Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, January 8th, 2023 - 7:00AM
Expires
Mon, January 9th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Traveling in the upper elevation backcountry right now follows the advice for CONSIDERABLE avalanche danger; conservative terrain selection and an extra cautious mindset. Two very large slabs were triggered yesterday by skiers, with debris running into valley bottoms and over up-tracks. Triggering a large and dangerous slab is again possible today. Slabs are failing on a buried weak layer 3-6′ deep. They could release after many tracks are on a slope, and be triggered remotely from the top or side of a slope. The danger is MODERATE at treeline for the possibility of smaller slab avalanches to be triggered. The danger is LOW below 1,000′ where crusts exist.

*To avoid this issue, we can stick to slopes 30 degrees or less with nothing steeper above us, including avoiding valley bottoms with large slopes hanging over us.

SUMMIT LAKE / LOST LAKE / SNUG HARBOR: Similar conditions exist across the Kenai with the potential for very large avalanches releasing on buried weak layers. Summit Lake in particular has a very weak snowpack and extra caution is recommended.

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Sun, January 8th, 2023
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Two very large avalanches were triggered yesterday on Cornbiscuit at nearly similar times. One on each side of the ridge (SW facing and N facing). It is looking like they were both triggered due to the same collapse in the snowpack that propagated over the ridge. The SW avalanche caught two skiers with one partially buried, able to self rescue, and is OK. Several people took part is searching the debris with no signals found. We are still gathering details and Andrew will attempt to investigate the avalanche(s) today. Crown depths were ~2-3+’ deep and the likely weak layer was facets on the Thanksgiving crust. Reports sent in HERE and HERE.

Prior to this, no large avalanches were triggered on Friday (one small slab in steep terrain was skier triggered on Tincan), but on Thursday, three days ago, several large slabs were remotely triggered by two snowmachiners in upper Seattle Ck drainage (no one caught).

Large avalanche on the SW face of Cornbiscuit. Many people in the area did an extensive beacon search over the debris with no signals found. Photo by a member of one of the groups in the area, 1,7,23.

 

Avalanche on the north aspect of Cornbiscuit. Debris can be seen that covers an uptrack that people were on just before the avalanche. Photo from a group on Magnum 1.7.23.

 

Closer up view of the left (westerly most) flank of the SW slab. Photo by group in the area 1.7.23.

Another close up on the slab on the SW face, note the several ski tracks from earlier in the day. Photo from another group in the area, 1.7.23.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • Almost 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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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 mountains showed more of their cards yesterday. Dangerously large slabs can still be triggered by people. These slabs are breaking in buried weak layers that can propagate across terrain features and release on all aspects. They look to be releasing around 2,500′ and above. This is the kind of avalanche problem where often no signs of instability are seen, several tracks can be on a slope, making things ‘appear’ OK, and it’s not till someone hits a thin spot that collapses the weak layer and the whole slope releases. Cornbiscuit was the perfect storm and luckily everyone was OK. This type of weak layer is acting up and creating avalanches in ways we have not seen for years. It is proving it can propagate a collapse across various aspects and over ridges, simply scary. After seeing all the large slabs three days ago triggered in Seattle Ck with similar character, we can expect there are more large avalanches waiting to happen in the days ahead.

For anyone headed out today, getting onto large slopes over 30 degrees is a roll of the dice. Yes, there have been a lot of tracks on a lot of steep slopes with no avalanches occurring. This is the MODERATE danger conundrum. Meaning triggering an avalanche is possible, not necessarily likely. What is happening today, and what we have done before, is up the danger for public safety messaging and focusing more on the Travel Advice in the Danger Scale versus the actual avalanche trigger likelihood. Added into the equation is the size of the slabs, they are deadly and unmanageable. They can clearly run into valley bottoms and cover areas that are often relatively safe.

Unfortunately, this issue will likely be with us for a while and we’ll continually be assessing it as best we can. If you are like me, I’m changing my mindset to having fun in low angle terrain for the foreseeable future.

Cornices:  We have only heard of one human triggered cornice fall during the last few days of nice weather. This was on Thursday (1/5), a snowmachiner triggered a cornice, fell off with it, an avalanche was subsequently triggered (around a foot deep) and the rider was carried ~800′. They pulled their airbag, ended up on the surface of the debris and were OK. This report came in a bit late, so if you haven’t seen it the report from that group is HERE. In short, continue to give cornices a berth.

Weather
Sun, January 8th, 2023

Yesterday: Mostly sunny skies were over the region with light westerly ridgetop winds. Temperatures were in the single digits F in valley bottoms and the teens at the mid and upper elevations.

Today: Clouds are forecast to move in today ahead of light snow showers beginning this afternoon. Around an inch of snow could fall tonight. Ridgetop winds are light from the west this morning and will swing around to being light from the east midday. Temperatures are chilly, sitting in the single digits F at sea level and a bit warmer, in the teens, at the higher elevations.

Tomorrow: A few light snow showers look to continue on Monday with some patches of sunny skies possible. Ridgetop winds could begin increasing from the east as the next system is forecast to move in for Tuesday. This should bring several inches of snow and stronger easterly winds. Stay tuned.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 10 0 0 59
Summit Lake (1400′) 0 0 0 32
Alyeska Mid (1700′) 10 0 0 51
Bear Valley – Portage (132′) 16 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14 W 9 15
Seattle Ridge (2400′) 13 N/A N/A N/A
Observations
Recent Observations for Turnagain Pass
Date Region Location
01/29/23 Turnagain Observation: Tincan Backdoor
01/28/23 Turnagain Observation: Sunburst
01/28/23 Turnagain Avalanche: Seattle Ridge
01/28/23 Turnagain Observation: Tincan Common
01/27/23 Turnagain Observation: Sunburst
01/27/23 Turnagain Avalanche: Lynx Creek
01/25/23 Turnagain Observation: Cornbiscuit
01/22/23 Turnagain Avalanche: Tincan
01/21/23 Turnagain Avalanche: Seattle Ridge
01/21/23 Turnagain Avalanche: Lynx drainage – avalanche
Riding Areas
Updated Fri, January 06th, 2023

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Open
Opened Dec 13th.
Placer River
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Skookum Drainage
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Turnagain Pass
Open
Opened Dec 13th.
Twentymile
Closed
Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Seward District
Carter Lake
Open
Opened Dec 13th.
Lost Lake Trail
Open
Opened Dec 13th.
Primrose Trail
Open
Opened Dec 13th.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Open
Opened Dec 13th.
South Fork Snow River Corridor
Open
Opened Dec 13th.
Summit Lake
Open
Opened Dec 13th.

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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.