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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, March 13th, 2024 - 7:00AM
Expires
Thu, March 14th, 2024 - 7:00AM
Forecaster
Daniel Krueger
Avalanche risk The Bottom Line

The avalanche danger remains HIGH in the alpine today. Human triggered avalanches are very likely as over 2.5′ of new snow has fallen in the past 2 days accompanied by strong winds. Fresh wind slabs 1 to 3′ deep will be easy to trigger and may release naturally. Additionally, both storm and wind slabs are sitting on top of weak layers buried 2.5′ to 4′ deep that may make it easier to trigger a large avalanche.

The avalanche danger is CONSIDERABLE below 2,500′ in areas less affected by the winds. We recommend avoiding avalanche terrain that is being actively wind loaded and taking a cautious approach at all elevations. To avoid these problems, stick to lower angle slopes and avoid runout zones where a larger avalanche can run further.

Roof avalanches: With 2′ to 3′ of new snow and warming temperatures through the day be on the lookout for roof avalanches. Look up when passing through doorways and keep an eye on kids and pets.

Seward and Summit: Seward received over 11″ and Summit received a few inches of new snow yesterday accompanied by east winds gusting 20 to 40mph. Both areas will have fresh wind slabs and storm snow that will be sensitive to human triggers. In Summit, new snow and wind slabs 1′ deep will be on top of buried weak layers that are still concerning and capable of releasing a large avalanche 1.5′ to 3′ deep. To avoid these problems, stick to slopes less than 30 degrees.

Special Announcements

Turnagain Pass Avalanche Awareness Day – Saturday, March 23
Swing by the Turnagain motorized parking lot between noon and 4pm to grab a hotdog, practice your beacons skills (we’ll have a small park set up), chat with the forecast team, and possibly test out a demo snowmachine provided by local dealers. This is a fun day designed to connect with our excellent backcountry community!

Wed, March 13th, 2024
Alpine
Above 2,500'
4 - High
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
Thu, March 14th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
Thu, March 14th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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

An avalanche likely triggered remotely in the Placer valley yesterday. It is possible this avalanche failed on a buried weak layer at low to mid elevations. Otherwise, with low clouds and poor visibility we were not able to see recent avalanche activity. It is likely natural avalanches have released from this storm.

Human triggered avalanche that may have been remotely triggered at low to mid elevations in the Placer valley. Photo by Chris Yelverton 3.12.2024

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

This storm delivered nearly 2.5′ of new snow (2.5″ SWE) over the past 2 days in Turnagain with more in Placer valley, accompanied with overnight winds from the northeast gusting 50+ mph overnight. This will make it likely for a human to trigger an avalanche 2 to 3′ deep. With the rain line rising to 500′ this problem can be found at all elevations and slopes. Fresh wind slabs 1 to 3′ deep will be easy to trigger on wind loaded slopes and could release naturally. Red flags such as recent avalanches, blowing snow, firm snow over soft snow, cracking, and collapsing on small test slopes are all great indicators the snowpack is still being stressed and capable of avalanching. It is not recommended to travel on steep wind loaded slopes. If you decide to travel in avalanche terrain assess the snowpack cautiously and have a conservative mindset as you travel today. If you want to avoid these problems choose lower angle slopes and avoid runouts as larger avalanches can run further.

Loose Avalanches: It is likely to trigger a dry loose avalanche on steep northerly slopes. As the sun tries to show itself through the clouds today, wet loose avalanches may become a concern on steep southerly slopes, especially near trees and rocks. If the sunlight penetrates through the clouds, it has the potential to trap heat which can warm the snow faster than you would expect. Look for roller balls as indicators that the surface is capable of releasing a wet loose avalanche.

Cornices: Cornices likely grew immensely larger from strong winds and snow available to transport. Additionally, the snowpack warmed up yesterday and is expected to warm up today which will make easier for a cornice to release above you which can trigger a large avalanche.

John leading the hip deep skin track through 2.5′ of new snow on Tincan. Photo 3.12.2024

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 is possible to trigger an avalanche 3 to 4ft deep on several weak layers that are being stressed by over 2.5ft of new snow. Our main concern is a weak layer of facets buried on March 5th at lower to mid elevations on all slopes. There are also reports of buried surface hoar at all elevations. We are uncertain how widespread and sensitive this layer is to being triggered. Yesterday, a natural avalanche was reported in the trees in Placer valley which is believed to have been remotely triggered. This is bullseye information telling us that a persistent problem is still an issue as remotely triggered avalanches can be triggered as you approach a slope and can release above or adjacent to you. Red flags such as cracking, collapsing, and whumphfing sounds are all indicators that the slope is capable of avalanching, however, there may be no evidence until an avalanche occurs.

Weather
Wed, March 13th, 2024

Yesterday: Low clouds and snowy conditions all day added another 8″ of new snow in the Turnagain area. Mid elevation winds were light, however Sunburst recorded sustained winds gusting 50+ mph from the northeast! Temperatures rose throughout the day with from mid 20 F to 33 F with a rain line around 600′ reported in the Girdwood valley.

Today: A few inches of light snow flurries are forecast to continue throughout the day with sunshine trying to poke through the clouds. East winds averaging 10 to 20 mph with 30 to 40 mph gusts. Temperatures look to be in the mid to high 20’s F.

Tomorrow: Partly cloudy skies accompanied with west winds averaging 5 to 10 mph with 20 mph ridgetop gusts. No new snow is expected as the looks to dissipate over the Kenai Peninsula.  Slightly cooler temperatures (15 to 25 F) are expected tomorrow.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28 8 1 115
Summit Lake (1400′) 30 2 0.1 48
Alyeska Mid (1700′) 30 4 0.36 110
Bear Valley – Portage (132′) 33 0.6
Grouse Ck (700′) 26 11 2 77

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 ENE 32 47
Seattle Ridge (2400′) 24 SE 12 19
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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.