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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, January 25th, 2023 - 7:00AM
Expires
Thu, January 26th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1,000′ on all aspects. Triggering a slab avalanche around 2′ remains likely. These slabs are failing on buried surface hoar and can be triggered remotely (from the side, top, or bottom) of a slope. Additionally, other avalanche problems such as cornice falls and wind slabs could be found at the high elevations, which could also trigger a larger avalanche below. The danger is MODERATE below 1,000′ in large avalanche paths, where an avalanche releasing above could send debris.

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Wed, January 25th, 2023
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

We did not see or hear of any avalanche activity yesterday, however, it seems to have been a very quiet day in the backcountry in general.

The last known avalanche was three days ago. A slab was triggered by Andrew and avy center intern Megan Guinn, just below them when they were digging snow pits on a lower southerly aspect on Tincan. More details HERE.

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

Although the region did get a bit of weather over the past 24 hours, the main avalanche concern remains triggering a 2′ slab on buried surface hoar. There have been many of these easily triggered for 10 days now, some catching and carrying people last weekend. Slabs have been releasing in open areas in the trees and in the higher elevations. These are being triggered by people on slopes and remotely, next to slopes. It’s starting to get a little trickier because the weak layer is generally buried too deep to rely on hand pits and quick tests we can do easily, without digging in the snow. We are getting to the point where we simply have to remember the problem is there. Even test slopes may not give us great information. That said, sticking to our motto this year, a cautious mindset, conservative terrain choices, and really being aware of our exposure to slopes that have to potential to slide is key.

Early this morning 1-4″ of new snow fell above 1,500′ (rain below…) and winds have been strong enough to move snow around at the higher elevations for 24 hours now. Due to this, we can expect that wind slabs have formed and cornices have grown. These issues are overlying the buried surface hoar problem. If folks venture to the ridgelines today, be mindful of fresh wind slabs and know cornices could be triggered easily and break further back than expected. Any smaller avalanche or cornice fall could trigger a larger avalanche.

As we roll into late January, with 1 hour and 44 minutes more daylight :), the sun is going to become a factor quick when skies decide to clear. This could happen this afternoon, or more likely over the next several days. In this case, we should start seeing avalanches on southerly aspects. Warming by the sun can trigger small loose snow avalanches, but it can also cause larger slabs to release or make them easier for us to trigger. Something to keep in mind moving forward.

 

Photo of the slab triggered on a southerly aspect of Tincan (2,000′) on Sunday, 1.22.23, by Andrew and Megan. 

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

It’s getting to be old news, but we are still concerned about an avalanche breaking in buried weak layers at the base of the snowpack, this could create a huge slide. The weak layers are facets surrounding the Thanksgiving crust, buried anywhere from 4-8′ deep now and a foot or two above the ground. Continued small amounts of snowfall, strong winds, and warm temperatures are slowly adding stress to the snowpack.

These kinds of avalanches release during weather events, rapid warming (could we see this on Saturday?), or a person hitting a thin spot in the slab. It’s impossible to say how close certain slopes are to catastrophic failure or not. So in the meantime, our guard remains up.  There is enough to worry about in the top 3 feet of the snowpack, this just puts the icing on the cake this year to keep things more mellow that we may want to.

Weather
Wed, January 25th, 2023

Yesterday:  Mostly cloudy skies were over the region yesterday. Ridgetop winds were easterly, moderate to strong (15-25mph, gusts up to 50). Light rain fell overnight close to 1,500′ with wet snow flurries above, total accumulation around 1-2″ above 2,500′. Temperatures were warm, in the mid 30’sF at 1,500′ and mid 20’sF along the higher ridgelines.

Today:  The weather system over the area should push out this morning and skies could break up with some sun poking through later today. A few flurries (light rain below 1,500′) may be seen before noon, but no real accumulation is expected. Ridgetop winds look to remain easterly, but decrease to 5-15mph with gusts near 15-25. Temperatures should remain warm, low 30’s in the mid elevations and mid 20’sF along the ridgelines.

Tomorrow:  A break in weather is forecast for several days starting tomorrow. Models are showing patchy cloud cover with a chance for clearing skies, light westerly winds, and slightly cooling temperatures for Thursday. Beginning Friday, we could start seeing warming in the higher elevations coupled with mostly clear skies. Stay tuned as Saturday looks like it could be ‘really’ warm, like 40F in high elevations, we’ll see.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 34 1 0.1 68
Summit Lake (1400′) 33 0 0 34
Alyeska Mid (1700′) 32 1 0.2 71
Bear Valley – Portage (132′) 37 rain 1

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25 ENE 17 49
Seattle Ridge (2400′) 27 SE 15 24

 

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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.