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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, January 7th, 2024 - 7:00AM
Expires
Mon, January 8th, 2024 - 7:00AM
Forecaster
Andrew Schauer
High Avalanche Danger
Travel in avalanche terrain is not recommended. Avoid being on or beneath all steep slopes.
Avalanche risk The Bottom Line

The avalanche danger will rise to HIGH at all elevations today as an intense storm impacts the area. 12-18″ new snow with winds gusting up to 100 mph will make large natural and human-triggered avalanches very likely. Big avalanches starting at upper elevations may run far down into valley bottoms. Travel in and below avalanche terrain is not recommended with these very dangerous avalanche conditions.

Special Announcements

There will be intermittent traffic delays Sunday January 7th, 2024 for Avalanche Hazard Reduction work from mileposts 37 to 46 on the Seward Highway, between the Sterling/ Seward Wye and Summit Lake. Motorists should expect delays of up to 45 minutes between 1:00 pm and 4:00pm. If you are planning on heading to Summit please avoid parking in the Summit Lake pullout, or touring on Summit Mtn. since they will be shooting these areas. Updates will be posted on the 511 system at  http://511.alaska.gov/.

The National Weather Service has issued a Winter Weather Advisory for the heavy snow and strong winds associated with this storm. Click here to read the whole advisory.

Sun, January 7th, 2024
Alpine
Above 2,500'
4 - High
Avalanche risk
Treeline
1,000'-2,500'
4 - High
Avalanche risk
Below Treeline
Below 1,000'
4 - High
Avalanche risk
Mon, January 8th, 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, January 8th, 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

People observed two recent wind slab avalanches in Turnagain Pass yesterday, which likely released sometime since Wednesday’s storm. The larger of the two was in the Widowmaker area in Main Bowl on the back side of Seattle Ridge, with debris burying a commonly used uptrack. The other was triggered by a cornice fall in PMS bowl on the southwest face of Magnum ridge. We are also seeing continued glide activity throughout the area.

Debris from a recent natural wind slab avalanche filling up a gulley commonly used as an uptrack on the back side of Seattle Ridge, with two active glide cracks in the background. Photo: Jake Ohms, 01.06.2024

Smaller wind slab triggered by a cornice falling onto the slope in PMS bowl on Magnum Ridge. Photo: Pat Gault/AAS 01.06.2024

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

We’re expecting to see an intense storm impact the area today, bringing 12-18″ snow to Girdwood and Turnagain Pass during the day, with 2-3′ likely in Portage and Placer. Snow has already started to trickle in, but the winds have arrived first and as of 5 am winds are already averaging 70 mph with gusts to 100 mph at the Sunburst weather station. The storm intensity is expected to peak right in the middle of the day today, with heavy snowfall and strong winds expected into tonight. All of this active weather will make large avalanches failing 1-3′ deep or deeper within new and windblown snow very likely today. With all of this  snow falling in just a few hours, it will be likely we will see large avalanches failing at upper elevations running into low-angle runout zones in valley bottoms. The layer of facets that got buried earlier in the week has the potential to make for even bigger avalanches failing a little deeper in the snowpack.

It is looking like another intense storm day today, and once again we’re avoiding spending any time in or below steep terrain. If you are planning on braving the winter driving conditions to go out and play around in the flats, be sure to stay well away from steep terrain as things become more exciting through the day.

Another intense storm has arrived, and we’re expecting snow totals to stack up today into tonight. Graphic courtesy of NWS Anchorage, 01.07.2024.

Avalanche Problem 2
  • 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

We’re continuing to see glide activity through the area, with fresh glide cracks and glide avalanches observed almost daily for the past two weeks. These avalanches are large and destructive, and although it’s impossible to predict exactly when a single slope will release, all of this recent activity indicates that we clearly have a glide avalanche problem. Luckily this problem is usually easy to manage and avoid if you limit your exposure to open glide cracks. With the high likelihood of big avalanches failing within the new snow today, this glide problem should be more of an afterthought for now since we’re already staying well away from steep terrain.

Large glide crack opening up on Magpie, in the Crow Creek drainage. 01.07.2024

Weather
Sun, January 7th, 2024

Yesterday: Skies were mostly cloudy yesterday with light easterly winds picking up in the afternoon through last night. Winds were around 5-15 mph for most of the day, but increased significantly and are currently averaging 70 mph with 100 mph gusts at ridgetops. High temperatures were in the mid 20’s to mid 30’s F with lows in the mid teens to low 20’s F. Precipitation started to trickle in yesterday afternoon and stations have picked up 0.5-0.8” SWE so far, equaling 2-8” snow at upper elevations with rain up to 800-1000’ and favoring Girdwood and Portage.

Today: Expect to see a full-blown storm day today. Winds are the first to arrive, currently blowing 70 mph with gusts to 100 mph at the Sunburst ridgetop weather station, and are expected to stay strong at 40-55 mph with gusts around 70 mph through the day. Precipitation intensity should pick up this morning, with 12-18” snow expected by this afternoon in Girdwood, Turnagain Pass, and Seward, 2-3’ possible in Portage and Placer, and 6-8” at Summit. The rain line is currently around 600-800’ but will start to drop as the storm picks up, making it down to around 100’ before the snow finishes tonight. High temperatures will be in the high 20’s to low 30’s F with overnight lows in the mid 20’s F.

Tomorrow: We should see another 4-8” snow tonight as the storm passes, with mild weather expected during the day tomorrow. Skies should be partly cloudy with light easterly winds at 5-10 mph. High temperatures will be in the 20’s F with lows in the mid teens to low 20’s F tomorrow night.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27 2 0.3 84
Summit Lake (1400′) 23 0 0 N/A
Alyeska Mid (1700′) 29 6 0.6 78
Bear Valley – Portage (132′) 35 rain 0.9
Grouse Ck – Seward (700′) 51 0 0.2 51

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21 ENE 27 102
Seattle Ridge (2400′) 24 SE 13 41
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
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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.