the avalanche.

Two Snowmachinie-triggered avalanches in Main Bowl yesterday (Feb. 10). Nobody was caught or buried. Photo shared by Joseph Fiskeaux on social media, 02.10.2024.

Skier-triggered avalanche on Eddie’s Ridge. Photo: Rafael Pease, 02.10.2024

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

The weak layer of snow that formed during January’s dry spell remains our main concern today. Friday’s storm brought 1.5 to 2.5″ snow water equivalent (SWE) to the area, which is adding a lot of stress to a layer that had already produced avalanches before it started snowing. We expect this layer to remain sensitive to human triggers today. It is now buried 2 to 3 feet deep on wind-sheltered slopes, and could be up to 3 to 5 feet deep or deeper on slopes that have been loaded by the strong winds we’ve seen over the past two days. Although the weather is supposed to be relatively quiet today, avalanche conditions remain dangerous.

These persistent weak layers are difficult to assess, and can give you misleading feedback prior to triggering a big avalanche. Some of the techniques we use to assess new snow problems (hand pits, slope tests, etc.) are usually not reliable for these persistent slab problems. Any signs like shooting cracks or collapsing are clear signs of dangerous conditions, but we might not always see these even when conditions are ripe for triggering an avalanche. Stability tests may be able to tell you a little bit more, but ultimately we already know there is a widespread weak layer that just got buried by a heavy storm, and we expect that setup to produce avalanches today. Rather than trying to assess our way into steeper terrain, we’re going to be giving this layer some time to heal and stick to lower-angle terrain for now.

This poor structure was already showing signs for concern prior to the storm that just added a whole lot of stress. There is now 1-2 feet of snow on top of the slab pictured above. 02.08.2024

 

 

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

Strong easterly winds throughout the most recent storm event have made another generation of wind slabs that we expect to remain reactive today. These will become larger and more likely to encounter as you gain elevation and get into the terrain that has been hit hardest by the wind. The most common features to find a reactive wind slab are steep slopes just below ridgelines, convex rolls, and steep gullies. These fresh wind slabs will feel stiffer on the surface, and you may notice a hollow, punchy feeling slab of snow if you hop off your snowmachine or step off the skin track and poke around. While wind slabs may sometimes be easier to manage than other avalanche problems, the deeper weak snow discussed in problem 1 above makes the wind slab problem a bit more severe today. A relatively small avalanche triggered near the surface has the potential to step down to that deeper weak layer, making a much bigger avalanche. This complicated combination of two different avalanche problems is a good reason to keep your terrain choices safe and simple for now.

Multiple natural wind slab avalanches in the alpine on Tincan Ridge seen yesterday. Photo: Tony Naciuk, 02.10.2024

Additional Concern
  • Glide Avalanches
    Glide Avalanches
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.
More info at Avalanche.org

It seems like the glide avalanche cycle that was producing large avalanches in December and January has slowed down for now. However, these avalanches are impossible to predict so we are not forgetting about the problem just yet. Avoid traveling under slopes with open glide cracks whenever possible, and be aware of the potential for falling into older glide cracks that are really difficult to identify now that they have been covered by the recent storms.

Weather
Sun, February 11th, 2024

Yesterday: Weather stations in Portage, Summit Pass, and Seward received another 0.3” water at road level yesterday, with rain to around 300 to 500’ and 4 to 8” snow at upper elevations. Girdwood and Turnagain Pass received a trace of new snow. Skies were partly to mostly cloudy with high temperatures in the mid 20s to low 30s F. Winds were averaging 15 to 25 mph out of the east with gusts of 35 to 50 mph for most of the day, but have calmed down overnight and are currently blowing at 5 to 10 mph.

Today: We should see a spell of quiet weather between storm systems today, with partly cloudy skies and scattered snow showers bringing a trace of snow to sea level. Winds should stay light out of the east for the first part of the day, increasing in the afternoon to 20 to 25 mph with gusts to 30 mph. High temperatures are expected to be in the mid to upper 20s F with lows in the high teens to low 20s F.

Tomorrow: Active weather returns tomorrow, with strong easterly winds picking up ahead of the next round of snow. Expect to see ridgetop winds of 30 to 50 mph with gusts of 40 to 60 mph and mostly cloudy skies. Most areas should see  1 to 3” snow during the day, with the exception of areas closer to the coast which may see closer to 5 to 7”. The rain line is expected to rise overnight as precipitation continues, making it up to 1200 to 1400 feet overnight. High temperatures will be in the mid 20s to low 30s F with overnight temperatures staying in the upper 20s to  low 30s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28 tr 0.1 86
Summit Lake (1400′) 28 3 0.2 45
Alyeska Mid (1700′) 30 1 0.07 93
Bear Valley – Portage (132′) 36 0 0.3
Grouse Ck (700′) 32 3 0.3 63

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 ENE 13 43
Seattle Ridge (2400′) 24 SE* 9* 15*

*Seattle Ridge anemometer rimed and not reporting data since 5 p.m. yesterday.

Observations
Recent Observations for Turnagain Pass
Date Region Location
02/24/24 Turnagain Observation: TinCan Backdoor/ Center Ridge
02/22/24 Turnagain Avalanche: Lynx Creek
02/22/24 Turnagain Observation: Turnagain, Seattle, Mt Ascension
02/21/24 Turnagain Observation: Tincan Trees
02/21/24 Turnagain Observation: Sunburst
02/20/24 Turnagain Avalanche: Tincan
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
02/18/24 Turnagain Observation: Tincan Trees
Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.


Subscribe to Turnagain Pass
Avalanche Forecast by Email

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.