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Mon, March 29th, 2021 - 7:00AM
Tue, March 30th, 2021 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations today. Triggering a slab avalanche 1-3′ deep is possible on slopes 35° degrees and steeper. Terrain that has been recently wind-loaded is the most suspect. Keep in mind that there are buried weak layers in the snowpack. Pay attention to changing conditions as the edge of a storm system impacts the forecast area today and tonight. Assess the snowpack as you travel, identify areas of concern and evaluate terrain consequences.

Special Announcements
  • It was a very hard weekend for the Alaskan snow community.  We are heartbroken to report that a woman from Fairbanks lost her life after being caught in an avalanche while skiing near the Matanuska Glacier and that 5 people died in a helicopter crash skiing near the Knik Glacier. It is so painful when these accidents hit close to home. Our thoughts are with the families, friends, responders and all those affected at this difficult time.
  • Heads up if you are thinking of going to Hatcher today. Please follow Hatcher Pass Avalanche Center’s social media updates and Alaska 511. There is a storm impacting Hatcher Pass today that will increase the avalanche danger. Travel in avalanche terrain is not recommended and AK DOT will potentially close the road.
Mon, March 29th, 2021
Above 2,500'
2 - Moderate
Avalanche risk
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.
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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.

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

The storm that was forecast for today, that was supposed to be similar to last Thursday’s, is not packing much of a punch so far and doesn’t look very promising. Cloudy skies, very light precipitation and moderate winds seem to be on the menu for today and aren’t expected to raise the avalanche danger. With that being said, paying attention to changing conditions will be important if precipitation rates increase or winds really bump up. If either or both of those things happen, watch for increasing slab development and signs of instability. Yet again we don’t have great surface conditions for new snow to bond with.

Persistent Slabs: You may be experiencing some message fatigue but we hope you keep tuning in. Due to the pattern of small storms, dry spells and flip flopping winds over the last two months the avalanche forecast is sounding pretty dang repetitive. Wind slab… Persistent Slab… Wind slab… Persistent slab. We keep having wind slabs develop over weak layers and transition into persistent slabs as they linger.  Today this is the issue again and there is still the concern of finding a slope where old buried weak layers (facets and buried surface hoar) are reactive under stiffer slabs due to wind-loading. There is a weak layer about a foot down that seems to be our current issue.  The natural avalanches on Raggedtop and the skier triggered slab on Tri Tip last week are unfortunately good examples of what we are talking about.  There is still a possibility a person could trigger one of these persistent slab avalanches. Be on the lookout for areas that were previously wind-loaded and those with any new wind-loading. The most suspect terrain will likely be at upper and mid elevations, especially immediately below ridgelines, in cross-loaded gullies, and below convexities.  These areas are prime slab habitat. As always, use good travel protocol, and think about terrain consequences. This type of avalanche issue might allow you to get well out on the slope before the avalanche releases and it might not be the first person that triggers the avalanche.

Loose snow avalanches: Steep slopes that have been sheltered from the wind have up to a foot of loose snow sitting on top of firm surfaces. We have seen a lot of loose snow avalanches (sluffs) since Thursday, and similar activity will be expected today. Any new snow today will add volume to places with soft snow or easily sluff off of sun crusted southerly slopes. While it is unlikely these loose snow avalanches will be big enough to bury you, they can be dangerous if they drag you into terrain traps like cliffs, trees, rocks, or gullies. If we do get rain below 500′ watch for small roller balls and wet loose avalanches.

Wind effect on the north side of Sunburst, 3.28.21. Look for signs of wind-loading today and avoid travel on steep slopes with stiff snow. 

Forecast snow totals through tomorrow afternoon. Do a little snow dance and hope we get some snow!

Mon, March 29th, 2021

Yesterday: Skies were partly cloudy becoming overcast. Winds were light westerly and then shifted to the east in the late afternoon and increased overnight blowing 10-15 mph with gusts into the 20s. Temperatures were in the teens and 20°Fs in the alpine and the mid 20°Fs to mid 30°Fs at lower elevations. Very light snow showers started last night with minimal accumulation. Overnight temperatures were in the high teens to high 20°Fs.

Today: Cloudy skies with light rain and snow showers. Rain/snow line is forecast to be around 500′. Temperatures will be in the high 20°Fs to mid 30°Fs at sea level and mid 20°Fs to to mid teens in the alpine. Winds will be southerly 10-15 mph with gusts into the 20s. Cloudy skies and snow showers continue overnight with temperatures in the mid teens to mid 20°Fs. Winds will remain southerly 10-15 mph with gusts into the 20s.

Tomorrow: Mostly cloudy skies with a chance of snow showers. Temperatures will be in the mid 20°Fs to mid 30°Fs. Winds will be light and easterly.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25 1 0.1 112
Summit Lake (1400′) 24 trace trace 48
Alyeska Mid (1700′) 25 1 0.02 117

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14 WNW-SE* 8 26
Seattle Ridge (2400′) 19 WNW-SE* 7 20

*Wind shift in the late afternoon yesterday.

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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.