Mon, February 18, 2013 Turnagain Pass Avalanche Forecast

Mon, February 18th, 2013

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

Low (1)

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

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

Loose Snow Avalanches

New snow in the past 24 hours fell in many places without any associated winds. Up to a foot of new snow can be found in the upper elevations with half that amount in the lower elevations. This snow is “right side up”, as temperatures overnight have gradually cooled. Loose snow avalanches will be a concern on steep upper elevation slopes today. Periods of sunshine will increase the likelihood of triggering these slides. These avalanches have the potential to knock people off of their feet or snowmachines. As such it will be best to avoid steep slopes above terrain traps where sloughing could pull people into gullies, over cliff bands and into trees.

Wind Slabs
In the upper elevations isolated pockets of older wind slab may be triggered by a skier or rider today. These pockets will be harder to detect, as a blanket of lighter density new snow sits on top of these slabs. Staying off of steep previously wind loaded terrain features will help in avoiding this problem today.
With light to moderate winds forecasted for today, expect to see shallow new wind slabs forming near ridgetops through the day. With ample light density snow available for transport, expect these slabs to form easily and be most sensitive as they are forming.

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 mid elevations (between 1,500-2,800′) have a snowpack structure that has some potential to produce larger more dangerous avalanches. A crust formed in late January has a very thin layer of weak snow above it in many areas. Above that weak layer are slabs ranging in depth from 1-3 feet. We have been investigating the likelihood of triggering an avalanche on this interface and have found mixed results within our forecast zone. In some areas snowpit tests have shown this layer to be reactive and in other areas it has been a non issue. While we’ve only had one report of a human triggered avalanche on this layer in the last week, the potential still exists. The best way to avoid this problem is by managing your terrain and staying away from potential trigger points (e.g., steep rollovers, areas of thin snow) within this elevation band.

Weather

Mon, February 18th, 2013

Snowfall that began in the early morning hours on Sunday have accumulated up to a foot of new snow in the higher elevations. Water amounts across the area range from .75″ in the Girdwood Valley, .5″ on Turnagain Pass and .3″ at Summit Lake. Winds have been very calm out of the North. Temperatures have been on a steady decline this morning with ridgetop stations reporting an average of 10 degrees F.

Today we should expect to see snow showers tapering off in the morning giving way to clear skies by this afternoon as a brief pause between storms takes hold. This break will be short lived, as the next low pressure system moves into the area from the Southwest by tomorrow afternoon.

______________________________________________

Wendy will issue the next advisory tomorrow morning, February 19th.

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.