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 9th, 2022 - 7:00AM
Expires
Sat, December 10th, 2022 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE today for elevations above 1000′. Strong northwest winds are building sensitive wind slabs, making natural avalanches around 2′ deep possible and human-triggered avalanches likely. Today’s dangerous avalanches conditions will require cautious route finding. The most likely places to run into trouble will be just below ridgelines, in steep gullies, or on convex rolls.

The danger is MODERATE below 1000′. The winds will have less impact at our lower elevations, but it will still be possible to find reactive wind slabs. There is also a chance of avalanches failing in higher elevations and running down below treeline.

PORTAGE, SUMMIT, SEWARD: All of our periphery zones are expected to see the same, if not stronger winds than the core advisory area. This increases the likelihood of natural and human-triggered avalanches.

Special Announcements

Chugach State Park: The front range received up to 2′ or more of new snow on Tuesday/Wednesday, and have seen strong winds since. This is a big load of new snow on top of a thin and weak snowpack. Dangerous avalanche conditions exist, especially in areas being impacted by the moderate to strong NW winds.

Motorized Areas: All motorized areas remain closed. The recent storm favored the Anchorage area and we still need a deeper base at the trailhead elevations for the forest to open for motorized travel. Stand by to see how the next storm system on Sunday/Monday plays out!

Forecaster Chat #1: Come join forecaster John Sykes at Alaska Mountaineering and Hiking from 7-8 pm on December 15th to discuss current conditions, how to submit quick and quality observations, and decision-making during complex snowpack conditions. Admission is free and all are welcome!

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Fri, December 9th, 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

Yesterday we saw multiple small to large natural avalanches near the south end of Turnagain Pass (more info here). Most of these were partially filled in by new and blowing snow, but look to have occurred during the tail end or immediately after the Tuesday/Wednesday storm. Most of this activity was on terrain that had been wind-loaded, and they looked like they only involved new snow. The larger ones were big enough to bury a person.

Natural wind slab avalanche on the front side of Seattle Ridge, just up from the Bertha Creek parking campground near the south end of the ridge. Photo: Peter Wadsworth. 12.08.2022

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

The northwest winds are going to pick up today before dying down later tonight, and it’s looking like they are going to get strong enough to impact more of Turnagain Pass. Weather stations have been showing sustained speeds around 10-15 mph with gusts of 25-30 mph at Turnagain Pass– including the Sunburst station, which tends to be sheltered from these northwest winds. Our core forecast zone has been relatively protected for the past few days, with speeds around 25-40 mph for most of the day in Summit yesterday, and the AKRR mile 43 station showing gusts as high as 97 mph yesterday morning. We are expecting to see sustained speeds around 20-30 mph in the Turnagain Pass area today. Long story short, it is likely we will be able to find reactive wind slabs today, especially in the mid and upper elevations.

These fresh wind slabs are forming on top of a layer of facets in a lot of terrain, which will make them especially sensitive initially, and will most likely keep them reactive a little longer than your typical wind slab. The best way to stay out of trouble today is by avoiding wind-loaded terrain. The most dangerous slopes will be just below ridgelines, in steep gullies, and on convex rollovers. These northwest winds tend to load terrain differently than our more common easterly winds, so be on the lookout for fresh wind slabs in unusual areas. You should be able to find generally safer conditions (and higher quality snow) in terrain that has been sheltered from the winds.

If these outflow winds end up missing Turnagain Pass again, conditions won’t be quite as dangerous. You should be able to assess winds from a distance by looking for plumes of snow blowing off ridgelines. It is easy to identify wind slabs up close as you travel by stepping off the skin track and feeling for dense, stiff snow on top of softer snow. You can also use small test slopes to see how the new snow is behaving. Just be sure to use slopes that couldn’t produce an avalanche big enough to bury or injure someone.

Checking out a recent avalanche on the north side of Cornbiscuit. This avalanche was fairly small, but there was enough debris piled up in the gully below it to easily bury a person. Photo: Peter Wadsworth. 12.08.2022

Click Here to view the video below if it doesn’t load in your browser.

Weather
Fri, December 9th, 2022

Yesterday: Skies were mostly sunny, with temperatures slowly dropping from the mid 20’s to the mid teens F. There were strong northwest winds around much of the larger area, but Turnagain Pass and Girdwood stayed relatively calm, with sustained speeds of 5-15 mph and gusts of 25-30 mph. Compare this to the Mile 43 weather station, which had sustained speeds of 25-45 mph and gusts as high as 97 mph.

Today: Winds are expected to increase today for our core forecast area, with sustained speeds of 20-30 mph and gusts of 30-50 mph. Winds should be strongest later this morning, but are expected to continue through the day before calming down later tonight. Temperatures will continue their slow decline today, with highs in the single digits to low teens F, dropping to the single digits above and below 0 F tonight. Skies will be mostly sunny and no precipitation is expected.

Tomorrow: Things begin to change once again tomorrow. Cloud cover will increase as winds shift back to the southeast at 5-10 mph. High temperatures will be in the single digits to mid teens F, and no precipitation is expected during the day. It is looking like a proper storm is on the way for Sunday and Monday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 17 0 0 30
Summit Lake (1400′) 18 0 0 21
Alyeska Mid (1700′) 17 0 0 29
Bear Valley (132′) 25 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 7 WNW 10 30
Seattle Ridge (2400′) 14 NW 10 25
Observations
Recent Observations for Turnagain Pass
Date Region Location
02/08/23 Turnagain Observation: Eddie’s
02/07/23 Turnagain Observation: Seattle Ridge
02/07/23 Turnagain Avalanche: Pete’s North
02/06/23 Other Regions Observation: Johnson Pass to Bench Lake
02/05/23 Turnagain Observation: Rookie Hill
01/31/23 Turnagain Observation: Johnson Pass area
01/29/23 Turnagain Observation: Tincan Backdoor
01/28/23 Turnagain Observation: Sunburst
01/28/23 Turnagain Avalanche: Seattle Ridge
01/28/23 Turnagain Observation: Tincan Common
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.