Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, April 1st, 2022 - 7:00AM
Expires
Sat, April 2nd, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000′. Strong winds and light snowfall are once again burying weak surfaces, making it likely a person can trigger an avalanche 6-12″ deep in Turnagain Pass and Girdwood, and up to 2-3′ deep by the end of the day in Portage and Placer. In addition to the potential for avalanches in the new snow, there is still a possibility of triggering a very large avalanche on a layer of buried surface hoar that is 3-5′ deep. Stay conservative with terrain choices today, including limiting time spent traveling below steep terrain. The danger is MODERATE below 1000′, where the main concerns will be wet snow avalanches and the potential for large avalanches starting at higher elevations and running long distances.

PORTAGE/PLACER VALLEYS: These areas will once again see much higher storm totals than the rest of the advisory area. As the snow piles up during the day, expect to find dangerous avalanche conditions within the storm snow even on slopes that are sheltered from the winds.

Special Announcements

SKOOKUM VALLEY is closed to motorized use as of today, April 1st, due to the National Forest Plan. The boundary extends East of the Railroad tracks from Luebner Lake (South) to private property boundary (North). The rest of the Placer River Valley remains open.

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Fri, April 1st, 2022
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

The wind ramped up overnight, with sustained speeds of 30-50 mph and gusts of 50-65 mph since around midnight. We are looking at 2-6″ snow possible during the day in Girdwood and Turnagain Pass, and up to a foot in Portage and Placer. During the brief spell of clear weather earlier in the week, we saw another round of surface hoar and near surface facets develop once again (see the recent observations from the Placer Valley and Seattle Ridge for details), which covered a crust on sun-exposed slopes. The combination of strong winds and new snow is building sensitive slabs on top of weak surfaces– a formula that has resulted in multiple avalanche cycles in the past month and is likely to produce avalanches once again.

The size of the wind slabs forming today will depend partly on the amount of snow we get. With continued strong winds, we can expect to see slabs forming around a foot deep in the areas that don’t see a lot of snowfall today, and slabs 2-3′ deep in places like Portage and Placer, which could see significant accumulation. It will be important to pay attention to increasing danger during the day. In the zones that are seeing the heaviest snowfall, we will likely see storm slabs getting deep enough to bury, injure, or kill a person even on slopes sheltered from the wind, and we can expect them to be very reactive given the fresh layer of surface hoar and near-surface facets that just got buried.

These fresh wind and storm slabs tend to give us warning signs that conditions are unstable. Be on the lookout for shooting cracks, collapsing, and fresh avalanches as indicators of dangerous avalanche conditions, and avoid steep terrain if you see any of the above. Keep in mind these relatively small avalanches near the surface have the potential to step down to deeper weak layers buried last month, resulting in a much larger and more destructive event. More on this in problem 2 below. Look for the safest conditions (and the best quality snow) on lower angle slopes that are protected from the wind, and avoid terrain that tends to produce wind slab avalanches. This includes steep terrain near ridgelines, convex rolls, and steep gullies.

A familiar narrative- a fresh layer of surface hoar formed during a brief clear spell before this last storm and is currently getting buried. This will make the new snow extra touchy today. Photo taken by Graham Predeger in the Placer Valley area on Wednesday. 03.30.2022

Cornice Fall: Cornices will be growing and stressed today, increasing the chances of natural cornice failure. We have seen multiple recent avalanches triggered by cornice falls, including one very large avalanche on Magnum earlier in the week. As always, limit time spent below cornices, and be sure to give them plenty of space if you are travelling along ridgelines.

Loose Wet Avalanches: With little or no refreeze overnight, and light rain expected during the day at lower elevations, wet loose avalanches should be on your radar today. These are typically slow moving and avoidable if you are paying attention, but can be dangerous if they catch you off guard from above, or if they were to push you into traps like gullies, trees, rocks, or cliffs.

