Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, January 24th, 2023 - 7:00AM
Expires
Wed, January 25th, 2023 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The danger is HIGH above 2500′ as strong winds will make fresh wind slabs, pushing weak layers in the upper snowpack to their limit. Natural avalanches 2-4′ deep are likely and human triggered avalanches are very likely, which means travel in and below steep avalanche terrain is not recommended. The danger is CONSIDERABLE below 2500′. Winds will be a little lighter but the layer buried surface hoar makes human-triggered avalanches likely, and it is possible that avalanches staring in higher elevation start zones will run into lower elevation runout zones.

Special Announcements

Hatcher Pass will see a change in avalanche conditions and increased avalanche danger with the active weather over the past 24 hours. Be sure to check the forecast at hpavalanche.org if you are planning on heading that way.

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Tue, January 24th, 2023
Alpine
Above 2,500'
High (4)
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
High (4)
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

After 8 days in a row of human-triggered avalanches failing on a layer of buried surface hoar, we finally got one day with no reported avalanches.

Avalanche Problem 1
  • 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

The weather is picking up, and it is going to make avalanche conditions more dangerous today. Winds have been ramping up since just after sunset last night, and are expected to blow 25-35 mph with gusts of 30-45 through today into tonight. These winds will be building touchy wind slabs, which will be an ever bigger problem than normal because they are forming on top of a snowpack with a reactive weak layer buried 2′ deep on average.

We can expect to see some avalanche activity today as the winds continue to ramp up. While the most dangerous slopes will be those getting loaded today, it is important to remember that the layer of buried surface hoar we are dealing with is likely to produce avalanches in sheltered terrain as well. We’ve seen avalanches triggered remotely on this layer (detail from my field day at Tincan two days ago), which means you can trigger an avalanche from low-angle terrain below or adjacent to steeper slopes. As the layer gets buried deeper, it is becoming more difficult to assess with common travel tests like hand pits and test slopes. It is also giving fewer warning signs like shooting cracks or collapses before producing big avalanches. With how widespread the layer is, we don’t need to rely on these travel tests to know that we’re traveling on a dangerous setup. The best option for now is to assume you are traveling over a dangerous snowpack with a weak layer that is waiting for a trigger. The tricky snowpack actually makes travel advice kind of easy- put the big (or even medium) objectives on hold for now, stick to low-angle terrain, and avoid spending any time under steep slopes.

Cornice fall: Strong winds will continue to build large cornices today, and it is likely we will see some natural cornice failures. These cornices could likely trigger avalanches on steep slopes below. They may be hard to spot from a distance if visibility is limited today, but this is another reason to avoid spending time below steep slopes.

Could you find this layer in a hand pit? It’s 2 feet deep and becoming harder to detect, but still producing avalanches. We don’t want to try to outsmart this one. Photo from Tincan, 01.22.2023

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Aspect/Elevation
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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.

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

In addition to the problematic buried surface hoar layer mentioned above, we are still concerned with the possibility of triggering a massive avalanche on weak snow buried 4-8′ deep around the Thanksgiving crust. As time goes on it is becoming less likely to trigger something like this, but with another loading event underway, we still need to treat the layer with caution. Deep slab problems are possibly the most frustrating and challenging to deal with, since they can remain reactive to human triggers for weeks without giving any warning signs before big avalanches release. We don’t expect to see any red flags (shooting cracks, collapsing) and it is really hard to test even in a more thorough test pit, because stability tests are less reliable once a layer is buried deeper than about 3′ or so. For now, it is still possible to trigger an avalanche on this weak layer from a thin spot in the snowpack, and if an avalanche does release it is likely to propagate very long distances around multiple terrain features and aspects. This weak layer is just too big and too dangerous to mess with. Given the reactive layer mentioned in problem 1 above, this is just one more reason to stay on low angle terrain.

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Weather
Tue, January 24th, 2023

Yesterday: Things were fairly quiet weather-wise yesterday, with southeasterly winds blowing 5-10 mph for most of the way before ramping up to 15-20 mph just after sunset. Light precip brought 0.1-0.2″ water through the day, falling as rain below about 1100′ and 1-2″ snow at higher elevations. Temperatures were in the upper 20’s to mid 30’s F.

Today: Strong southeasterly winds are expected to persist through today into tonight with sustained speeds of 20-35 mph and gusts of 30-45  mph. We might see another inch or two of snow at higher elevations, with the rain line starting as high as 1800′ this morning, dropping to around 1000′ today, and creeping back up to 2000′ tonight. High temperatures should be in the upper 20’s F at higher elevations, reaching the mid to upper 30’s F at lower elevations.

Tomorrow: Precipitation intensity is expected to pick up a bit tonight as a small low pressure system moves into Prince William Sound. We may see 3-5″ snow at upper elevations in Girdwood and Turnagain Pass, with over a foot possible in Portage and Placer. Unfortunately the rain line is looking to sneak up, and we will likely see some rain as high as 2000′. Strong winds should continue through tonight, before backing down to 5-10 mph during the day tomorrow. Precipitation should wrap up for the most part by tomorrow morning, with some breaks in the clouds possible during the day.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33 0 0 69
Summit Lake (1400′) 31 0 0 34
Alyeska Mid (1700′) 32 2 0.2 71
Bear Valley – Portage (132′) 37 rain 0.3

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24 E 12 33
Seattle Ridge (2400′) 27 SE 9 20
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.