Thu, February 18, 2016 Turnagain Pass Avalanche Forecast

Thu, February 18th, 2016

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		Moderate (2)
Treeline 1,000'-2,500'		Moderate (2)
Below Treeline Below 1,000'		No Rating (0)

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

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

Yesterday wind loading was observed in Turnagain Pass with Northeast ridgetop winds blowing 15-25 mph for most of the day. These fresh slabs could be tender and may awaken older deeper wind slabs (1-3’ thick) that formed over Valentine’s Day weekend. Be aware of this problem on slopes steeper than 35°, especially near rocks and on unsupported terrain features. Over the last few days observations have shown good bonding since Monday when two separate human triggered avalanches occurred in the Goldpan area of Turnagain Pass. Avalanching has not been widespread, but this set-up needs to be considered, especially later in the day with increased sun exposure.

Loose snow avalanches: There is the potential for wet loose avalanches on steep southerly slopes and dry loose avalanches on steep northerly slopes. Remember these will release at your feet but may gain momentum and catch you from behind as you travel downhill. Evaluate terrain where taking a fall could have high consequences.

Two small (D1) avalanches on ‘Juniors’ West aspect of Seatte Ridge, apear to be skier triggered. No official report of timing of these avalanches, but likely occured on Monday.

Avalanche Problem 2

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

Cornices have released naturally over the last few days and many have triggered fresh wind slabs. When approaching a ridgeline it can be challenging to recognize a safe distance. Be very skeptical of other tracks along ridgetops and don’t be tempted to walk to the edge for a better look. Cornices are notorious for breaking much further back than expected and if one releases it will be very large. Natural cornice fall activity should also be anticipated with warming from the sun, thus avoid spending time below cornices.

A massive cornice feature above ‘Mamma’s Bowl’ on Seattle Ridge at the very top of the up-track.

Additional Concern

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

Glide Cracks cover many steep slopes between 1000’ to 2500’ and continue to release without warming. Over the last few days several have released and many have significantly widened. Be extra diligent about planning your route to avoid these unpredictable hazards. Minimize any time directly underneath and do not re-group below them.

A very large glide crack above a common “re-group” area in Main Bowl in Seattle Creek.

Weather

Thu, February 18th, 2016

Yesterday was partly sunny becoming mostly cloudy by mid afternoon. Temperatures warmed to the mid 30’s F along the highway, but remained cooler, low 20’s F at higher elevations. Moderate Northeast winds 15-25mph blew all day and just started subsiding this morning.

Partly sunny skies are anticipated again today with Easterly ridgetop wind decreasing to 10-15mph. Day time temperatures with sun exposure may reach the mid 30’s F again today, but shaded area will likely remain in the 20’sF.

A similar pattern is expected tonight into tomorrow, but with increased cloud cover.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	28	0	0	102
Summit Lake (1400′)	24	0	0	30
Alyeska Mid (1700′)	27	0	0	86

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	ENE	12	35
Seattle Ridge (2400′)	22	~	~	~

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 Sat, September 23rd, 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	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Placer River	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Skookum Drainage	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Turnagain Pass	Closed	Scheduled opening on the Wednesday before Thanksgiving per Chugach National Forest plan. Subject to adequate snow cover.
Twentymile	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Seward District
Carter Lake	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Lost Lake Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Primrose Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Resurrection Pass Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Snug Harbor	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
South Fork Snow River Corridor	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Summit Lake	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.