Sat, January 19, 2013 Turnagain Pass Avalanche Forecast

Sat, January 19th, 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

Deep Persistent Slabs

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

More info at Avalanche.org

The primary concern today is still the deep slab, which is becoming more stable over time. We haven’t had reports of deep slab avalanches since Monday when the last storm system ended. The snowpack is showing evidence of strengthening, but a number of tests consistently still show a low probability of initiating a large avalanche.

This kind of deep slab problem needs to earn our trust. We have growing confidence, but only to a certain point. The consequences of causing a full depth avalanche still deserve our respect and some alteration in our terrain choices. Areas with thinner snow cover are more suspect, and steep rocky terrain may hold the trigger points that could activate a large avalanche.

Now that the deep weak layer has been dormant for a few days we can expect a low possibility of triggering it. A new significant snow load (which is in the weather forecast for tonight) will increase the chances of deep slab activity as additional stress gets added to the weak foundation (see picture below).

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

The small amount of snow predicted to fall this afternoon will build wind slabs at higher elevations. Based on the timing of this storm it looks like this problem will be minor today, but may build into a significant problem tomorrow.

Weather

Sat, January 19th, 2013

A blizzard watch is in effect for Girdwood, Seward, and Whittier starting this evening. It appears that this will not have a major effect on the daylight hours today, but it may cause a bump in the avalanche danger by tomorrow. We can expect increasing wind and up to 5 inches of snow by this evening.

If you are wondering how the mountains are doing for snow this year check out the graph below. Our snow depth is slightly above average, and the Snow Water Content measured at 1880 feet at Turnagain Pass (below) is just barely below average.

SWE

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/21/21	Turnagain	Observation: Sunburst	Schauer/ Behney Forecaster
04/19/21	Turnagain	Avalanche: Triangle, Seattle creek	Will Morrison
04/18/21	Turnagain	Avalanche: Turnagain Pass Road Obs	Andy Moderow
04/18/21	Turnagain	Observation: Seattle Ridge, approximately 300 yards south of the up track	Brent Byrne
04/17/21	Turnagain	Avalanche: Road obs	Johnston-Bloom / Moderow Forecaster
04/16/21	Turnagain	Avalanche: Seattle Ridge	Wendy Wagner Forecaster
04/16/21	Turnagain	Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge	CNFAIC Staff Forecaster
04/16/21	Turnagain	Observation: Sunburst	Lance breeding
04/15/21	Turnagain	Observation: Tincan	Schauer/ Rothman Forecaster
04/13/21	Turnagain	Observation: Turnagain Pass Road Obs	A Schauer Forecaster

Riding Areas

Updated Tue, April 20th, 2021

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	Open	No parking in turnaround at end of the road near the outhouse.
Placer River	Open	Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage	Closed	The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass	Open
Twentymile	Closed
Seward District
Carter Lake	Open
Lost Lake Trail	Open
Primrose Trail	Open
Resurrection Pass Trail	Closed	Closed for the 2020/21 winter season.
Snug Harbor	Open
South Fork Snow River Corridor	Open
Summit Lake	Open