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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 19th, 2024 - 7:00AM
Expires
Sat, January 20th, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′ today. Glide cracks continue to release across the forecast area, causing very large and destructive avalanches. Be aware of any glide cracks on the slope above you to identify areas where there is a risk of being caught in the runout of a glide avalanche. Lingering wind slabs about 1′ deep could exist in isolated areas at upper elevations, but with the outflow winds backing off yesterday these should be stubborn to trigger. Below 1000′ the avalanche danger is LOW.

Special Announcements

TONIGHT – Forecaster Chat at the Girdwood Brewing Co! Andrew Schauer will be discussing the different shades of MODERATE danger at the Girdwood Brewing Co. (6:30 to 8pm Jan 19). What does “spicy moderate” mean? More details HERE.

Fri, January 19th, 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
Sat, January 20th, 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
Sat, January 20th, 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
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

No new avalanches were reported yesterday that we know of.

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

Glide avalanches continue to release at an alarming rate across the forecast region and in neighboring areas like Summit Lake. If you have been following the forecast the past couple of weeks you have seen a lot of photos of massive glide avalanches releasing to the ground. The problem remains the same today, with the potential for glide cracks to release spontaneously and cause very large avalanches that involve the entire depth of the snowpack (5-7′ deep in many areas). Typically a glide avalanche is preceded by a glide crack, which means it is important to be vigilant and scan the slopes above you to check for the classic ‘brown frown’ which indicates that the entire snowpack is gliding along the ground surface. These commonly occur in areas with a smooth ground surface like tundra or bedrock, which we have plenty of in our forecast area. To mitigate this hazard it is important to minimize your time in the runout zone of potential glide avalanches.

Multiple generations of glide avalanches that have released along Penguin Ridge above the Seward Highway in Girdwood. Photo 1.18.24

This video from the Utah Avalanche Center illustrates the process of a glide avalanche. However, in our region the lubrication at the ground does not need to come from melting snow in the upper snowpack. We have enough moisture in the ground and at the base of the snowpack to cause glide avalanches even when temperatures are very cold and the sun is not yet strong enough to produce melt water to lubricate the ground surface. One theory is that the soil temperature and moisture content during the first snowfalls of the season can setup the conditions for the widespread glide cracks that we experience some years in the Turnagain Pass region.

Avalanche Problem 2
  • 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

At upper elevations it could still be possible to find a lingering wind slab to create an avalanche about 1′ deep. With the winds dying down on Wednesday these old wind slabs should be stubborn to trigger today, if it is still possible at all. Look for areas with hollow feeling snow on the surface or pillows of wind loaded snow to identify possible locations of wind slabs. Sometimes wind slabs on steep, convex slopes can remain human trigger-able for longer due to the unsupported nature of the terrain. Jumping on or riding across small, steep test slopes to look for shooting cracks or small avalanches is a great way to determine if wind slabs are still touchy in your location.

Plenty of wind affected snow at upper elevations, but we did not find any locations where wind slabs were reactive to the weight of a skier. Photo 1.18.24

Weather
Fri, January 19th, 2024

Yesterday:  Clear skies and light NE winds averaging 5-10 mph with gusts to 20 mph at upper elevations. Temperatures were in the single digits F at low elevations and low 20s F at upper elevations.

Today:  A high pressure ridge over the area will create continued clear skies and temperature inversions throughout the region. Temperatures at low elevations are expected to remain in the single digits F and in the teens to low 20s F at upper elevations. Winds should remain light out of the NE with averages of 5-10 mph.

Tomorrow:  Saturday looks like a carbon copy of Thursday and Friday, with the exception that temperatures are expected to get colder across the board. Inversions are still expected to be in place, but lower elevations could see temperatures in the negative single digits F with higher elevations dropping into the teens F. Winds should remain light. Sunday evening currently looks like the next chance for a refresh of snowfall.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 18 0 0 80
Summit Lake (1400′) 6 0 0 NA
Alyeska Mid (1700′) 19 0 0 78
Bear Valley – Portage (132′) 1 0 0
Grouse Ck – Seward (700′) 6 0 0 51

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23 NE 7 19
Seattle Ridge (2400′) 24 N 2 7
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.