Tue, January 05, 2021 Turnagain Pass Avalanche Forecast

Tue, January 5th, 2021

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Low (1)

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

Yesterday the forecast wind and snow did not materialize. However, winds on Sunday and Sunday night were strong enough to blow the light surface snow around and winds may be gusty at times today at upper elevations. Winds have already bumped up a bit this morning. Today it will be important to watch for blowing snow and wind slabs in steep wind exposed terrain near ridgetops, on convex rollovers, or in cross-loaded gullies. Look for stiff wind affected snow and cracking in the snow around you. Even a small wind slab triggered in high consequence zones can be quite dangerous if you get knocked off your feet. As always, keep a close eye on the surface conditions and know your escape routes if a small slab happens to break under you.

Cornices: Give cornices plenty of room and limit your time traveling below them.

Sluffs: Be aware of loose snow avalanches moving in steeper terrain wherever there is soft snow at the surface. With enough volume these can pick up momentum, enough to carry a person, and can be particularly dangerous if you are caught above terrain traps like cliffs, rocks, or gullies.

Small wind slab on the apron of a couloir in the Library. 1.3.21. Photo: A Meyerhofer.

Active flagging on Kickstep ridge around 3500’ and to the summit on Sunday, 1.3.21. Photo: Emily Sullivan

Additional Concern

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 December 1st rain crust/facet combination that we have been discussing as a layer of concern has become a layer to track at this point. The snowpack has had time to adjust to last major loading event and this layering structure and facet development is quite variable across the forecast area. Triggering an avalanche on this crust/facet layer is unlikely. However, we will continue to evaluate the progression of faceting above and below the December 1st rain crust as well as any future failure/avalanche potential. This type of set-up has a nasty habit of waking up from dormancy with additional loading, even if it is deep in the snowpack.

Glide avalanches: On a completely different note we have another additional concern to track. Glide cracks have been observed in Summit Lake on Gilpatrick and in Turnagain Pass on Seattle Ridge. Watch for additional cracks appearing in the region and remember to limit time spent underneath glide cracks as they are totally unpredictable and can release without warning.

Glide cracks on Seattle Ridge north of the uptrack. 1.3.21. Photo: Rachel Heath.

Weather

Tue, January 5th, 2021

Yesterday: Skies were cloudy with very light snow showers and a trace of accumulation. Temperatures were in the 20°Fs and winds were easterly 5-15 mph with gusts into the 20s. Overnight skies remained cloudy with a continued very light dusting of snow, temperatures remained in the 20°Fs and winds were easterly 5-10 mph with gusts into the high teens.

Today: Mostly cloudy skies becoming partly cloudy in the afternoon and a chance of scattered snow showers. Winds will be easterly 5-15 mph with gusts into the 20s and 30s and temperatures will be in the 20°Fs. Tonight skies will be partly cloudy becoming mostly cloudy with snow showers likely early Wednesday morning. Temperatures will remain in the 20°Fs and easterly winds continue, 5-15 mph with gusts into the 20s increasing in the early morning hours on Wednesday.

Tomorrow: Snow and rain showers are likely as the temperatures rise into the 30°Fs at sea level and high 20°Fs at upper elevations as the next storm moves into the region with some warmer air. Easterly winds will increase to 15-25 mph with gusts into the 40s. Rain and snow with some periods of heavy precipitation and elevated winds are forecast through Thursday.

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

	Temp Avg (F)	Snow (in)	Snow Depth (in)
Center Ridge (1880′)	27	trace	74
Summit Lake (1400′)	25	trace	30
Alyeska Mid (1700′)	26	trace	78

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	E	9	27
Seattle Ridge (2400′)	23	E	4	15

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.