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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 2nd, 2024 - 7:00AM
Expires
Wed, January 3rd, 2024 - 7:00AM
Forecaster
Mik Dalpes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1,000’. Strong easterly winds will make natural and human triggered wind slab avalanches 1-2’ deep likely. The glide avalanche cycle continues to be a concern, these avalanches can be very large and release without warning. With low visibility expected today we recommend avoiding the areas where glide avalanches and cracks have been observed. Below 1,000’ the danger is MODERATE.

Tue, January 2nd, 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
Wed, January 3rd, 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
Wed, January 3rd, 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
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

A few small wind slabs were triggered yesterday on Tincan, you can find the report here. The glide avalanche cycle continues in the Turnagain and Summit zones with at least two new glide avalanches noticed yesterday. One of these slides is directly across from Magnum on the motorized side and one on Gilpatrick mountain.

Fresh glide avalanche noticed yesterday January 1 located directly across from Magnum on the motorized side. photo 1.1.24

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

2024 is bringing us a New Year’s storm right off the bat. Ridgetop winds started picking up yesterday morning as a storm system approaches from the Aleutian chain. The wind will be the primary driver increasing the avalanche danger today, with easterly winds averaging 20-30 mph and gusts of 40-50 mph combined with 3-6” of new snow. Expect to find fresh wind slabs 1-2’ deep along ridgelines, rollovers, and across gully features. These avalanches will become larger and more reactive throughout the day as the snow and wind increase. 

Weak surface snow has been observed since the last storm so these fresh wind slabs could be forming on some weaker layers that may make them more reactive than normal. They may break wider or on a lower angle than you may expect. Wind deposited snow may feel hollow or firmer beneath your feet or machine and may produce cracks that shoot out from you. Jumping on a test slope or digging a hand pit are good ways to assess today’s conditions. Expect storm day riding conditions today with better visibility and softer snow in the trees. 

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

The glide avalanche cycle continues to be a concern today as fresh glide avalanches and cracks were noticed yesterday on the west side of Turnagain Pass and in the Summit zone.  New avalanches and cracks have been noticed almost on a daily basis for the last two weeks and with low visibility today it will be a good plan to stay away from any of those known locations. This includes the majority of the east facing slopes on Seattle Ridge and the south face of Cornbiscuit on the non-motorized side. 

New glide avalanche seen yesterday on Gilpatrick Mountain in the Summit zone.  Photo credit Trevor Clayton, 1.1.24

Weather
Tue, January 2nd, 2024

Yesterday: Mostly cloudy skies and relatively warm temperatures in the low 20s to low 30s F. Winds averaged 10-20 mph at upper elevations with gusts of 20-35 mph. Intermittent rain and snow showers, especially near coastal areas, but no significant accumulation.

Today: Strong winds picked up overnight, with averages of 20-30 mph and gusts up to 50 mph. Those winds should be sustained throughout the day today, with snowfall starting between 9am and 12pm. We are expecting 3-6″ of new snow for Girdwood and Turnagain Pass, with higher totals of 8-12″ possible for upper elevations near Portage and Placer. Rain line will rise throughout the day, starting close to sea level and increasing to 1000-1200′ by this evening.

Tomorrow: The bulk of the snowfall from the current storm system is expected to arrive overnight Tuesday and continue throughout the day on Wednesday. Current estimates show an additional 10-14″ of snow falling in Girdwood and Turnagain Pass, with up to 20-25″ of new snow in Portage and Placer. Rain line is expected to remain roughly 900-1100′ throughout the storm. Winds will further increase on Tuesday night and Wednesday, with averages of 40-60 mph and gusts of 75+ mph.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 1 0.1 75
Summit Lake (1400′) 27 0 0.0 N/A
Alyeska Mid (1700′) 29 trace 0.01 69
Bear Valley – Portage (132′) 36 0 0.06
Grouse Ck – Seward (700′) 32 0 0.0 47

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 ENE 19 52
Seattle Ridge (2400′) 25 SE 8 15
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.