Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 16th, 2021 - 7:00AM
Expires
Sun, January 17th, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 1,000′ due to another round of strong east wind with 6-10″ of new snow forecast today. Human triggered wind slab and storm slab avalanches are likely on slopes 35 degrees and steeper. Wind slabs, along with cornice falls, could release on their own. Wind slabs are expected to be in the 1-3′ range and touchy. The danger is MODERATE below 1,000′ where rain on snow will make human triggered wet loose snow avalanches possible. Cautious route-finding and conservative decision-making are essential again today.

SUMMIT LAKE: Only a couple inches of snow fell in Summit Lake yesterday morning and 2-3″ is expected today. This area has a much thinner and weaker snowpack. Any significant wind loading today could cause wind slabs to step-down into older layers.

LOST LAKE/SNUG: Little information is known regarding the snowpack and new snow amounts for the central Kenai Mtns and near Seward. Please use extra caution and let us know what you see by submitting a quick report HERE.

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Sat, January 16th, 2021
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

One avalanche was reported yesterday. It was in the Girdwood Valley (Notch Mtn) and was a skier triggered shallow 6″ thick soft slab that propagated on a rollover (photo below).

Shallow soft slab, skier triggered, in the Notch Mtn area of Girdwood Valley. Although too small to catch and bury a person, additional snowfall today may create a larger slab, big enough to cause grief. 1.15.21. Photo: Peter Symmes.

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

And the weather keeps coming. After 4-6″ of new snow fell yesterday morning, clouds parted and let the sun in for a several hours midday. This was a brief reprieve before clouds moved in last night ahead of today’s weather system. As of 6am this morning, another 3-6″ of new snow has fallen and ridgetop winds are blowing consistently in the 30-45mph range with stronger gusts. Today’s event should bring 6-10″ of snowfall by this evening and another few inches overnight tonight. Avalanches today should be associated with the new snow and winds. They’ll be in the form of wind slabs, storm slabs (where there is over 6″ of new snow), sluffs and cornice falls. At elevations below 1,000′ where it’s raining, wet sluffs are a concern.

The strong winds will not only be blowing the new snow into sensitive slabs, but the existing loose surface snow as well.  Wind slabs are likely to be in the 1-3′ thick range and even thicker just off ridgelines where it’s been blowing since midnight. Being that it’s storming today, areas with active wind loading should be easy to see and avoid. Be sure to stay out from under steep slopes that are getting loaded above you; for example under the steep face of Seattle Ridge pictured above. Watching for cracking in the snow around you and stiffer snow over softer snow is also a clue you’ve found a wind slab.

In areas out of the wind that see over 6″ of new snow, watch for storm slabs. These will be soft slabs as seen in the photo from Notch Mtn yesterday. They can propagate across the whole slope and even if they are only 6-10″ thick, can generate a good amount of debris in bigger terrain.

Cornices: With poor visibility, it’s unlikely a person will find themselves along a ridgeline, but one good way for a natural avalanche to occur is when a chunk of cornice breaks off. Cornices are growing with each storm and we’ve seen many of them start falling. Another good reason to avoid being under or on slopes with cornices above.

New 2020/21 CNFAIC forecaster Andrew Schauer takes a look at the snowpack on Sunburst yesterday. 1.15.21. Photo: Paul Wunnicke.

Weather
Sat, January 16th, 2021

Yesterday: Light snow showers in the morning were followed by clearing afternoon skies before clouds and snowfall pushed back early Saturday morning. Up to 5″ of low density snow was seen in Girdwood with a few inches on Turnagain Pass fell with the morning pulse and so far only a few inches has falling early this Saturday morning. Ridgetop winds were light and variable yesterday before ramping up overnight with the next system. Temperatures were near 30F at the mid elevations and the low 20’sF along the higher ridgetops.

Today: Moderate snowfall and strong winds are expected today as a quick hitting storm has moved in from PWS early this morning. Between 5-10″ of snow is forecast (~.7″ SWE) with a rain/snow line right around 1,000′. Ridgetop winds are averaging 35-45mph with gusts near 60mph from the east, where they are expected to remain through the day. Temperatures are rising and should peak midday in the mid-30’sF at 1,000′ and mid 20’sF along the high peaks.

Tomorrow: A brief break in storms is expected for Sunday before a more potent system arrives Sunday night through Monday. This event could bring an additional 2 feet of snow from 1000′ and above with strong easterly winds (expected rain/snow line between 500-1000′). A High Wind Watch has been issued by the National Weather Service for this storm.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 3 0.3 124
Summit Lake (1400′) 25 1 0.1 41
Alyeska Mid (1700′) 29 6 0.6 115

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22 NE 25* 57
Seattle Ridge (2400′) 26 SE 15* 33

*Estimated hourly wind average. Sunburst and Seattle Ridge anemometers have rime on them and were not reporting yesterday.

Observations
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Date Region Location
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04/23/21 Turnagain Avalanche: Sunburst
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04/22/21 Turnagain Observation: Turnagain Seattle Ridge / Seattle Creek
Riding Areas
Updated Sat, May 01st, 2021

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
North end of Johnson Pass Trail is open into May as conditions warrant.
Placer River
Closed
It is packrafting and jetboat season!
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Open into May as conditions warrant.
Twentymile
Closed
It is packrafting and jetboat season!
Seward District
Carter Lake
Closed
Closes May 1.
Lost Lake Trail
Closed
Closes May 1.
Primrose Trail
Closed
Closes May 1.
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
Open into May as conditions warrant.
South Fork Snow River Corridor
Closed
Closes May 1.
Summit Lake
Closed
Closes May 1.

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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.