Wed, February 20, 2013 Turnagain Pass Avalanche Forecast

Wed, February 20th, 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

Storm Slabs

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.

More info at Avalanche.org

Storm snow combined with wind overnight with gusts to 70 mph will make dangerous avalanche conditions in higher elevation terrain. Today, as the snowfall continues to build, we can expect wind slabs 1-2 feet deep to be reactive to human triggers. It may be difficult to travel above treeline due to poor visibility…

Below treeline, a low to moderate danger exists today. Some areas in the trees that are more prone to wind loading may have shooting cracks and small reactive wind pillows. Larger runouts are worth avoiding today until the new snow has time to settle.

Avalanche Problem 2

Persistent Slabs

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.

More info at Avalanche.org

The persistent slab is the enigma that is keeping us on our toes. Despite the old age of these weak layers, they remain active on an infrequent basis. Two specific issues are at play right now –

1. A crust formed in late January is now 2-6 feet deep. There was a report of a slide, possibly on this layer in Junior’s bowl on Seattle ridge earlier this week. This layer seems to be a problem only at a focused elevation band between 1900 and 3000 feet, which is mid-elevation for most of our local mountains.

2. The old October/November facets that have been dormant for the past 6-8 weeks finally showed themselves at Carter lake on Monday. A snowmachine triggered avalanche slid to the ground on a south facing slope, narrowly missing people watching at the bottom and damaging a couple sleds that were parked. This problem is more likely to be found in the central portion of the Kenai peninsula where the snowpack is thinner and the deeper layers are more easily influenced by the weight of a person or snowmachine.

Weather

Wed, February 20th, 2013

The blizzard warning overnight seemed to bring more snow to Grandview than to Girdwood or Turnagain Pass. Snowfall is likely more than a foot in some areas over the last 24 hours, with an average closer to 8 inches. It is still snowing as of 7am this morning. Wind peaked around 5pm last night and gradually diminished. Gusts are still reaching into the 30s, which is ideal to move snow around and create wind slabs and cornices. Temperatures rose from the single digits yesterday morning to the mid to high 20s today.

3-6 inches snow is expected today, with continued moderate to high wind. Precipitation should remain as snow to sea level.

Graham will issue the next advisory on Thursday, February 21st.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/22/23	Turnagain	Avalanche: Tincan	Nick D'Alessio
05/12/23	Turnagain	Avalanche: Tincan, Sunburst, Magnum, Cornbiscuit	Heather Thamm
05/07/23	Turnagain	Observation: Tincan – Bear Tracks	CNFAIC Staff
05/05/23	Turnagain	Observation: Seattle Ridge	AS/ WW Forecaster
05/02/23	Turnagain	Observation: Cornbiscuit	Schauer/ Sturgess Forecaster
05/02/23	Turnagain	Observation: Seward Hwy Turnagain Pass	Joel Curtis
04/30/23	Turnagain	Observation: Magnum	Ayla, Kit Crosby, Barton
04/29/23	Turnagain	Observation: Tincan	John Sykes
04/28/23	Turnagain	Avalanche: Taylor Pass/Pastoral	Schauer/ Creighton Forecaster
04/28/23	Turnagain	Avalanche: Tincan	Andy Moderow

Riding Areas

Updated Thu, June 01st, 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	Closed	Closed May 15.
Placer River	Closed	Closed May 15.
Skookum Drainage	Closed	Will close to motorized use on April 1, 2023 per the National Forest Plan.
Turnagain Pass	Closed	Will close on June 1.
Twentymile	Closed	Scheduled closure May 1.
Seward District
Carter Lake	Closed	Scheduled closure May 1.
Lost Lake Trail	Closed	Scheduled closure May 1.
Primrose Trail	Closed	Scheduled closure May 1.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Closed	Extended opening until May 15.
South Fork Snow River Corridor	Closed	Scheduled closure May 1.
Summit Lake	Closed	Scheduled closure May 1.