Fri, January 14, 2022 Turnagain Pass Avalanche Forecast

Fri, January 14th, 2022

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Considerable (3)
Below Treeline Below 1,000'		Moderate (2)

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Recent Avalanches

Seward Highway: Natural avalanches ran to the valley in multiple paths along the Seward Highway just south of Girdwood yesterday.

Avalanche Problem 1

Wind Slabs
Almost Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

Likelihood of Avalanches

Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches

Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word	Size (D scale)	Simple Descriptor
Small	1	Unlikely to bury a person
Large	2	Can bury a person
Very Large	3	Can destroy a house
Historic	4 & 5	Can destroy part or all of a village

More info at Avalanche.org

We are looking at another day of dangerous avalanche conditions as a strong storm system finishes this morning. Yesterday’s heavy snowfall brought another 1-2′ snow to the mountains around Girdwood and Turnagain Pass, with higher totals near Portage and Placer. The Turnagain Pass snotel site at Center Ridge recorded 0.1″ Snow water equivalent (SWE) per hour for 12 straight hours yesterday. This storm came on the heels of another system that brought heavy snowfall earlier this week, resulting in the following accumulation since Sunday night:

Turnagain Pass: 2.2″ SWE, 2-3′ snow above 1500′
Alyeska Mid: 3.4″ SWE, 3-4′ above 1500′
Summit Lake: 0.6″ SWE, 6-8″ snow

This snow came with strong easterly winds. The Sunburst weather station recorded winds of 40-60 mph yesterday, gusting to 93 mph and six consecutive hours of gusts from 80-90 mph. The winds have died down slightly this morning, but strong easterly winds are expected to continue at 20-30 mph with gusts of 35-50 mph for most of the day today. This makes large human-triggered avalanches likely.

It is most likely a person will trigger an avalanche on steep, wind loaded slopes at and above treeline. Wind slabs are expected to be in the neighborhood of 2-5′ deep or deeper, and have likely formed a bit further below ridgelines with the strong winds we have been recording. You can also expect to find reactive wind slabs on convex rolls and in steep gullies. Dangerous avalanche conditions mean it is important to choose your terrain wisely. Today this means avoiding traveling on or below steep slopes, and as always, keeping an eye on your partners.

Strong winds at the Sunburst station yesterday. Winds have died down a bit, but are expected to continue at 20-30 mph today with gusts at 35-50 mph.

Avalanche Problem 2

Persistent Slabs
Almost Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

Likelihood of Avalanches

Size of Avalanches

Signal Word	Size (D scale)	Simple Descriptor
Small	1	Unlikely to bury a person
Large	2	Can bury a person
Very Large	3	Can destroy a house
Historic	4 & 5	Can destroy part or all of a village

More info at Avalanche.org

The storm has built thick slabs on a variety of weak surfaces. The most problematic we have seen so far is a layer of facets that formed on top of the New Year’s crust during last week’s clear and cold weather, which is now buried 2-5′ deep or deeper. We have seen this layer showing poor stability in our test pits, and it was failing on small test slopes yesterday in the Tincan trees (more info here). This layer has seen significant loading this week, which increases the likelihood of triggering an avalanche on it. In addition to the wind-loading mentioned in problem 1 above, it may be possible to trigger a large avalanche on steep sheltered slopes, where the layer is 2-3′ deep. There is a higher level of uncertainty associated with these potentially very large avalanches, which gives one more reason to dial back terrain choices today, avoiding traveling on or below steep slopes.

Poor stability test results on a weak layer of facets buried 2-3′ deep in the mid elevations at Tincan yesterday. This layer was breaking on some test slopes nearby during the day. 01.13.2022

Weather

Fri, January 14th, 2022

Yesterday: Heavy snow brought 14-18″ to Turnagain Pass, 18-24″ to Girdwood, and 4-8″ to Summit Lake, with rain up to around 1000′. Strong easterly winds were blowing 40-60 mph with gusts of 80-90 mph at ridgetops. Temperatures remained in the upper 20’s to low 30’s F through last night.

Today: Snowfall is tapering off this morning, but another 1-4″ is possible in Girdwood, with up to 6″ in Portage and Placer. Easterly winds will be sustained at 20-30 mph with gusts of 30-50 mph. Mostly cloudy skies will start to break up in the afternoon, with some pockets of sun possible before the end of the day. Rain level is expected to drop back to 400′ as the snow passes.

Tomorrow: Low temperatures will get down to the low to mid 20’s F overnight, with highs tomorrow in the mid 20’s to low 30’s F. Light winds will stay down at 5-10 mph with variable direction, and light snow could bring 1-3″ to sea level. Skies will be mostly cloudy.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	32	12	1.2	85
Summit Lake (1400′)	30	3	0.2	28
Alyeska Mid (1700′)	31	14	1.2	N/A

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	ENE	40	93
Seattle Ridge (2400′)	25	SE	15	36

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 Mon, May 15th, 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	Open	Chugach NF staff will be assessing daily after May 15th. Please keep machines on the snow and avoid brown spots to keep this area open as long as possible.
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.