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Thu, January 28th, 2021 - 7:00AM
Fri, January 29th, 2021 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

Today the avalanche danger will be MODERATE at elevations above 1000’ in wind exposed terrain. As snow falls and winds increase, human triggered wind slabs will be possible near ridges, on wind-loaded slopes and in cross-loaded gullies. Pay attention to changing conditions and look for signs of instability. Give cornices a wide berth, avoid spending time under glide cracks and watch your sluff.

The avalanche danger is LOW below 1000’.

Special Announcements
  • Heading to Hatcher Pass? Be sure to check the Thursday Conditions Summary at hpavalanche.org.
  • Forecaster Chat #4: Snowmachine Specific- Head on a Swivel! Join us Tuesday, February 2nd from 7-8:30pm, for a VIRTUAL snowmachine-specific discussion with Graham Predeger and snowmachine educator and rider Tim Thomas from Haines. More info here. Stay tuned for a link to join the free virtual event.
Thu, January 28th, 2021
Above 2,500'
2 - Moderate
Avalanche risk
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.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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 a few very pleasant days of benign weather and easy travel, the next storm system is moving into the region. While lingering old winds slabs in steep terrain have been the primary concern, as winds increase and light snow falls, newly formed ones will become the problem today. There is settled soft snow available for wind transport as well and there is weak surface snow that the new snow will likely not bond to. Surface hoar and near surface facets have been observed from valley bottoms to ridgetops and in some locations rest on top of hard surfaces like wind crusts and melt-freeze crusts. This set-up has the potential to be very sensitive with a new wind slab on top.  It will be important to pay attention to changing conditions. Watch for blowing snow, look for signs of recent wind-loading and signs of instability like cracking from your skis, board or snowmachine. The storm is forecast to ramp up this evening into tomorrow. Expect the avalanche danger to increase overnight.

Loose snow avalanches (sluffs): Observers have been reporting sluffing as they have been accessing steeper terrain during these past few days. These sluffs have been increasing in size and moving faster as the surface snow has become more faceted and less cohesive. Light snow today will add more volume. If you are in steep wind protected terrain remember these can be dangerous if they take you off your feet or push you over a cliff, into trees or other terrain trap.

Cornices: If you are traveling along ridgelines, be sure to keep plenty of distance from the edge of the large cornices that have developed throughout the area. These things have a nasty tendency to break much further back than one would expect, and could fail under the weight of a snowmachine or a skier. ***There have been reports of cornice crevasses opening up. These are another hazard to watch out for as you travel near corniced ridges. 

Cornice crevasse opening along the Raggedtop ridgeline, 1.26.21.

Surface hoar and near surface facets over a melt-freeze crust, 1.27.21. Once buried this weak surface snow will likely become our new layer of concern. 


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

Glide cracks are appearing throughout the forecast area and there have been glide avalanches occurring in the past few days. With these becoming a hazard in terrain where people are skiing and snowmachining, remember it is important to limit time spent underneath glide cracks. Glide avalanches are totally unpredictable, not triggered by people and are the entire snowpack sliding at the ground. This type of avalanche could be large and unsurvivable if you happened to be in wrong place when one releases. If you see recent glide activity please let us know.

Thu, January 28th, 2021

Yesterday: Skies were mostly cloudy with temperatures in teens and low 20°Fs. Winds were light and easterly increasing in the late afternoon. Overnight skies were cloudy with light snow showers (to sea level) starting around midnight. Temperatures were in the teens to high 20°Fs, rising at lower elevations and falling at upper elevations. Winds were easterly 5-15 mph with gusts into the 20s.

Today: Skies will be cloudy with snow likely, 1-6″ to sea level. Temperatures will be in the 20°Fs and winds will be easterly 15-20 mph with gusts into the 30s and 40s. Overnight snow continues with an additional 5-10″ in the forecast. Temperatures remain in the 20°Fs and winds stay easterly 5-15 mph with gusts into the 30s and 40s.

Tomorrow: Snow continues but the track of the storm is still a bit uncertain making snow totals a bit of question mark. Winds will decrease and shift to the north and temperatures stay in the 20°Fs.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 19 0 0 125
Summit Lake (1400′) 12 0 0 44
Alyeska Mid (1700′) 20 1.5 0.08 109

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14 E 7 29
Seattle Ridge (2400′) 16 E 9 20
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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.