Tue, December 31, 2013 Turnagain Pass Avalanche Forecast

Tue, December 31st, 2013

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

Low (1)

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

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

The weak snow that is buried 12-18” deep in our snowpack remains our primary concern. The likelihood for triggering a slab avalanche that breaks in this older weak snow has been decreasing the last several days but the possibility does remain.

We have a small shot of snow expected today (1-3” forecast) with moderate to strong wind. Slopes where the wind is depositing snow will add stress to these buried weak layers and increase the likelihood of triggering one of these old slabs. However, the ‘real’ snow and wind event is expected overnight tonight through tomorrow where a foot or more of new snow will have the potential to overload the weak layers. We could see large and unmanageable avalanches 2-3+’ deep by tomorrow if this storm does verify.

Below treeline the slab is losing its cohesion and the pack is unsupportable. Though there is some localized collapsing in the alders, triggering an avalanche is unlikely.

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 will start picking up through the day to the moderate range on the ridgelines with gale force winds expected for tonight. Though there is limited snow to transport at the moment, we do have 1-3” of snow forecast to fall before 6pm. Watch for wind drifts and shallow slabs to start forming through the day. These should be confined to above treeline slopes and exposed rollovers.

Weather

Tue, December 31st, 2013

We have had a mild past 24-hours with temperatures in the mid 20’s F above sea level, light easterly winds at ridge tops and overcast skies.

Today a change is in store as a large area of low pressure heads our way from the South. We should see East winds pick up by the afternoon to the 30-40mph range on the ridgelines with 70-80mph by late tonight. Temperatures should be around 20F above treeline and near 32 at sea level. Snow accumulation of 1-3 € is expected with a snow/rain mix at sea level.

By tomorrow evening we are looking a total snowfall of 12-16 € (possibly more). The models are saying around 1.5 € of water equivalent from this afternoon through Wednesday night. It does look like we could finally get a decent shot of snow.

Some December stats below:

We end 2013 with a SWE that is only 15% of average for December. We also made the podium with this December being the 3^rd driest since 1983. Numbers below are from the Turnagain Pass SNOTEL Station (1880′).

Top 5 lowest December SWE from 1983 till 2013:

1^st 1984 €“ 0.5 €
2^nd 2011 €“ 1.3 €
3^rd 2014 €“ 2.5 € (plus whatever might fall before midnight tonight)
4^th 1985 €“ 3.1 €
5^th 2009 €“ 4.2 €

Average December SWE is 16.2 €

Snow Depth:
Dec 31 2013, today, snow depth 22 €
Average for past 10 years is 64 € (Data only goes back to 2004)

*The above numbers were calculated with SNOTEL data from the NRCS.

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.