Wed, December 18, 2013 Turnagain Pass Avalanche Forecast

Wed, December 18th, 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

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

Storm snow from Dec. 13/14^th continued its settling process as relatively warmer temperatures (above 0 F) today will promote bonding, allowing more of a consistent or interconnected slab across a given slope. It is unclear still if warmer temps today will do much to affix last weekend’s storm snow to our December drizzle crust from 12/7. We have had several reports of small, skier triggered soft slabs running on this crust over the last few days.

The crust is easy to find as it proves supportable to a skier and is widespread throughout the Turnagain zone. Given time it will continue to break down and become absorbed into our mid-winter snowpack but right now we are paying particular attention to how any new load of snow will react on this bed surface. Continue to pay attention to steeper, rocky terrain or convex rollovers where you may pull out a soft slab pocket today.

Moreover let’s not lose site of what lies below. The lower half of our snowpack consists of very weak, faceted snow. I suspect a big enough trigger such as a snowmachine may be able to penetrate this rotten layer and produce an avalanche.

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

Our surface still consists of low density, loose snow that is ripe for wind transport with the coming storm (see mountain weather below). New surface hoar has also formed over the last couple of cold and clear nights to cap our snowpack. If winds pick up early enough in the day today, we could see wind slabs forming below ridges and on cross-loaded slopes prior to nightfall.

Weather

Wed, December 18th, 2013

Yesterday temperatures were stubborn to break single digits. Winds were generally light form the north and northwest allowing valley fog to stay in place for much of the day in low lying areas while anyone in the upper elevations was rewarded with clear skies and a very low (on the horizon) sun.

Expect today to be a day of transition as mid and high level clouds move in to our area ushering in the arrival of what looks to be a quick, yet potent blast of winter weather. A strengthening low-pressure system to our south will arrive this afternoon/ evening packing SE winds and ample snow. There is a Blizzard Warning in effect for 6PM this evening. The peak intensity of this storm looks to hit the eastern Turnagain Arm region overnight and if the system lines up favorably, we could wake up tomorrow with 12-18 € of new snow. The exact track of this low will play a big role in wind direction and specifically what areas are favored with snowfall, but in short precip will be in the form of snow across our region and winds will be moderate to strong overnight, creating those blizzard conditions.

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.