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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, April 4th, 2022 - 7:00AM
Expires
Tue, April 5th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′. Light winds and snow showers later in the day should not be enough to elevate the avalanche danger, but it is still possible to trigger an avalanche around a foot deep where last week’s snow is sitting on weak surfaces. There is also still a lingering possibility of triggering an avalanche 3-6′ deep on deeper weak layers that were buried last month. If you are trying to get into steep terrain today, take the time to evaluate the snowpack for any warning signs of unstable snow, and be careful with your terrain selection. The avalanche danger is LOW below 1000′.

Special Announcements
  • South Fork of Eagle River Avalanche (3 Bowls):  Crews continue to work to remove the avalanche debris covering Hiland Road and the Municipality of Anchorage has a dashboard with this information. The Municipality of Anchorage is asking the public to stay away from the immediate slide area. It is important to give the workers a safe space to clear the road.
Mon, April 4th, 2022
Alpine
Above 2,500'
2 - Moderate
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: There were two more avalanches reported yesterday in Todd’s bowl that we did not see while we were out on Saturday. It is unclear when they released, but it would have been sometime between Saturday afternoon and Sunday afternoon. There was also a small glide release in the steep south-facing terrain below Hippie Bowl. More details here.

Recent avalanche debris at the bottom of Todd’s Run, and another fresh avalanche on the west facing sub-ridge on the north end of the bowl. Photo: Andy Moderow. 04.03.2022

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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 6-18″ storm snow that fell on Friday is still the main concern for avalanche activity today. The storm buried a layer of surface hoar and near-surface facets that were very touchy on Friday and Saturday, especially in areas that got the most snow during Friday’s storm. While we were out yesterday, we saw encouraging signs that this layer is healing (details here), but it is still going to be possible to trigger an avalanche on it today.

Luckily these persistent weak layers closer to the surface tend to give warning signs when conditions are unstable, so if you are on the lookout you should be able to evaluate the snowpack for dangerous conditions. Watch for the classic red flags– shooting cracks, collapsing, and fresh avalanche activity– as indicators of poor stability. If you notice any of these signs, stick to low slope angles to stay out of harm’s way. Since we are dealing with a relatively shallow weak layer, it is also really easy to evaluate stability with quick travel tests like hand pits and test slopes. Conditions are not as touchy as they have been for the past few days, but if you are trying to get into steep terrain, you are going to want to do your homework. Keep in mind that this weak layer near the surface is not our only concern when you are choosing your terrain, and there are deeper problems that can lead to much bigger avalanches. More on this in problem 2 below.

Tonight it is looking like we are returning to a more active weather pattern over the next few days that will bring another round of moderate winds and light snowfall. Be sure to stay tuned for more updates as conditions change.

Wet Loose Avalanches: We can expect to see some wet loose activity as slopes heat up during the day. The extent of the wet snow problems will depend on how quickly the clouds move in this afternoon. Pay attention to roller balls and pinwheels as signs that wet snow avalanches are becoming possible. It is possible that a loose wet avalanche could trigger a bigger slab as it moves downhill.

Glide Avalanches: We continue to see glide cracks open up, with occasional glide avalanches releasing. This type of avalanche is large, destructive, and unpredictable, so be sure to avoid spending time below glide cracks.

Avalanches similar to this remotely triggered avalanche in Tincan’s Common Bowl on Saturday will still be possible today. 04.02.2022

Glide release on the south side of Tincan Ridge yesterday afternoon. Photo: Allen Dahl. 04.04.2022

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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

Multiple layers of surface hoar and near surface facets are buried 3-6 deep in the snowpack. We have not seen avalanches on these layers over the past week, but we are still keeping them in mind, as they are occasionally producing concerning results in stability tests (details in this video from Tincan yesterday). There is the potential that an avalanche in the upper snowpack (See problem 1 above) can step down and trigger one of these deeply buried layers.

A deep slab is a hard problem to manage. There may be no signs of instability associated with these layers, and multiple people may get away with riding steep terrain and not triggering an avalanche. However, if someone finds a thin spot and is able to collapse a weak layer, it may propagate out to deeper snow and produce a huge avalanche. A trigger spot may even above, below or to the side of the avalanche.

The potential to trigger a big avalanche exists, so keep that in mind as you travel through the mountains today. Choose terrain in your favor by avoiding slopes that would increase the consequences of triggering a large avalanche. This includes big, steep slopes, as well as things like trees, cliffs, rocks, and gullies. You can stick to low angle slopes that are not connected to or underneath steep slopes to avoid the problem entirely. These deep layers need a bit more time stabilize, but things are looking hopeful as we are finding these weak layers to be gaining strength (See our observation from Sunburst yesterday for some details).

This Propagation Saw Test in a snow pit on Tincan yesterday shows the size of the avalanches that may still be possible on those layers of buried surface hoar from last month. Photo: Andy Moderow. 04.04.2022

Weather
Mon, April 4th, 2022

Yesterday: Skies were mostly cloudy around Turnagain Pass, Placer, and Portage, with more sun in the Girdwood area. Winds were light out of the east at 5-10 mph with gusts of 10-20, and the strongest periods in the early afternoon. High temperatures were in the upper 20’s to upper 30’s F, with lows down in the upper teens to mid 20’s F overnight. Light flurries during the day did not amount to any measurable precipitation.

Today: High temperatures should be in the upper 20’s to mid 30’s F with mostly sunny skies in the morning and increasing cloud cover through the day. Winds will once again be light out of the east to southeast, picking up slightly later in the day with sustained speeds of 5-10 mph and gusts of 10-15 mph. Light snowfall may bring a trace of accumulation. Overnight low temperatures are expected to be in the low to mid 20’s F.

Tomorrow: Light snowfall continues tonight into tomorrow, with 2-4″ possible by the end of the day. Snow levels should stay below 300′ with high temperatures in the low 20’s to upper 30’s during the day. It is looking like the easterly winds will increase to 15-25 mph by tomorrow afternoon. Skies will be mostly cloudy during the day, but we might get some occasional sun poking through the clouds.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) N/A* N/A* N/A* N/A*
Summit Lake (1400′) N/A* N/A* N/A* N/A*
Alyeska Mid (1700′) 35 0 0 N/A

*The Snotel network has been down since Friday afternoon.

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 E 4 21
Seattle Ridge (2400′) 25 Var* 2* 4*

*Seattle Ridge was not reporting wind data until 5 p.m. yesterday. Thank you to whoever got up there to knock the rime off!

Observations
Recent Observations for Turnagain Pass
Date Region Location Observer
10/27/24 Turnagain Observation: Tincan Michael Kerst
10/21/24 Turnagain Observation: Turnagain Pass Road Observation Trevor Clayton
10/19/24 Turnagain Observation: Tincan – Below Todds Run Andy Moderow
10/18/24 Turnagain Observation: Taylor Pass Eli Neuffer
10/15/24 Turnagain Observation: Tincan Common John Sykes Forecaster
10/14/24 Turnagain Avalanche: Tincan CNFAC Staff
05/13/24 Turnagain Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South H Thamm
05/13/24 Turnagain Observation: Turnagain Pass non-motorized side Amy Holman
05/12/24 Turnagain Observation: Warm up Bowl Tony Naciuk
05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs A S
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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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