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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, January 15th, 2024 - 7:00AM
Expires
Tue, January 16th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

Avalanche danger remains MODERATE above 1000′ today. As the active glide avalanche cycle continues, our main concern is the alarming rate of glide avalanches in busy areas. You can manage this problem by spending as little time as possible under glide cracks. Consider using alternate routes whenever possible if your normal route travels under an open glide crack. In addition to the glide problem, northwesterly winds will begin to pick up for some parts of the advisory area and will increase the chances of a person triggering an avalanche up to a foot deep where the snow has been blown into a sensitive slab.

The danger is LOW below 1000′. The main concern is the small chance of a large glide avalanche failing at a higher elevation running into a low-elevation runout zone.

 

LOST LAKE/SEWARD: Outflow winds are expected to hit these southern zones today, ahead of the rest of the forecast area. Conditions will become more reactive as the winds pick up starting today.

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.

Mon, January 15th, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Tue, January 16th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Tue, January 16th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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

The ongoing glide cycle continues, with a large glide avalanche on the Repeat Offender avalanche path on Seattle Ridge yesterday morning. The avalanche was on the looker’s left side of the motorized uptrack and ran down to the flats.

New glide avalanche on the Repeat Offender slide path above the Seattle Ridge uptrack. This happened sometime between sunset Saturday and 8:30 Sunday morning. 01.14.2024

Avalanche Problem 1
  • 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

The unusually active glide cycle continues, with another large glide avalanche yesterday on the front side of Seattle Ridge right next to the motorized uptrack. This is just the latest in a cycle that has lasted for weeks, with glide cracks opening up and releasing in busy areas. While these avalanches are notoriously hard to predict, all of the recent activity is making it clear that we can expect to see more glide avalanches for now.

These big avalanches are nothing to mess with. They fail right at the ground and involve the entire season’s snowpack, now around 5-7 feet deep. The clear weather that is expected to arrive today should make it easier to identify open glide cracks as you travel. These will look like a gaping brown crack where the snow has started to peel down the mountain, or they may be a more subtle, wrinkled or cracked texture where a crack is just starting to open up. Either type of glide crack can release spontaneously. We need to stay extra cautious traveling around these monsters. Consider using an alternate route whenever possible if your normal route would take you directly under an open glide crack. For some areas like the Seattle Ridge uptrack, there may not be a reasonable alternate route. In those cases, you can still minimize your exposure by traveling one at a time, moving as quickly as possible, and being certain that you are watching your partners from areas that are not exposed to overhead hazard.

Cropped view of the Repeat Offender glide. The trees on the slope give a better idea of the size of this avalanche. 01.14.2024

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • 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.
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

A high pressure system moves into the area today, bringing with it sunny skies and northwesterly winds. Winds should remain light enough that they won’t be moving very much snow in most of the advisory area, but some parts may see the winds start to pick up today. Keep a look out for a new round of wind slabs forming today in the zones that tend to get hit hardest by outflow winds like Seward, Lost Lake, Portage, and along the Turnagain Arm. It is looking like this will be more of a concern starting later in the day tomorrow, but it will be good to keep on your radar today.

 

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

We’re still monitoring the weaker snow that was buried at the beginning of January and was partly responsible for the reactive storm slab avalanche cycle we saw last weekend. The only known human-triggered avalanche on this weak layer was a week ago, when a snowmachiner triggered a large avalanche on the back side of Seattle Ridge remotely from a flat ridgeline that failed on a layer of buried surface hoar. We’ve been targeting this layer in snowpits since then and have not seen concerning results. However, surface hoar problems can be spotty so we are still keeping this in mind. This is especially true for zones that we are still lacking data like Johnson Pass, Lynx Creek, or Silvertip Creek to name a few.

Weather
Mon, January 15th, 2024

Yesterday: Skies were cloudy with spotty snow showers that brought intermittent snow but no accumulation to the forecast area. At lower elevations there were some periods of a light, misty drizzle. Winds were light out of the east in the morning, switching westerly through the day with average speeds around 5-10 mph and gusts of 10-20 mph. High temperatures were in the mid 20s to low 30s F, dropping to the teens to low 20s F this morning with temperatures in the single digits in Summit.

Today: High pressure moves in today, with mostly sunny skies and some lingering valley clouds likely. Winds have switched to the northwest but should stay light for most of the forecast area today with average speeds of 5-15 mph and gusts of 10-25 mph. Expect to see stronger winds at the usual gaps today like Portage and Seward. Temperatures will get up into the upper teens to low 20s F during the day and should stay there tonight.

Tomorrow: Northwest outflow winds are expected to ramp up through the day tomorrow, with average speeds of 15-30 mph by the end of the day. Skies should remain mostly sunny with high temperatures in the low to mid 20s F and overnight lows in the mid teens F. No precipitation is expected.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 24 0 0 84
Summit Lake (1400′) 20 0 0 35
Alyeska Mid (1700′) 25 tr tr 83
Bear Valley – Portage (132′) 30 0 0 –
Grouse Ck – Seward (700′) 27 0 0 51

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16 W 4 21
Seattle Ridge (2400′) 20 SSE 1 8

 

Observations
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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.
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