Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, March 22nd, 2022 - 7:00AM
Expires
Wed, March 23rd, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE on all aspects above 1,000′. Triggering a slab avalanche that fails on a buried layer of surface hoar between 1 and 2 feet deep is still possible. Additionally, watch for fresh wind slabs to be forming in the upper elevations due to a bump in easterly ridgetop winds accompanied with a couple inches of new snow.

*A multi-day series of storms is moving in with the strongest wave hitting Thursday. Avalanche danger will be rising over the next couple days due to expected heavy snowfall and strong winds. Be sure to pay attention to changing conditions across the region.

Special Announcements
  • A BIG THANK YOU to everyone who joined us for the 2022 Turnagain Pass Avalanche Awareness Day last Saturday!! Check out the photos and highlights HERE. Special thanks to the Anchorage Nordic Ski Patrol for providing and manning the beacon park!
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Tue, March 22nd, 2022
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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

We had reports of 3-4 new slab avalanches triggered in the Seattle Creek area yesterday. No one is known to have been caught in any of them. The photo below is one of these slabs that occurred on the Seattle Creek Headwall (NE, 3,500′). The avalanche released after several tracks were on the slope. All the slabs reported are believed to have failed on the March 16th layer of buried surface hoar (12-16″ deep in this area). This is the same layer that is responsible for all the human triggered avalanches over the weekend.

Slab avalanche triggered yesterday on the Seattle Headwall (far east corner of the headwall, NE, 3,500′). Photo: Adam Hoke 3.21.22.

 

This is the same avalanche, looking up at the crown. Photo: Adam Hoke, 3.21.22.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • 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.

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

After three glorious sunny days, clouds have moved in overnight ahead of a long duration weather event that could last through Friday. Today we should see light snowfall, adding anywhere from 1-3″ through the day – snow to sea level. Ridgetop winds will be rising into the 20’s mph from an easterly direction with gusts into the 40’s at times. With just a little new snow, it will be the bump in winds that could create some new avalanche issues over the old one. These are new shallow wind slabs that could form in the higher terrain. The old issue is the buried surface hoar that sits 1-2 feet deep and is still creating avalanches.

Persistent Slab Avalanches:  If you are headed out today and visibility is good enough to get into the bigger terrain near and above treeline, remember that somewhere in the top 2 feet of the snowpack is likely a layer of buried surface hoar. This layer has proved that it can still be triggered by people and this is our main concern until the next round of storms really gets going. The most likely places to trigger one of these slabs is on the more shaded slopes that do not have sun crusts. Tracks on a slope do not mean it’s safe, as was seen in the avalanche pictured above. These types of avalanches are tricky so we need to be extra cautious and remember, we may not get any red flags until a slope slides. This is also a reason to stick to our good travel protocol (exposing only one person at a time, having escape routes planned, and watching our partners closely). To avoid the issue all together, sticking to terrain 30 degrees or less is always a safe bet.

New Wind Slabs:  Another thing to watch for today is active wind loading. There is plenty of soft surface snow to blow into shallow wind slabs if the winds verify. Right now, it looks like the wind should be hitting mostly the high elevation terrain. Any fresh wind slab could be quite touchy as it could be forming over a new batch of surface hoar. The winds themselves will be the biggest clue to new wind slabs, but also watch for cracking in the snow around you and hollow feeling snow.

 

A new crop of surface hoar has been forming over the past couple days. This has been observed on all aspects and elevations. 3.21.22.

Looking ahead to this next round of precipitation and wind, we are not expecting the new snow to bond well to the old surface. This is due to the new layer of surface hoar of course, but also due to near surface facets and sun crusts that have formed. All these layers will be suspect once the snow starts piling up. That could be as early as tomorrow, but more likely on Thursday.

Glide Avalanches:  Although there are many glide cracks slowly opening, we know of only one release recently. That was on the west side of the Girdwood Valley over the weekend. As spring continues, glide cracks typically begin releasing. This is something to keep in mind moving forward.

Glide crack on the lower SW face of the Wolverine ridgeline. 3.21.22.

Weather
Tue, March 22nd, 2022

Yesterday:  There was not a cloud in the sky yesterday to welcoming in Spring. Ridgetop winds were light from the east/northeast. Temperatures climbed into the 30’sF at most locations, save for the high terrain, in the afternoon before cooling into the 20’sF overnight.

Today:  Clouds have been streaming in ahead of a multi-day series of storms. The first wave is today with 1-3″ of snow forecast to sea level. Ridgetop winds will be climbing into the 20’s mph with gusts into the 40’s. Mountain temperatures should stay fairly cool, in the 20’sF.

Tomorrow:  The second wave of precipitation looks to hit early tomorrow morning, Wednesday. Temperatures will be on a slow rise along with the easterly winds and heavier snowfall. We could see anywhere from 3-6″ through the day. The storm is forecast to peak on Thursday with over a foot of snow expected above 800′. Stay tuned!

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 23 0 0 93
Summit Lake (1400′) 21 0 0 39
Alyeska Mid (1700′) 28 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19* NE* 8* 20*
Seattle Ridge (2400′) 22 variable 3 7

*Sunburst weather station is back online (averages are only the last 14 hours).

Observations
Recent Observations for Turnagain Pass
Date Region Location
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Sunnyside / Seattle Ridge
11/25/22 Turnagain Observation: Sunburst
11/25/22 Turnagain Observation: Tincan Trees
11/25/22 Turnagain Observation: Tincan
11/25/22 Turnagain Observation: Top of Seattle Ridge uptrack
11/24/22 Turnagain Avalanche: Sunnyside/Main Bowl
11/23/22 Turnagain Avalanche: Seattle Ridge
11/23/22 Turnagain Observation: Tincan Trees
11/23/22 Turnagain Observation: Tin Can Common Bowl
Riding Areas
Updated Sat, November 26th, 2022

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
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass
Closed
The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.

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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.