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Issued
Fri, January 12th, 2024 - 7:00AM
Expires
Sat, January 13th, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000′ today. Fresh wind slabs 1-2′ deep forming from strong easterly winds will be widespread in exposed areas and are very likely to release naturally or by human triggering. A weak layer of buried surface hoar 2-4′ deep is also still a concern and could cause large avalanches on specific slopes. Finally, glide avalanches continue to release naturally across the forecast area, causing very large avalanches. Below 1000′ the avalanche danger is MODERATE.

Seward/Lost Lake: Coastal areas near Seward could see 5-7″ of new snow today combined with strong winds. This will cause increasing avalanche danger throughout the day today, especially in exposed areas near treeline and above.

Special Announcements

Girdwood Forecaster Chat – Friday, Jan 19th! Mark your calendars for Andrew Schauer’s discussion on the different shades of MODERATE danger at the Girdwood Brewing Co. (6:30pm Jan 19). More details HERE.

Fri, January 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
Sat, January 13th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Sat, January 13th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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

Glide avalanches continue to release across the forecast area, with a large avalanche occurring yesterday on Sunburst and another that was witnessed on Seattle Ridge. Other than these glides there were no new avalanches reported yesterday.

Large glide avalanche that released just below the common uptrack on Sunburst. Photo from Rapheal Pease 1.11.24

Avalanche Problem 1
  • 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

Winds have been howling for the past 24 hours, and are expected to continue throughout the day today. Average wind speeds on Sunburst were 25-35 mph out of the east last night with gusts up to 80 mph. With plenty of soft snow on the surface and 2-6″ of new snowfall overnight, these winds will be forming wind slabs roughly 1-2′ deep along upper elevation ridgelines and exposed terrain features near treeline. This type of avalanche tends to be much more reactive immediately after it forms, and since the winds are expected to continue throughout the day today you may find wind slabs more reactive than normal. Keep an eye out for active wind loading, shooting cracks on the snow surface, and hollow feeling snow to identify areas that could be harboring wind slabs.

In coastal areas like Portage and Placer Valley there could be up to a foot of new snow by the end of the day today. Avalanches in sheltered areas are also possible if this much snow accumulates today. Using small test slopes or hand pits can be a good way to determine how well the new snow is bonding to the old snow surface before entering consequential terrain.

Sustained strong winds over the past 24 hours will cause a lot of snow transport at upper elevations and build fresh wind slabs. 1.12.24

Avalanche Problem 2
  • 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

Our search for buried surface hoar throughout the forecast area continues, and so far we have not found the layer to be very widespread. There was a notable human triggered avalanche on Monday in Main Bowl on Seattle Ridge that we confirmed released on a layer of buried surface hoar that formed during the cold spell in late December. However, in many other locations we have been unable to find the surface hoar in the snowpack and the weak layer looks more like a soft layer of facets buried 2-4′ deep. It is still possible that there are locations where there is buried surface hoar preserved in the snowpack, which could still cause large human triggered avalanches. To avoid this avalanche problem you simply need to stick to low angle terrain. Unfortunately it is impossible to know exactly where this layer could still be an issue, so there is a lot of uncertainty involved in managing this risk.

Weak layer of facets buried about 2′ deep in Girdwood valley, but not showing obvious signs of being reactive. Photo 1.11.24

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

Glide avalanches continue to plague the forecast area, with new releases occurring in very well traveled locations in Girdwood and on both the skiers side and motorized side of Turnagain Pass. Most recently there was a very large avalanche just below the common uptrack on Sunburst that likely occurred on Wednesday or Thursday. There is no way to predict where the next glide avalanche will release, so it is critical to be aware of any glide cracks above you and try to minimize your time underneath. This problem is a particular concern on the Seattle Ridge uptrack where the entire Repeat Offender slide path is covered with glide cracks.

Large glide release on Sunburst. Photo shared via Instagram

Weather
Fri, January 12th, 2024

Yesterday:  Mostly cloudy skies to start the day, with cloud cover increasing in the afternoon and becoming obscured. Winds were strong throughout the day with averages of 15-25 mph and gusts to 50 mph out of the east at upper elevations during the day. Overnight winds increased to averages of 25-35 mph and gusts up to 80 mph out of the east. Light snowfall started in the afternoon and continued through the night, with 2-6″ of new snow falling across the region. Girdwood and Portage/Placer were favored and Turnagain looks to have only picked up a few inches. Temperatures were in the low 30s at sea level and low 20s to high teens at upper elevations.

Today:  Strong winds and light snowfall is expected to continue today, with an additional 2-4″ of accumulation expected in Girdwood and Turnagain pass and up to 10-12″ in Portage and Placer. Winds will start out averaging 25-35 mph out of the east with gusts of 50+ mph. Throughout the day winds will gradually decrease, dropping to averages of 10-20 mph out of the southeast by this evening. Mostly cloudy skies are expected to persist throughout the day, with more clouds expected in coastal areas near Portage and Placer. Temperatures should remain in the low 30s F near sea level and low 20s to high teens F at upper elevations. Rain line is expected to remain at sea level today.

Tomorrow: Saturday looks like a mirror image of today. With winds gradually increasing throughout the day and light snowfall expected to increase towards to afternoon. Snow accumulation is expected to only be 1-3″ on Saturday, with Portage and Placer receiving 3-6″. Temperatures will remain in the low 30s near sea level and low 20s at upper elevations for most of the day Saturday, but will increase slightly Saturday evening which will bring rain line up to 400-500′.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28 1 0.1 87
Summit Lake (1400′) 27 0 0 N/A
Alyeska Mid (1700′) 27 7 0.6 85
Bear Valley – Portage (132′) 34 3 0.7
Grouse Ck – Seward (700′) 31 2 0.2 51

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 18 ENE 26 80
Seattle Ridge (2400′) 22 SE 17 31
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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.