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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, January 13th, 2024 - 7:00AM
Expires
Sun, January 14th, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger will rise to CONSIDERABLE above 2500′ today, as winds pick up in the afternoon forming fresh wind slabs roughly 1′ deep. Natural and human triggered wind slabs will become more likely as the winds increase throughout the day. Glide avalanches are a major concern right now due to the potential for creating very large avalanches 4-6′ deep and their unpredictable nature. Glide cracks have been observed across the forecast area and we recommend giving them a wide berth and trying to avoid travelling underneath them. Avalanches on a buried weak layer 2-4′ deep are also a concern in isolated areas where the weak layers remain intact. Below 2500′ the avalanche danger is MODERATE.

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.

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
Sun, January 14th, 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
Sun, January 14th, 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

No recent avalanches were reported yesterday. Glide avalanches on Sunburst, Penguin Ridge, and Seattle Ridge from Wednesday and Thursday are the most recent known avalanches.

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 across the forecast area, causing very large and destructive avalanches 4-6′ deep on commonly traveled routes. While it is normal for us to have occasional glide avalanches throughout the winter during most seasons, the past few weeks have been unique because of the frequency of glide avalanches and how widespread glide cracks are. A few notable events include a glide release on the Repeat Offender slide path which threatens the motorized uptrack on Seattle Ridge, one just below the normal skin track on Sunburst, and an older release on the SW face of Cornbiscuit. Just because these areas have already had glide avalanches does not mean that they are safe now. Many areas still have widespread glide cracks above popular routes, which can spontaneously release at any time.

The best way to manage this unique avalanche hazard is to avoid spending time underneath glide cracks. This is easier said than done on days like today where poor visibility can obscure your ability to see the slopes above you. If you find yourself needing to travel under a glide crack, try to minimize your time on that slope and spread out your group so you are not all exposed at the same time. The randomness and huge destructive potential of glide avalanches make them a scary hazard.

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

Strong winds Friday morning likely formed wind slabs 1-2′ deep along upper elevation ridgelines that could still be possible for a person to trigger. Today the winds will start off light but are expected to increase throughout the day and return to averages of 20-30 mph and gusts to 50 mph out of the E by this afternoon. This fresh round of winds will build another generation of wind slabs roughly 1′ deep at upper elevations. To avoid accidentally triggering a wind slab keep an eye out for active wind transport along ridgelines, shooting cracks, and hollow or drum like snow. Jumping on small, steep slopes can be a good way to determine how reactive wind slabs are.

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

It’s been almost a week since the last big storm triggered a cycle of large avalanches that we believe failed on a weak layer of facets and surface hoar that was buried on January 2nd. The only human triggered avalanche we know of on this layer was in Main Bowl on Seattle ridge and was remotely triggered by a group of snowmachiners riding along the adjacent ridge. Observations from across the region this week have hinted that the distribution of the Jan. 2 buried surface hoar is spotty. On isolated slopes where the buried surface hoar remains intact it could still be possible to trigger an avalanche 2-4′ deep. This is most likely in sheltered bowls and areas that have not seen much traffic in recent days like Lynx Creek, Silvertip, or Johnson Pass. Due to the depth of the weak layer it is difficult to assess without stopping to dig a snowpit. Stability tests like a compression test (CT) or extended column test (ECT) can be useful to determine if there is a concerning buried weak layer in the area you are travelling, especially if you get propagation across your column in an ECT.

Forecaster Daniel Krueger conducting a crown profile on the avalanche that was remotely triggered in Main Bowl on January 8th, 2024. Photo 1.9.24

Weather
Sat, January 13th, 2024

Yesterday:  Mostly cloudy skies with light to moderate snowfall but minimal snow accumulation (1-3″). Temperatures were in the low 30s to mid 20s F at lower elevations and in the upper teens F at upper elevations. Winds were strongest Friday morning with averages of 15-25 mph and gusts to 50 mph out of the ENE. In the afternoon and overnight the winds died down to averages of 5-15 mph with gusts to 25 mph out of the ENE.

Today:  Another storm front will move through the forecast area this afternoon. Winds will start out light this morning with averages of 10-20 mph out of the SE and increase throughout the day. By this evening winds are expected to average 20-30 mph with gusts to 50 mph out of the E. Light snowfall will accompany this storm front and is expected to start around 2 pm. Snow accumulation is expected to be minimal in Turnagain Pass and Girdwood with roughly 1″ falling on Saturday, but totals could be higher closer to Portage and Placer. Rain line will creep up to 500′ overnight on Saturday.

Tomorrow: Unsettled weather is expected to continue throughout Sunday, with light snowfall but limited snow accumulation. Rain line should drop back down to sea level Sunday morning, as temperatures decrease throughout the day. Winds should shift the the south and decrease to averages of 5-15 mph in the first half of the day on Sunday before shifting to the SW and remaining light in the afternoon. Cloud cover is expected to decrease Sunday afternoon with periods of broken skies and improved visibility.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 24 0 0.0 86
Summit Lake (1400′) 25 0 0.0 36
Alyeska Mid (1700′) 26 2 0.15 86
Bear Valley – Portage (132′) 32 3 0.34
Grouse Ck – Seward (700′) 30 1 0.1 50

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17 ENE 14 55
Seattle Ridge (2400′) 20 SE 7 21
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.