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

Today’s loading event will be adding stress to a snowpack with multiple problematic weak layers buried 3-5′ deep or deeper. Although the smaller storm totals are unlikely to result in a widespread natural cycle on these deeper weak layers, the load will be nudging the needle towards instability. As mentioned above, a relatively small avalanche triggered near the surface has the potential to step down to one of the three layers of surface hoar that got buried last month, making for a very large and destructive avalanche.

Deep slab avalanches have some nasty characteristics. They rarely give any feedback of unstable conditions prior to avalanching, which can make them difficult to predict. They are also vey stubborn, which can allow for multiple sets of tracks on a slope prior to avalanching. With this setup especially, we have seen really well connected slabs propagating wide distances over large terrain features. This wide propagation means that avalanches can be triggered remotely– from below, above, or next to the slope that releases.

Because of the size and unpredictability of these very large avalanches, it is important to keep your terrain choices mellow. Pay attention to the terrain you are traveling under, as well as the slopes you are considering skiing or riding on. To avoid this problem, stick to lower slope angles that are out of the way of steep overhead terrain. This setup is concerning, and with a new loading event and fresh avalanches expected near the surface today, it is very important to keep these deeper weak layers in mind.

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Weather
Fri, April 1st, 2022

Yesterday: Skies were mostly cloudy with moderate easterly winds at 10-20 mph for most of the day, increasing to 30-50 mph and gusting 50-65 mph overnight into this morning. Highs temperatures were in the mid 20’s to upper 30’s F, with overnight lows in the low 20’s to low 30’s F. Weather stations are showing a trace of precipitation this morning, with rain levels estimated around 1000′.

Today: Strong winds will be the main event today, with most of the advisory area seeing continued sustained easterly winds at 20-30 mph with gusts of 30-45 mph. Girdwood and Turnagain Pass may see 2-4″ snow, while 10-12″ is expected in Portage and Placer. The rain level should drop down to 100-300′, with high temperatures in the upper 20’s to mid 30’s F. Temperatures are expected to drop down into the 20’s F overnight.

Tomorrow: Snowfall continues overnight, with another 2-3″ in Girdwood and Turnagain Pass, and 12-15″ possible in Portage and Placer before clouds start to break up during the day tomorrow. Winds are looking to back down slowly overnight, with sustained speeds of 15-20 mph out of the east, and continue to taper down to 5-10 mph by tomorrow afternoon.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35 1 0.1 117
Summit Lake (1400′) 35 0 0 40
Alyeska Mid (1700′) 34 1 0.1 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 NE 26 66
Seattle Ridge (2400′) 25 SE 16 31
Observations
Recent Observations for Turnagain Pass
Date Region Location
05/11/22 Turnagain Avalanche: Cornbiscuit and Magnum west faces
05/07/22 Turnagain Observation: Granddaddy
04/29/22 Turnagain Observation: Sunburst wx station
04/28/22 Turnagain Observation: More Turnagain Pass/Summit Lake wet slab activity
04/27/22 Turnagain Observation: Magnum
04/27/22 Turnagain Observation: Girdwood/Summit/Turnagain Road obs
04/24/22 Turnagain Avalanche: Seattle Ridge – large glide avalanche on Repeat Offender path
04/24/22 Turnagain Avalanche: Seattle Ridge uptrack
04/24/22 Turnagain Observation: Pastoral
04/24/22 Turnagain Observation: Sunburst
Riding Areas
Updated Fri, May 13th, 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
Closed as of May 1 per Forest Plan.
Placer River
Closed
Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage
Closed
Closed as of April 1st per Forest Plan.
Turnagain Pass
Open
Open. Extended opening through May 31.
Twentymile
Closed
Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake
Closed
Closed as of May 1 per Forest Plan.
Lost Lake Trail
Closed
Closed as of May 1 per Forest Plan.
Primrose Trail
Closed
Closed as of May 1 per Forest Plan.
Resurrection Pass Trail
Closed
Closed as of May 1 per Forest Plan.
Snug Harbor
Closed
Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor
Closed
Closed as of May 1 per Forest Plan.
Summit Lake
Closed
Closed as of May 1 per Forest Plan.

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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.