Tue, February 12, 2013 Turnagain Pass Avalanche Forecast

Tue, February 12th, 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

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

It will be unlikely that we’ll see any natural avalanches today though it will be possible for a skier or snowmachiner to trigger a wind slab formed during our last storm day (Saturday). Pay attention to any red flags (recent avalanches, shooting cracks or collapsing in the snowpack) and continue to avoid cross-loaded gullies or steep wind-loaded terrain below ridges, as these are likely areas to trigger a wind slab. Stability tests from yesterday gave us some confidence in the Turnagain pass area that the new storm snow from over the weekend is bonding well to the older snow surface.

However, in areas such as the Girdwood Valley that received significantly more snow than Turnagain this past weekend, wind slabs will be deeper and easier to trigger. A report of a class 3 avalanche yesterday in the Girdwood valley showed significant propagation, likely on facets forming near a crust around 2700’.

One can sluice out several of these different crusts (rain, rime and melt-freeze) in our mid to upper pack with a hasty snow pit or probe poke. These distinct layers can act as a good bed surface or interface that a relatively shallow avalanche may step down to. Crusts are widespread throughout the forecast area, proving reactive in the mid elevation band at and just above treeline.

CNFAIC forecaster John Fitzgerald “feeling out the crusts” (~2600’) in addition to measuring spatial variability (depth) across a slope.

Avalanche Problem 2

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

Loose, low-density surface snow will not be gaining any strength today as temps stay cool. Sluffs initiated in steep terrain greater than 35 degrees will have the tendency to run fast and far. Expect it, manage your terrain accordingly (avoiding terrain traps) and this should not prove a significant issue.

Cornice fall also warrants a brief discussion as we did find evidence of cornice failure on Seattle ridge yesterday. Cornices have a very nasty habit of breaking farther back than you expect so it’s a good idea to travel well away from the face of a cornice as these monsters continue to ripen into mid-February.

Weather

Tue, February 12th, 2013

Snow tapered off quickly yesterday morning giving way to mostly clear skies, calm winds and dropping temperatures.

2-5 € of snow and southeast winds in the 10-20 mph range are expected today under cloudy skies. Temperatures have rebounded somewhat this morning from a low of 16 degrees at 1800′ yesterday and look to land in the comfortable range of the high 20’s at 1000′ today. Snowfall is expected to become heavier this evening and overnight as a series of weak surface lows are lining up this week, keeping the weather active in south central Alaska for the near-term.

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Kevin will issue the next advisory tomorrow morning February 13th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
01/29/23	Turnagain	Observation: Tincan Backdoor	AAS-Level 1 1/27-1/30
01/28/23	Turnagain	Observation: Sunburst	Brooke Edwards
01/28/23	Turnagain	Avalanche: Seattle Ridge	W Wagner
01/28/23	Turnagain	Observation: Tincan Common	Tony Naciuk
01/27/23	Turnagain	Observation: Sunburst	John Sykes
01/27/23	Turnagain	Avalanche: Lynx Creek	Megan Guinn / W Wagner
01/25/23	Turnagain	Observation: Cornbiscuit	John Sykes Forecaster
01/22/23	Turnagain	Avalanche: Tincan	Schauer/ Guinn
01/21/23	Turnagain	Avalanche: Seattle Ridge	Elias Holt
01/21/23	Turnagain	Avalanche: Lynx drainage – avalanche	CNFAIC Staff

Riding Areas

Updated Fri, January 06th, 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	Open	Opened Dec 13th.
Placer River	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Skookum Drainage	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Turnagain Pass	Open	Opened Dec 13th.
Twentymile	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Seward District
Carter Lake	Open	Opened Dec 13th.
Lost Lake Trail	Open	Opened Dec 13th.
Primrose Trail	Open	Opened Dec 13th.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Open	Opened Dec 13th.
South Fork Snow River Corridor	Open	Opened Dec 13th.
Summit Lake	Open	Opened Dec 13th.