Thu, March 03, 2016 Turnagain Pass Avalanche Forecast

Thu, March 3rd, 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

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

Cornice fall may be one of the larger hazards today with sunshine acting to weaken these already tenuous bombs. Cornices right now are LARGE and UNPREDICTABLE– some bigger than semi-trucks and some with large cracks extending their full length. Yesterday melting snow and dripping water could be seen on cornice faces during the heat of the day along Magnum Ridge. Today the sun will continue to weaken cornices making human triggered (snowmachine or skier) and natural cornice fall more likely in the afternoon. Limiting time spent under these is key and giving them extra room along ridgelines will be necessary. Not only would it suck to trigger a cornice while on top of one, imagine what it would be like if people were also below it. Evaluate all ridgelines and slopes for potential cornice fall and be weary of existing skin tracks and up-routes. There are many areas where the “normal” route is in the line of fire.

Magnum Ridge Cornice – The estabilshed skin track is directly on top of 30-40′ cornice feature.

Same corniced ridge on Magnum. Note the long crack observed on February 18th before a 10 day storm added more weight and stress to this cornice. Photo by Amanda Goss.

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

Strong winds during a 10-day storm have created layers of wind-affected snow throughout Turnagain Pass. Observations over the last several days have been showing this problem to be stabilizing, however today’s warm temperatures and direct sun could be a catalyst for a human triggered wind slab. Triggering a wind slab is still possible on slopes steeper than 35 degrees especially on slopes with unsupported terrain features. Ease into steeper terrain with caution and avoid solar aspects if you find moist surface snow or see wet loose point releases in motion.

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 are moving and coming out of hiding after they were covered by wind and snow during the storm cycle. Although it has been several days since the last glide crack we know of released and avalanched, they are still on the move. Limiting time spent under cracks is crucial, as they will mow anything down in their path if one does release.

Very large glide crack on the SW shoulder of Cornbiscuit – view from the Seward Hwy. The entire SW face of Cornbiscuit has extensive glide cracks. Click HERE for more pictures from yesterday.

Weather

Thu, March 3rd, 2016

Yesterday skies were clear and sunny and temperatures reached mid-high 30’s F during the warmest part of the day, around 2pm. Calm winds switched directions mid day from an Easterly direction to a Westerly direction. Overnight skies remained clear and temperatures dropped into the teens to mid 20’s F.

Today Westerly winds are expected in increase slightly 10-15mph along ridgetops. Skies will remain sunny and day time temperatures are expected to spike mid day.

Tomorrow a pattern shift is expected with a possibility of scattered snow showers.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	27	0	0	140
Summit Lake (1400′)	22	0	0	42
Alyeska Mid (1700′)	28	0	0	105

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	28	NE becoming W	4	10
Seattle Ridge (2400′)	24	n/a	n/a	n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/28/22	Turnagain	Avalanche: Turnagain Pass – late May wet slab cycle	CNFAIC Staff
05/21/22	Turnagain	Avalanche: Magnum, Lipps and Tincan	CNFAIC Staff
05/17/22	Turnagain	Avalanche: Sunburst	CNFAIC Staff
05/17/22	Turnagain	Observation: Tincan Ridge	Joe Kurtak
05/11/22	Turnagain	Avalanche: Cornbiscuit and Magnum west faces	CNFAIC Staff Forecaster
05/07/22	Turnagain	Observation: Granddaddy	Kit Barton
04/29/22	Turnagain	Observation: Sunburst wx station	AS/ MM/ AM/ NH
04/28/22	Turnagain	Observation: More Turnagain Pass/Summit Lake wet slab activity	Alex Marienthal
04/27/22	Turnagain	Observation: Magnum	Sykes / Buttrick Forecaster
04/27/22	Turnagain	Observation: Girdwood/Summit/Turnagain Road obs	A S

Riding Areas

Updated Wed, June 01st, 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	Closed as of May 1 per Forest Plan.
Placer River	Closed	Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage	Closed	Closed as of April 1st per Forest Plan.
Turnagain Pass	Closed	Closed as of June 1st.
Twentymile	Closed	Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake	Closed	Closed as of May 1 per Forest Plan.
Lost Lake Trail	Closed	Closed as of May 1 per Forest Plan.
Primrose Trail	Closed	Closed as of May 1 per Forest Plan.
Resurrection Pass Trail	Closed	Closed as of May 1 per Forest Plan.
Snug Harbor	Closed	Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor	Closed	Closed as of May 1 per Forest Plan.
Summit Lake	Closed	Closed as of May 1 per Forest Plan.