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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 14th, 2022 - 7:00AM
Expires
Sat, January 15th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

Today’s avalanche danger is CONSIDERABLE above 1000′, and it is likely a person could trigger an avalanche 2-5′ deep or deeper following yesterday’s heavy snowfall and continued strong winds today. Human-triggered avalanches will be most likely on wind-loaded slopes, but it will also be possible to trigger a large avalanche on protected slopes, failing on weak snow buried earlier this week. Be conservative with your terrain choices, avoiding traveling on or below steep slopes.

The danger is MODERATE below 1000′, where mixed snow and rain during the storm mean potential avalanches will be smaller and more difficult to trigger. Pay attention for warning signs of instability like shooting cracks, collapsing, and fresh avalanches, and be aware of the potential for large avalanches in higher elevations running into low-elevation runout zones.

*Roof Avalanches: Roofs are likely to continue shedding snow today as warm temperatures continue. Keep an eye on children and pets, and be mindful of where you park your vehicle.

 

SEWARD/LOST LAKE: Heavy snowfall continues in these areas this morning, and 24-hour totals are expected to approach 2’ in the upper elevations by the end of the day. Very dangerous avalanche conditions exist in the mountains near Seward, Lost Lake, and Snug Harbor. Travel in avalanche terrain is not recommended.

 

Special Announcements

In case you missed it: You can watch the recording of John’s interview with Pascal Haegeli here. They discussed challenges with risk communication and ways to improve the avalanche advisory. It’s worth watching if you weren’t able to tune in live!

Fri, January 14th, 2022
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
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.
Recent Avalanches

Seward Highway: Natural avalanches ran to the valley in multiple paths along the Seward Highway just south of Girdwood yesterday.

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

We are looking at another day of dangerous avalanche conditions as a strong storm system finishes this morning. Yesterday’s heavy snowfall brought another 1-2′ snow to the mountains around Girdwood and Turnagain Pass, with higher totals near Portage and Placer. The Turnagain Pass snotel site at Center Ridge recorded 0.1″ Snow water equivalent (SWE) per hour for 12 straight hours yesterday. This storm came on the heels of another system that brought heavy snowfall earlier this week, resulting in the following accumulation since Sunday night:

  • Turnagain Pass: 2.2″ SWE, 2-3′ snow above 1500′
  • Alyeska Mid: 3.4″ SWE, 3-4′ above 1500′
  • Summit Lake: 0.6″ SWE, 6-8″ snow

This snow came with strong easterly winds. The Sunburst weather station recorded winds of 40-60 mph yesterday,  gusting to 93 mph and six consecutive hours of gusts from 80-90 mph. The winds have died down slightly this morning, but strong easterly winds are expected to continue at 20-30 mph with gusts of 35-50 mph for most of the day today. This makes large human-triggered avalanches likely.

It is most likely a person will trigger an avalanche on steep, wind loaded slopes at and above treeline. Wind slabs are expected to be in the neighborhood of 2-5′ deep or deeper, and have likely formed a bit further below ridgelines with the strong winds we have been recording. You can also expect to find reactive wind slabs on convex rolls and in steep gullies. Dangerous avalanche conditions mean it is important to choose your terrain wisely. Today this means avoiding traveling on or below steep slopes, and as always, keeping an eye on your partners.

Strong winds at the Sunburst station yesterday. Winds have died down a bit, but are expected to continue at 20-30 mph today with gusts at 35-50 mph.

 

Avalanche Problem 2
  • 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 storm has built thick slabs on a variety of weak surfaces. The most problematic we have seen so far is a layer of facets that formed on top of the New Year’s crust during last week’s clear and cold weather, which is now buried 2-5′ deep or deeper. We have seen this layer showing poor stability in our test pits, and it was failing on small test slopes yesterday in the Tincan trees (more info here). This layer has seen significant loading this week, which increases the likelihood of triggering an avalanche on it. In addition to the wind-loading mentioned in problem 1 above, it may be possible to trigger a large avalanche on steep sheltered slopes, where the layer is 2-3′ deep. There is a higher level of uncertainty associated with these potentially very large avalanches, which gives one more reason to dial back terrain choices today, avoiding traveling on or below steep slopes.

Poor stability test results on a weak layer of facets buried 2-3′ deep in the mid elevations at Tincan yesterday. This layer was breaking on some test slopes nearby during the day. 01.13.2022

Weather
Fri, January 14th, 2022

Yesterday: Heavy snow brought 14-18″ to Turnagain Pass, 18-24″ to Girdwood, and 4-8″ to Summit Lake, with rain up to around 1000′. Strong easterly winds were blowing 40-60 mph with gusts of 80-90 mph at ridgetops. Temperatures remained in the upper 20’s to low 30’s F through last night.

Today: Snowfall is tapering off this morning, but another 1-4″ is possible in Girdwood, with up to 6″ in Portage and Placer. Easterly winds will be sustained at 20-30 mph with gusts of 30-50 mph. Mostly cloudy skies will start to break up in the afternoon, with some pockets of sun possible before the end of the day. Rain level is expected to drop back to 400′ as the snow passes.

Tomorrow: Low temperatures will get down to the low to mid 20’s F overnight, with highs tomorrow in the mid 20’s to low 30’s F. Light winds will stay down at 5-10 mph with variable direction, and light snow could bring 1-3″ to sea level. Skies will be mostly cloudy.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32 12 1.2 85
Summit Lake (1400′) 30 3 0.2 28
Alyeska Mid (1700′) 31 14 1.2 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 ENE 40 93
Seattle Ridge (2400′) 25 SE 15 36
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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.