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 8th, 2022 - 7:00AM
Expires
Sat, April 9th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1000′ today. Light snowfall with increasing northwesterly winds through the day will build fresh wind slabs, making it possible to trigger avalanches up to a foot deep on wind loaded slopes. There is a smaller chance of triggering an avalanche on deeper weak layers buried 1-2′ deep. The danger is LOW below 1000′, where it is unlikely a person will trigger an avalanche.

 

SEWARD/LOST LAKE/SNUG HARBOR: These areas will see northwest outflow winds pick up earlier today than our core advisory area. Be aware of increasing avalanche danger as strong winds move snow around, especially at higher elevations.

 

Special Announcements

Crews from Chugach Electric will be checking the power lines along the non-motorized side of Turnagain Pass on snowmachines today. They will be riding along the power lines between the Center Ridge parking lot and the Johnson Pass trailhead.

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Fri, April 8th, 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)
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

A low pressure system sitting over Prince William sound is expected to bring light snowfall to the area today, with increasing northwesterly winds as the system passes and outflow winds pick up behind it. Snow totals are looking to be around 1-3″ for most areas, with winds around 15-20 mph at upper elevations by this afternoon. The combination of a few new inches of snow on top of last week’s storm snow will provide plenty of ammunition for the winds to build reactive wind slabs. Since the winds will be coming out of the northwest, they will be more efficient at picking up snow from cold and shaded slopes with dry snow at the surface, and load it on southerly slopes with crusts at the surface. This will most likely mean fresh wind slabs may be more reactive than usual, and they may hang around a little bit longer than usual.

Wind slabs forming today might not be huge, but they may be approaching sizes large enough to bury or injure a person. Keep in mind even small avalanches can have serious consequences in big terrain, and choose your terrain accordingly. Be on the lookout for telltale signs of unstable snow– shooting cracks, collapsing, and fresh avalanche activity. Because of the way local terrain channels winds, these northwest wind events can have some funky wind patterns in the Turnagain Pass area. This pattern commonly results in northern winds along the motorized side of the highway with southerly winds along the skier side, and winds can switch directions as you gain elevation. Be on the lookout for wind slabs potentially forming on all aspects today, and take the time time to assess stability before getting into steep terrain.

Glide Avalanches: We are continuing to see glide avalanches release in the area, with the most recent activity along the Seward Highway yesterday just north of Girdwood. These avalanches are very large and unpredictable, so limit the amount of time you spend under them.

Dry Loose Avalanches: For slopes that stay protected from the winds, pay attention to sluffing in steep terrain. These may be easy to trigger and fast-moving on southerly slopes where new snow is falling on firm surfaces.

Northwest outflow winds are on the way. Winds should start picking up this afternoon, with sustained speeds of 15-20 mph by the end of the day. Source: NAM model on Windy.com.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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 weak interface that was buried on April Fool’s day is becoming less likely to produce avalanches, but should still be on the radar today. The most recent avalanche activity on this interface was a skier-triggered avalanche on a northeast-facing slope in the Seattle Creek drainage on Monday. Keep this layer in mind while navigating the mountains today, and play the terrain in your favor by avoiding slopes with exposure to terrain traps that increase the consequences of getting caught in an avalanche. This includes things like cliffs, trees, rocks, and gullies. This layer is becoming more difficult to trigger, but it is still worth considering today.

Unstable test result on the 4/1 interface on a s-facing slope at around 2000′ in the Squirrel Flats area. 04.05.2022

Weather
Fri, April 8th, 2022

Yesterday: Skies were mostly sunny with light winds out of the east for most of the day before switching westerly overnight. Sustained speeds were around 5 mph with gusts of 5-10 mph. High temperatures were in the upper 30’s to low 40’s F, with overnight lows in the upper teens to upper 20’s F.

Today: Light snowfall is expected through the day, with 1-3″ accumulation by the end of the day. Winds will be light to moderate out of the northwest, with sustained speeds of 5-10 mph for most of the day, increasing to 15-20 this evening. Snow is expected to stay down at sea level, with high temperatures in the low 30’s at low elevations and upper teens at ridgetops.

Tomorrow: Northwest outflow winds continue tomorrow, bringing mostly sunny skies and cooler temperatures than normal. High temperatures should be in the 20’s F, with lows dropping to the single digits to low teens tomorrow night. Winds are expected to be blowing 10-20 mph out of the northwest with gusts of 25-30 mph. We might see a trace of snow overnight tonight, but no precipitation is expected during the day tomorrow.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30 0 0 114
Summit Lake (1400′) 28 0 0 40
Alyeska Mid (1700′) 34 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24 W 4 16
Seattle Ridge (2400′) 27 var 1 6
Observations
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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.