Sat, January 05, 2013 Turnagain Pass Avalanche Forecast

Sat, January 5th, 2013

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Moderate (2)
Below Treeline Below 1,000'		Moderate (2)

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

Recent avalanche activity is the most pertinent information we have available, and it’s telling us a compelling story right now. Yesterday we had a new avalanche on the north end of the motorized side of Turnagain Pass, with wide propagation on an east facing slope. Around 850 in the morning yesterday the large avalanche path between Portage lake and the Whittier tunnel entrance slid full width and full depth. On Wednesday a large avalanche was triggered on Tincan by a skier, then we got another foot of snow. If you haven’t watched the video by Alyeska ski patrol yet, it’s worth taking a few minutes to see their perspective of managing the same deep slab problem at the ski area.

Our weak layer is now buried 3-10 feet deep, depending on wind loading. It is difficult for a single person to affect something that deep, but if a collapse is initiated from a shallow trigger point the resulting avalanche is likely to be very large. A skier should be concerned about trigger points in steeper terrain, including near exposed rocks, sparse trees, or on the edge of a wind scoured ridge. Snowmachines cause a greater force on the snow and will be more likely to be a deep slab trigger. Slope angles above 35 degrees deserve extra caution and avoidance, and every aspect is affected.

Common tools to identify avalanche hazard with this deep slab problem are not likely to be effective. Don’t expect to see shooting cracks or hear whoomphing, because that weak layer is buried deeper than your ski pole. Test slopes will also not show an unstable character unless they break full depth, which is what we’re trying to avoid in the first place. Compression tests on isolated snow columns may indicate false stable results. All this information is superseded by evidence of natural avalanche activity and a weak layer which we know is not gaining strength quickly.

Avalanche Problem 2

Wind Slabs

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.

More info at Avalanche.org

Forecasted wind is enough to create fresh wind slabs. We have yet to notice a problem within the storm layers of the last 12 days, but that’s mainly because few people have ventured above 2500 feet. Wind slabs are a concern of their own, but combined with a deep slab step down potential they can be extra dangerous.

Weather

Sat, January 5th, 2013

Little to no precipitation in the last 24 hours and moderate wind has not added much to the avalanche problem. Today 2-6 inches of snow is expected with strong southeast wind at the ridges. Slightly colder temperatures are expected to keep the snow line down to sea level.

In the long term, a chance of snow is in the forecast every day for the next 4 days. We will stay in the active pattern into next week, but not as intense as we’ve seen recently.

Wendy will issue the next advisory on Sunday, January 6th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
12/08/22	Turnagain	Observation: Magnum: Super Bowl/PMS Bowl	Schauer/ Wadsworth Forecaster
12/07/22	Turnagain	Avalanche: Tincan	John Sykes
12/07/22	Turnagain	Observation: Eddies skintrack	Iris Neary
12/06/22	Turnagain	Observation: Seattle Ridge- Main Bowl	Schauer/ Creighton Forecaster
12/04/22	Turnagain	Observation: Silvertip	Schauer/ Cullen Forecaster
12/04/22	Turnagain	Observation: Kickstep Glacier	Moderow / Wadsworth
12/03/22	Turnagain	Observation: Seattle Ridge	AS/ AR/MS/ME Forecaster
12/03/22	Turnagain	Observation: Seattle Ridge	Kakiko Ramos-Leon
12/03/22	Turnagain	Observation: Superbowl	Peter Wadsworth
12/02/22	Turnagain	Avalanche: Magnum/Cornbiscuit	John Sykes Forecaster

Riding Areas

Updated Fri, December 09th, 2022

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	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Placer River	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Skookum Drainage	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Turnagain Pass	Closed	The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions are being monitored daily. 22” of snow exists at the parking lot. Another storm on Sunday/Monday 12/11 may just do it.
Twentymile	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Seward District
Carter Lake	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Lost Lake Trail	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Primrose Trail	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
South Fork Snow River Corridor	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.
Summit Lake	Closed	The Forest has issued a closure order due to inadequate snow cover for resource protection. Conditions will be monitored daily. Scheduled opening would have been Dec 1st.