Wed, April 01, 2015 Turnagain Pass Avalanche Forecast

Wed, April 1st, 2015

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

No Rating (0)

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

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

Yesterday partly sunny skies provided good windows of visibility in Turnagain Pass following a week-long storm that left 2-3’ of new snow. Beneath this snow is a mixed bag of old snow interfaces ranging from facets, buried surface hoar, wind harden snow, sun crust, and melt/freeze. Yesterday several large (D3) remotely triggered avalanches were reported, including one within our forecast zone in Seattle Creek. Several large natural avalanches were also seen in this area including the West Face of Pyramid.

Due to the spatial variation and the thickness of the slab (2-3’) obvious signs of instability like collapsing may not be present. This makes assessing the current stability complicated and snow pit data will not be representative of the entire snowpack. Steep terrain above 2500’ and Northern exposures shaded from the sun are suspect of the greatest instability. Caution should also be used on other aspects including sunny exposures.

Sadly this is not an April Fools joke. If an avalanche is triggered today the consequences will likely be high. Until this new snow has had more time to adjust to its new load, staying off of steep terrain, especially Northern aspects will be advised.

*Human Factor Note: If visibility is good today Northern aspects may have the most appeal due their protection from the sun and high quality snow. Don’t forget to watch your slope angles, travel one at time between islands of safety, and always have an escape zone.

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 deserve a lot of respect right now. They have grown substantially during the past week and though some of these have fallen on their own, many are looming. Warm temperatures and solar gain can increase the likelihood for failure. Minimizing time spent underneath them as well as giving them a wide berth on ridgelines is extremely important.

The photo below was taken yesterday on a Southwestern aspect on Tincan near Todd’s run. Notice a very small slab initiated due to a recent cornice failure.

Weather

Wed, April 1st, 2015

Yesterday skies were partly sunny with cloud cover obscuring visibility along ridgetops at times. Temperatures were warm, mid 40’s F near sea level and high 20’s F near ridgetops. Winds were light (5-15mph) from the Northeast along ridgetops. Isolated flurries produced a small amount of accumulation in the morning, but by mid afternoon the sun melted this new snow at lower elevations.

Today skies will be mostly cloudy, but the sun may make a brief appearance in the afternoon. Light snow showers are anticipated at higher elevations with up to an inch of accumulation. Temperatures will be similar to yesterday. Rain/snow line will be near 500′. Winds will be light to moderate out of the Northeast, 10-25mph.

Tomorrow looks to be similar; mostly cloudy with mild temperatures, and a chance of rain and snow showers. Winds will continue to be light to moderate from the Northeast.

*Wind direction data at Seattle Ridge is not accurate at this time.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	1	.1	59
Summit Lake (1400′)	34	1	.1	10
Alyeska Mid (1700′)	35	trace	.08	34

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	NE	6	19
Seattle Ridge (2400′)	28	*	10	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 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.