Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, December 3rd, 2022 - 7:00AM
Expires
Sun, December 4th, 2022 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 2500′. A layer of sugary facets on the ground at upper elevations could produce avalanches 2-4′ deep, but the chances are decreasing since we have had no significant snowfall this week. Lingering wind slabs up to 1′ deep and dry loose avalanches (aka sluffs) are also possible in steeper terrain. Below 2500′ the avalanche danger is LOW.

Special Announcements

Forecaster Chat #1: Come join us at Alaska Mountaineering and Hiking on Thursday, December 15th for our first forecaster chat with John Sykes. Admission is free! Start time roughly 7pm, exact time TBD. The forecaster chat will focus on how to streamline submitting high quality observations and a discussion on decision-making in unusual conditions.

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Sat, December 3rd, 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

We saw a few small natural wind slabs yesterday on Magnum that probably released during the last wind event on 12.1.22. Otherwise the last observed avalanche activity were small natural wind slabs last weekend during the 11.25-26 outflow wind event.

Avalanche Problem 1
  • 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

The last known avalanche activity on the facet layer on the ground was back on 11.13.22, nearly three weeks ago. We are keeping it in the forecast due to uncertainty about the distribution and sensitivity of this layer at higher elevations. Our recent snowpit tests have shown a mixture of results, with some areas producing full propagation on this layer and other areas having no results. This is pretty typical for a deeply buried persistent weak layer. While we think it is unlikely for a person to trigger an avalanche 2-4′ deep on this layer today, we are still looking for more information from higher elevations (above 3000′) so please submit an observation if you get a chance to test this layer today!

There is also a possibility of finding a lingering wind slab up to 1′ deep today. The most recent round of wind slabs formed on 12.1.22 on top of a layer of near surface facets which can help them stay reactive longer than normal. These are most likely to be found in steep terrain along upper elevation ridgelines and cross loaded gullies. Keep an eye out for firm hollow feeling snow and shooting cracks to identify areas that could be holding onto a stubborn wind slab.

Finally, the clear skies this week have lead to faceting on the surface in areas protected from the wind which can lead to fast running loose snow avalanches (aka sluffs). If you are travelling in steeper terrain today be aware of your sluff because they can easily knock you off balance. We recommend always using safe travel practices to limit the exposure of your group to avalanche terrain. Travelling one at a time, spacing out, and always spotting your partners are critical to manage your avalanche risk even when it has been awhile since a recent snowfall event.

Mixture of soft snow and wind hardened snow in alpine elevations. Photo 12.2.22

Weather
Sat, December 3rd, 2022

Yesterday: A strong inversion was in place yesterday, with temperatures remaining in the single digits at the road elevation and reaching up to the low 30s at upper elevations. Winds were light, averaging 5-10 mph with gusts into the teens at upper elevations. High clouds moved into the area but the sun still shined through.

Today: Temperatures are getting downright balmy at upper elevations, as of 4am Sunburst weather station is reporting 35 F and Portage is reporting 2 F. That is one strong inversion! Temperatures at lower and mid elevations are expected to increase slightly later this afternoon, but the inversion should remain in place through the weekend. Winds will remain light with averages of 0-10 mph today. Some high level cloud cover is expected in the area today.

Tomorrow: Sunday looks like a repeat of Saturday except with clearer skies. A storm should to move into the area on Monday and provide us with a little refresh of snowfall on Monday afternoon and evening.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21 0 0 22
Summit Lake (1400′) 9 0 0 15
Alyeska Mid (1700′) 21 0 0 20
Bear Valley (132′) 6 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 31 W 7 18
Seattle Ridge (2400′) 29 SW 2 7
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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.