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 22nd, 2023 - 7:00AM
Expires
Mon, January 23rd, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is expected to rise to HIGH today above 2,500′ due to strong ridgetop winds and snowfall. Large natural slab avalanches (2-3+ feet deep) will likely occur at the high elevations while human triggered slabs will be very likely to trigger. The danger is CONSIDERABLE below 2,500′ where natural avalanches are possible yet human triggered avalanches remain likely. Travel in avalanche terrain is NOT recommended. Also, debris from avalanches releasing above could run into the lower elevations.

SUMMIT LAKE / SNUG / LOST LAKE:  A dangerous snowpack exists in these areas as well. Two avalanches were triggered by skiers on Butch Mtn in the Summit Lake area yesterday. Skiers were able to escape being caught. The report is HERE.

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Sun, January 22nd, 2023
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

We heard of three large human triggered avalanches and a couple of smaller ones yesterday. There were also two large natural avalanches that likely occurred sometime late on Friday or early yesterday morning as the last weather system moved out. All these slabs appear to have failed in the buried surface hoar that ranges from 1.5-3′ deep in the snowpack.

SW face of Cornbiscuit:  One skier caught, carried, partially buried. Injured elbow, group was able to self rescue. This was a slab around 2′ deep with wide propagation, running 1,500, and looks to have overrun portions of the large slab triggered on this face two weeks ago. A second avalanche was triggered by second skier descending, skier was not caught. Report from group involved HERE. Report from near miss two weeks ago HERE.

Seattle Ridge, Warm Up (-1 Bowl):  We heard second hand by a couple people that an avalanche was triggered that caught a person who was carried and partially buried. We hope to find out more today. Send us an email (staff@chugachavalanche.org) or observation if you have any info, thanks!

Pete’s North:  Group of three skiers ascending triggered a slab avalanche in an open area in the trees. This was at an elevation around 1,400′ and slab was around 18″ deep. No one caught. Report by group HERE.

Natural Avalanches:  One in Todd’s Bowl, very wide propagation, including pulling out sections lower on slope. And one on the roadside (SE face) of Seattle Ridge, also showing wide propagation. Both of these can be seen HERE.

 

Skier triggered slab on the SW face of Cornbiscuit. This also includes the section that was triggered by the second skier. Photo by party involved, 1.21.23. 

 


Pete’s North slab avalanche triggered by group on edge of meadow. Photo by party involved, 1.21.23.

 

Todds Bowl natural avalanche, occurring sometime late Friday night or early yesterday morning. Andy Moderow 1.21.23. 

 


The other large natural avalanche on the road side of Seattle Ridge. Also showing a wide propagating crown. Photo Elias Holt, 1.21.23.

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

Despite so many folks playing it safe yesterday, the snowpack was touchy enough that several people were still able to trigger avalanches. Some of these quite large and dangerous, such as the slab on the SW face of Cornbiscuit. This is all due to a layer of buried surface hoar that is still proving to be reactive. Today, more weather is headed in that will continue to load, and likely overload, the weak layers giving us so much grief.

Although we should only see 4-6″ of new snow today, the ridgetop winds will be the big player. They are slated to blow 35-45mph from an easterly direction with gusts near, or more than, 60mph. Wind slabs will be developing easily in the upper elevations, and possibly in exposed areas in the trees as there is plenty of soft snow to transport. Wind slabs are an issue on their own, but more concerning is the layer of buried surface hoar, 1.5-3′ deep, that is still producing avalanches. Hence, a smaller wind slab could trigger a much larger slab, or simply a wind loaded slope could release a larger slab that breaks 3 or so feet deep from the start. All these options are dangerous.

For today, visibility should be poor with the storm, limiting easy travel to the higher elevations, but these issues also exist in the mid elevations. As seen in the Pete’s North slab, even open slopes in the trees are suspect for triggering a slab avalanche we don’t want to be caught up in. That said, a very cautious mindset and careful route-finding is necessary if headed out to treed zones that may often seem safe. To reiterate, travel in avalanche terrain is NOT recommended.

 

This is a photo of the looker’s left side of Todd’s Bowl, lower on the slope where debris from the main avalanche was able to trigger this slab. This is indicative of a buried persistent weak layer, in our case now, the 1/10 buried surface hoar. Photo Andy Moderow, 1.21.23.

 

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Aspect/Elevation
  • Almost 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.

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

From what we know yesterday, no recent avalanches have broken in our notorious deep persistent weak layer. This is the Thanksgiving facet/crust combo near the base of the snowpack; it’s anywhere from 4-8′ deep now. The layer is becoming deeper and deeper as more snow falls, making it less likely to be triggered, but we are still not writing it off. It’s hard to know if wind loading, or an avalanche breaking on the buried surface hoar, could trigger a very deep slab or not. This clearly would create a very large slide. But either way, the issues in the top 3′ of the snowpack are worrisome enough.

Weather
Sun, January 22nd, 2023

Yesterday:  Sunny skis were over the region yesterday. Ridgetop winds were breezy (10-20mph) from the NW with some areas seeing stronger gusts. Temperatures dropped to 15-20F at the mid and upper elevations.

Today:  A storm system is headed in this morning. Strong winds and light snowfall should develop through the day. Around 4-6″ of snow is forecast with a rain/snow line around 500′. Ridgetop winds should pick up into the 35-45mph range with gusts in the 60’s or more from an easterly direction. Temperatures are warming after yesterdays dip and should be in the mid 30’sF at the mid elevations and mid 20’sF along ridgelines.

Tomorrow:  The storm moves out tomorrow with decreasing easterly winds and only around a trace of snow expected. Temperatures will be on the rise however as warm air filters in from the Gulf of Alaska. Periods of light snow (rain below 1,000′) should persist for the early part of the week.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25 0 0 67
Summit Lake (1400′) 18 0 0 33
Alyeska Mid (1700′) 24 0 0 67
Bear Valley – Portage (132′) 28 rain 0.2

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 18 W>NE 8 28
Seattle Ridge (2400′) 20 N>SE 7 23
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.