Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 27th, 2022 - 7:00AM
Expires
Wed, December 28th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains HIGH as a warm storm continues to impact the area. Rain, snowfall, and strong wind has been overloading the snowpack. Many natural avalanches were seen yesterday, which may continue through today. Human-triggered avalanches will be very likely. Travel in and below avalanche terrain is not recommended.

* Roof Avalanches: Light rain and above-freezing temperatures will keep roof avalanches likely through today. Be sure to keep an eye on children and pets, and be careful where you park your vehicles.

Special Announcements

Road Conditions:  Dangerous road conditions were seen along the Seward Highway yesterday from Anchorage to Seward. Checking 511.alaska.gov is one way to keep up to date.

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Tue, December 27th, 2022
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Despite the limited ability to travel along the roads and no known reports from the backcountry, many avalanche paths seen from the highway had fresh debris in them. It is clear a natural avalanche cycle was occurring yesterday, we are just not sure of the extent yet.

Fresh avalanche debris in the 5 Sisters slide path in Portage Valley. This path sits next to the 5 Fingers ice climbs. 12.26.22.

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • 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.

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

The first storm in a series of storms is slowing down this morning. Light rain is expected up to 1,000′ with light snowfall above this. Ridgetop winds will continue from the east but have backed off to the 20-30mph range. Despite the slowing of the storm, avalanche danger remains HIGH. Road conditions could also remain dangerous. I attempted to drive to Turnagain Pass yesterday and was turned around due to incredibly slick roads.

How the snowpack is responding to the onslaught of rain, warm snow, and wind is pretty clear from debris in the few avalanche paths seen along the Seward Highway. Today, natural avalanche activity should slow down but probably won’t entirely stop until cooler temperatures settle in and winds become light. We can expect all the varieties of storm avalanches: wet loose avalanches due to rain on snow below 2,000′, wind slabs releasing on wind loaded slopes in the higher elevations, storm slabs releasing in the weak older snow that the new snow is falling on, and dry snow sluffs in steep terrain.

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

Hopefully we can get some breaks in cloud cover to assess the extent of the recent avalanche activity. We are especially interested to see if avalanches are breaking deeper in the snowpack, in faceted snow around the old Thanksgiving crust. This would create a larger avalanche that could propagate wider than your typical wind slab or storm slab. As we move forward in time, understanding if these old weak layers could be triggered by people will be one of our biggest questions. For now however, avoiding avalanche terrain and letting the mountains do their thing is recommended.

Weather
Tue, December 27th, 2022

Yesterday:  Warm, wet, and windy… Moderate to heavy rain fell to 2,000′, possibly higher yesterday with heavy snowfall above this (.5 to 2″ of water in the past 24-hours, equating to 5-20″ of snowfall up high). Ridgetop east winds were 25-45mph with gusts near 70mph. Temperatures hovered near 35F from 2,000′ and below and were near 25-30F along the peaks.

Today:  The stormy weather should continue through today although precipitation rates and winds will be less than yesterday. Between .25 and .5″ of rain is expected at 1,000′ and below while 3-5″ of snow should fall at the high elevations. Ridgetop winds look to be 15-25mph with gusts near 40mph from and easterly direction. Temperatures will slowly decrease through the the day (mid 30’s at sea level and ~32F at 2,000′).

Tomorrow:  The active storm pattern should remain tomorrow with light precipitation, strong ridgetop easterly winds, and cooling temperatures. The rain/snow line could drop to close to sea level by tomorrow morning. Stronger pulses of moisture look to hit Friday and into the New Year.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35 rain 0.3 41
Summit Lake (1400′) 35 rain 0.1 28
Alyeska Mid (1700′) 35 rain 0.7 38
Bear Valley – Portage (132′) 40 rain 2

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 NE 35 69
Seattle Ridge (2400′) 29 SE 12 24
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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.