Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, December 2nd, 2022 - 7:00AM
Expires
Sat, December 3rd, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 2500′ today. Lingering wind slabs up to 1′ deep are still possible for a person to trigger. These are most likely at upper elevations, especially along ridgelines and cross loaded gullies. Additional concerns include loose snow avalanches in steep terrain and a weak layer on the ground that could produce larger avalanches at upper elevations. Below 2500′ the avalanche danger is LOW.

Special Announcements
  • Public Service Statement:  We got word of a dog running into the highway from the Tincan parking lot that almost caused a motor vehicle accident yesterday. Just a friendly reminder to keep your dogs close and on leash when near the highway. We are so happy everyone is fine, including the dog!
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Fri, December 2nd, 2022
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
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
Low (1)
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

The last known avalanche observations were natural wind slabs that occurred during last weekend’s outflow wind event on 11/25 to 11/26.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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.

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

Lingering wind slabs that formed during yesterday’s NW outflow wind event are the primary concern for today. Those wind slabs likely formed up to 1′ deep on top of weak faceted surface snow, which can cause them to remain reactive for longer than normal. They are most likely to be found along upper elevation ridgelines, on convex features, and in cross loaded gullies. Keeping a close eye on the surface conditions around you and stepping out of the skin track to feel for stiff and hollow feeling wind transported snow is a good way to identify wind slabs in the terrain.

In addition to wind slabs, the surface snow has been loosing strength over the past week and turning into facets under the clear skies. We have observed some large skier triggered loose snow avalanches (aka sluffs) that could knock a person off balance in steeper terrain. Heads up to try and manage sluff by stopping and letting it go by you or skiing across the fall line to allow it to run beside you.

Mixture of weak surface snow (surface hoar and surface facets) that could be buried by a wind slab after yesterdays outflow wind event. Photo 11.30.22

Avalanche Problem 2
  • 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

A layer of faceted snow on the ground at upper elevations continues to be on our radar, despite being over two weeks since the last avalanche activity on this layer. This persistent weak layer could produce avalanches 2-4′ deep, but it is currently unlikely for a person to trigger an avalanche on this layer. Part of the reason we are still concerned about this layer is that the snowpack depth at upper elevations remains thin and variable, with only 1-3′ of total snow depth in many areas. That means it would be relatively easy to find a spot where the weight of a person could initiate a failure on this persistent weak layer.

The other main reason is that we still don’t have a lot of information about the snowpack structure and general conditions from the higher alpine elevations of the forecast region. Some of our observations over the past week have indicated that this layer is gaining strength and others indicate that it is well preserved and just waiting for a new snow load to potentially become active again. We are seeking more information from high alpine areas to help fill our knowledge gaps, so please submit an observation if you are able to look for this layer at the base of the snowpack above 3000′!

Weather
Fri, December 2nd, 2022

Yesterday: NW outflow winds were the main weather feature yesterday. In areas exposed to gap winds, like along Turnagain Arm and higher elevations, wind speeds averaged in the 15-20 mph range with gusts up to 50 mph. However, most of the remote weather stations in the region saw much lighter winds, with averages of 5-15 mph and gusts to 20 mph, and were thankfully sheltered from the brunt of the outflow winds. Skies were clear and temperatures stayed in the 10-20 F range.

Today: Winds are expected to be light today, with averages in the 5-10 mph range. Skies will be mostly clear with some bands of high clouds possibly moving through the area. Another temperature inversion has set up, with current temperatures in the single digits at lower elevations and twenties at ridgelines. This inversion is expected to persist through Saturday.

Tomorrow: Saturday looks largely similar to Friday with light winds expected. Mostly clear skies with some bands of high clouds. Temperatures are expected to increase on Saturday to 15-25 F at lower elevations and 20-30 F at upper elevations. No precipitation is expected until Monday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 13.5 0 0 23
Summit Lake (1400′) 6 0 0 15
Alyeska Mid (1700′) 13 0 0 20
Bear Valley (Portage) (132′) 12 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17 WNW 9 20
Seattle Ridge (2400′) 15 N 4 13
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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.