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Issued
Sun, January 24th, 2021 - 7:00AM
Expires
Mon, January 25th, 2021 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

Today’s avalanche danger will be CONSIDERABLE at elevations above 2500’, where it is likely a human could trigger an avalanche 1-2’ deep on wind-loaded terrain. Yesterday’s easterly ridgetop winds shifted overnight and are now blowing out of the northwest, which means fresh wind slabs may be found on multiple aspects today. There has been less wind-loading in the middle elevation band, but human-triggered avalanches will still be possible and the avalanche danger will be MODERATE from 1000’ to 2500’. With little to no new snow below 1000’, avalanches are unlikely and the avalanche danger is LOW.

Summit Lake: In addition to the concerns related fresh wind slabs, weak layers buried deeper in the relatively thin snowpack in the Summit Lake area mean deeper avalanches are possible.

Seward/Lost Lake/Snug: We have limited data on the snowpack in this area. If you get out in the Central Kenai mountains, or around Seward, please share your observations here.

Sun, January 24th, 2021
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

Tincan: Skiers reported sensitive storm slabs on short, steep terrain in the Tincan trees yesterday, which were very sensitive to ski cuts.

Skier-triggered storm slab release in the Tincan trees yesterday. That new snow is being drifted into sensitive wind slabs today. Photo: Matti Silta. 01.23.2021

Avalanche Problem 1
  • 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

After another round of strong winds and heavy snowfall yesterday, and continued winds through today, it is likely a person could trigger an avalanche 1-2’ deep on wind-loaded slopes. As visibility improves through the day, it will once again be possible to travel into higher elevations where it will be most likely to encounter fresh wind slabs. Luckily, there are some clues that can help you identify fresh wind loading:

  • Cracks shooting out from your snowmachine or skis, or the whumpf of the snowpack collapsing under your weight.
  • A ‘punchy’ feeling slab of stiff snow over weaker snow.
  • Smooth, rounded ‘pillows’ of dense snow.
  • Relatively firm snow at the surface.

Today it will be important to avoid steep slopes with any of these characteristics. Winds are expected to continue to be strong enough to blow snow around, and wind slabs will continue to be sensitive through the day. Yesterday’s strong easterly winds have shifted overnight and are now blowing out of the northwest, which means we will likely find fresh wind slabs on multiple aspects. Winds will not be as strong at mid- and low- elevations, making conditions less dangerous as you decrease in elevation.

Heavy snowfall and strong winds yesterday while we were riding and digging pits around Seattle Ridge. 01.23.2021

Cornices: The recent strong winds and wet snow have been ideal for building large cornices. We saw multiple natural cornice failures as the skies cleared following Monday’s storm, and we are expecting to see more of the same today. Cornices have a bad reputation for breaking much farther back than one would expect. If you find yourself traveling along ridgelines as skies begin to clear today, be sure to give them plenty of space. It will also be important to minimize the amount of time spent traveling under large cornices, as they can release naturally and unexpectedly.

Evidence of a large cornice fall above PMS bowl during the 1/18 storm. Similar activity is expected today. 01.19.2021.

In addition to these wind-related issues, we are also tracking a crust buried 1.5-2′ deep. We have gotten poor test results on weak snow associated with this crust on Cornbiscuit and just north of the Seattle Ridge uptrack. At this point, the layer is not giving us enough to concern to adjust our terrain use, but it is something we are paying attention to. If you get out and have any observations related to this layer, we’d love to hear about it.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
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.
More info at Avalanche.org

We are continuing to track the glide cracks opening up around the area. It is nearly impossible to predict when these cracks will release as large avalanches, so it is important to avoid spending near them or below them. So far, we have seen reports of recent glide activity at the following locations:

Girdwood Valley: Goat shoulder, Raggedtop lower SE shoulder, the far NE end of Penguin Ridge above Girdwood.

Turnagain Pass: The far northern end and SE aspect of Seattle Ridge, Warmup Bowl (-1 Bowl) NE aspect on the backside of Seattle Ridge.

Summit Lake: Gilpatrick’s S face, Devil’s Creek south side.

Weather
Sun, January 24th, 2021

Yesterday: A warm storm brought 1-1.5” water, with mostly rain below 1000’, and 6-10” snow at elevations above 1500’. Ridgetop winds were out of the east at 30-50 mph, and high temperatures were in the upper 20’s F at upper elevations and in the mid-30’s F at lower elevations.

Today: Winds have shifted and are now blowing out of the northwest, which will continue through the day, with ridgetop speeds expected to be around 20-25 mph. There is a chance of light snowfall this morning, but skies will clear up through the day, with partly sunny skies expected by this afternoon. Temperatures this morning are in the low 20’s to low 30’s F, and are expected to decline through the day and into tonight, reaching the high teens to high 20’s F overnight. We may see some lingering valley fog as skies clear and colder air moves in this afternoon.

Tomorrow: Skies will continue to clear up overnight, with mostly sunny skies on tap for tomorrow. Light easterly winds are expected to be around 5-10 mph, and high temperatures will be in the upper teens to low 20’s F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 9 0.6 135
Summit Lake (1400′) 32 0 0.1 45
Alyeska Mid (1700′) 31 5 1.05 116

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23 NE 23 72
Seattle Ridge (2400′) 27 SE* 14* 35*

*Seattle Ridge anemometer has been rimed over and not reporting since 5 p.m. yesterday.

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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