Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, April 24th, 2022 - 7:00AM
Expires
Mon, April 25th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1000′. Storm slabs and wind slabs 1-3+’ deep that formed during the storm over the past 2 days are the primary avalanche problems and are likely to be triggered by a person and possible for natural triggering. Cautious route finding and careful snowpack evaluation is recommended before entering avalanche terrain today. In addition, we could see more wet slab activity especially on south facing terrain in areas with a thinner snowpack that are getting added melt from the sun. Continued glide avalanche activity is also likely and we recommend avoiding spending time underneath glide cracks.

Below 1000′ the avalanche danger is MODERATE. Warm temperatures and rain at lower elevations during the storm have created an unconsolidated wet snowpack that could easily lead to wet loose avalanches in steeper terrain.

MONDAY AVALANCHE OUTLOOK:  There will be no forecast issued tomorrow, Monday. The next forecast will be Tuesday, April 26th at 7am. Avalanche conditions are expected to remain dangerous for wet avalanches, especially in the afternoon on southerly slopes seeing direct sunshine. In the higher elevation shady terrain the danger is trending to MODERATE as storm slab and wind slab avalanches become more difficult to trigger.

Special Announcements
  • End of Season Operations:  Forecasts will be issued on Tuesday, Thursday, Saturday and Sunday through the end of April. If a dramatic change in avalanche conditions occurs on an off day, we will provide a forecast. The final forecast will be on Saturday, April 30th.
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Sun, April 24th, 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)
Recent Avalanches

Lots of new avalanches were observed yesterday that occurred sometime during the storm on Friday or Saturday. There is a mix of large wet slabs that released at lower elevations on more southerly aspects and storm slabs that included just the storm snow above the old melt freeze surface that were releasing naturally yesterday.

Wet slabs along Seattle Ridge: Several new avalanches along Seattle Ridge appeared to be wet slabs caused by melt water percolating through the snowpack, which is typical of the spring shed cycle. These can look similar to glide avalanches but in general the bed surface is not on the ground and they can have different character in terms of propagation across the slope compared to typical glide avalanches.

Large wet slab on Seattle Ridge near the motorized parking lot. Photo from Jason Koenigsberg 4.23.22 

Another large wet slab on Seattle Ridge near Bertha Creek Campground with very dirty debris. 4.23.22

Debris from wet slab pictured above. 4.23.22

Storm slabs releasing at interface with the old melt freeze surface: Despite the low visibility for most of the day yesterday there were a handful of observations of storm slabs releasing in both Turnagain Pass and Portage area. These ranges from roughly 1-3+’ deep depending on wind loading and how much new snow the area received.

Large storm slab at the end of Center Ridge where it turns into Lyon Creek Drainage. Photo Jason Koenigsberg 4.23.22

Several natural storm slabs released on the north aspect of Pete’s South while we were touring on Pete’s N. Photo 4.23.22

Large storm slab crown in Portage area. Photo 4.23.22

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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 spring storm over the past 3 days has forced us out of the easy going spring avalanche mindset and back into a mindset of active natural avalanches and dry snow avalanche problems at higher elevations. Today the storm has ended and we are expecting warm temperatures and broken cloud cover that could lead to more natural and human triggered avalanches at the interface of the new snow and old snow. Warming from the sun and relatively high air temperatures could be enough to cause the new snow to release naturally or be primed for human triggering, as we saw yesterday on Pete’s (see ob here). These spring storms are tricky to predict so we are taking a cautious approach to forecasting the potential for avalanche activity at the interface of the new snow and old snow surface.

The primary avalanche problems today are storm slabs and wind slabs that were created during the storm on Friday and Saturday, and do not seem to be bonding well to the old snow surface. The depth of these avalanches could range from 1-3+’ depending on wind loading and the amount of snowfall received in the area you are travelling. Coastal areas near Portage and Placer received 3+’ of new snow compared to 1-1.5′ for Turnagain Pass and Girdwood. These surface snow avalanches were occurring on all aspects above 1500′ yesterday. The high water content of the new snow means that even a relatively small storm slab or wind slab can be very heavy and have more force than you might expect.

To evaluate whether these avalanches are an issue today keep an eye out for red flags, especially any natural avalanche triggered by warming from the sun, and use test slopes to get a sense for how the new snow is bonding to the old melt freeze surface.

Avalanche Problem 2
  • Wet Slab
    Wet Slab
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wet Slab
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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

In addition to the surface snow avalanche problems, we have also been seeing the beginnings of the spring shed cycle over the past week, with large wet slab avalanches occurring in the Crow Creek area (see obs here and here), Gulch creek (see ob here), and along Seattle Ridge (see ob here). The warm temperatures and rain at lower elevations during the storm have continued to contribute to the wet slab potential and the possible addition of partially sunny skies today will add more melt water to the snowpack. Yesterday the snowpack was saturated below 1500′ where rain had fallen during the storm and there was no crust on the surface.

Most if not all of the wet slab activity we have seen so far is on southern aspects that have an overall thinner snowpack structure. This trend will likely continue, with melt water reaching deeper weak layers in areas with thinner snowpacks that are receiving additional melt water from the sun. We recommend avoiding spending time underneath south facing slopes that are receiving active solar melting today and may not have refrozen over the past two days with the warm temperatures and rain during the storm. It is difficult to predict the exact timing and location of wet slab avalanches, but a lot of the necessary ingredients are available now so a cautious approach to travelling in areas that have similar characteristics to where we have already seen wet slabs is prudent.

Glide Avalanches: The cycle of glide avalanche releases that had started prior to this last storm is likely still active so we recommend avoiding spending time underneath any visible glide cracks.  These can release randomly and are generally very large and destructive avalanches.

Wet Loose Avalanches: Lots of fresh wet loose avalanches were visible yesterday and they were easy to trigger on any steeper slopes. Be aware of the force that wet slab avalanches can contain, especially on long planar slopes where they can pick up a head of steam and entrain a lot of snow.

Weather
Sun, April 24th, 2022

Yesterday: Light to moderate rain up to about 1700′ transitioning to snow above that. Snow totals for the storm range from 1′ to 1.5′ of wet snow over the past 3 days for Turnagain Pass and Girdwood. Coastal areas near Portage and Placer likely received significantly more precipitation over the past 3 days, with up to 3+’ of snowfall. Winds were moderate out of the east in the 5-20 mph range with gusts up to 40 mph.

Today: No significant additional precipitation is expected today, but snow or rain showers are possible especially in coastal areas. Winds should be calm to light in the 0-10 mph range. Broken cloud cover is expected throughout the day with some areas of valley fog this morning. Temperatures are forecast to reach up to the mid 30s F at upper elevations and mid 40s F at lower elevations.

Tomorrow: Tomorrow and the first half of this week are looking very similar to today. With patchy cloud cover, light winds, and warm temperatures.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 37 0 0.4 107
Summit Lake (1400′) 37 0 0.1 33
Alyeska Mid (1700′) 36 0 0.3 NA

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 27 ENE 15 43
Seattle Ridge (2400′) 31 SE 5 16
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.