Tue, April 23, 2013 Turnagain Pass Avalanche Forecast

Tue, April 23rd, 2013

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Moderate (2)
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

Wet Loose

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

More info at Avalanche.org

Yep, we are finally getting our warm April temperatures and a little rain and snow today. We only have a small amount of precipitation forecast but, the main concern is how the snowpack is reacting to the warm temperatures and cloud cover. Below treeline, watch for the top 6-12+” of snow to lose cohesion and be easily pushed down any slope over 35 degrees. Mainly wet loose avalanches will be possible to trigger but there is also a potential for wet slabs around a foot deep to pull out. It is best to steer clear of any slope with soft wet snow deeper than 6″. Additionally, buried crusts in many areas can provide great bed surfaces allowing any slide triggered to run further than expected.

As for the larger and more dangerous slides: Once the entire pack warms up to a balmy 32F (0C) we call it isothermal and it looses much of its stability. This is the primary contributor to the shed cycle. Right now the snowpack at 2,000′ is not quite warm enough (see image below). However, snow can change rapidly and with that the avalanche danger. You can keep tabs on the evolution of the snowpack HERE but also keep in mind this is only one point (2,000′ on Center Ridge) and the snowpack varies considerably with elevation and aspect.

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

Above treeline we can expect several inches of heavy snow today with moderate to strong east winds. The new snow is likely to stick rather well to the existing surface at the mid elevations but upper elevations should see dryer snow with more of a classic winter wind slab problem. Expect any fresh slab found at these upper elevations to be sensitive as they will be sitting on either crusts (wind or sun) or loose faceted snow.

Additional Concern

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 are likely to start peeling off any day now with our recent warm temperatures. They have the potential to trigger avalanches below, entrain large amounts of snow and run into valley bottoms. Again, with the springtime warm-up on the way, be very wary of traveling in drainage bottoms for the next several weeks.

Weather

Tue, April 23rd, 2013

Yesterday we had a brief return to the sunny skies that have characterized April to date. Temperatures were quite warm, around 30F on ridgetops and the upper 40’s at 1,000ft. Ridgetop winds during the past 24 hours averaged ~15mph with gusts to 35mph from the east. The last snowfall ended 13 days ago, April 9th. Overnight, cloud cover has moved in and temperatures have only dropped 5-10F – it’s feeling like spring finally.

Today a warm, wet and windy, but fast moving, system is moving through from the Gulf. We should see around 4-6″ of dense snow above treeline and .3″ of rain below treeline throughout the day (rain/snow line ~1,500ft). Temperatures look to rise back to 30F on ridgetops and the mid 40’s at 1,000ft. Winds will remain from the east in the 15-20mph range with gusts to ~40mph.

Wednesday we should see partly cloudy skies as the system moves out and we return to a dry, but warm, period for the remainder of the week.

Kevin will issue the next advisory Thursday morning, April 25th.

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.