Thu, December 27, 2012 Turnagain Pass Avalanche Forecast

Thu, December 27th, 2012

Alpine
Above 2,500'

High (4)

Treeline
1,000'-2,500'

High (4)

Below Treeline
Below 1,000'

High (4)

Alpine Above 2,500'		High (4)
Treeline 1,000'-2,500'		High (4)
Below Treeline Below 1,000'		High (4)

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

New storm snow proves to be a valid concern today after several observations this week of human triggered avalanches and some downright spooky test results from our snow pits yesterday, all from below tree line. As we have watched our seasonal snowpack more than double in a few short days, the weak layers we’ve been talking about for the last month finally have a 2-5 foot slab sitting on top of them. This is the piece of the avalanche puzzle that has been missing until this week! The new slab sits on several different weak layers, any of which may fail with the weight of a person causing an avalanche that will prove unmanageable in steep terrain. We are in a direct-action avalanche situation and triggering an avalanche should be of no surprise today based on what we know about our weak foundation and overlying storm slab. The old mantra to stay out of the mountains for at least 24 hours during and after a storm rings loud and true this week!

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

Easterly winds looked to have picked up overnight with the approach of this latest low-pressure system. Even though we have limited data from upper elevations (due to poor visibility and dangerous avalanche conditions) we can safely say that tender wind slabs are forming and most likely avalanching naturally in our core advisory area. Human triggered avalanches will be very likely in terrain above tree line today. AKRR and DOT crews were able to affect wind slabs with artillery above Turnagain arm yesterday. Shots were yielding consistent results producing avalanches big enough to destroy a small building or break trees. We can expect wind slabs to continue to build today in our upper elevations. If these don’t avalanche naturally, only time will help to heal these slabs.

Weather

Thu, December 27th, 2012

Well the snow continues to pile up this week as the pattern change we were all hoping for did not disappoint! Turnagain pass saw an additional 8-10 € of snow yesterday, turning to a rain-snow mix at 1000′ overnight. Winds looked to have peaked from the east in the low 80’s last night.

Today looks to be more of the same with another 3-6 € of snow expected and moderate winds from the east. The rain/ snow line will be hovering somewhere between sea level and 1000 feet as this latest low begins to dissipate today.

Looking out toward the weekend there appears to be more unsettled weather in our future!

Total snow accumulation beginning early morning on the 24^th:

Girdwood Valley €“ ~50 € snow with 5 € of water equivalent
Turnagain Pass €“ ~45 € snow with 4.3 € of water equivalent
Summit lake €“ ~12 € snow with 1.1 € water equivalent

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

Fitz will issue the next advisory Friday morning December 28th.

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.