Fri, January 22, 2021 Turnagain Pass Avalanche Forecast

Fri, January 22nd, 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

Light snow showers are over most of the forecast area this morning, however they should only account for a few inches before tapering off midday. It will again be the winds that are the main driver for avalanche issues. Easterly ridgetop winds climbed last night into the 30-35mph range for averages and a peak gust at Sunburst weather station of 57mph. They have quieted down somewhat this morning, but should continue to average near 20-30mph before ramping up again tonight as the next system heads in. With a few inches of new snow possible today and any existing snow available to move around, we can expect fresh wind slabs in addition to any lingering slabs from the past couple days.

Wind Slabs: If you’re headed out in hopes the skies break enough for travel above the trees, keep a lookout for any recent (or current) wind loading. Feel for hollow drum-like snow, stiff snow over softer snow and cracks that shoot out from your machine, board or skis. Wind slabs are likely to be near ridgelines, on steep rollovers and in cross-loaded gullies. They could be anywhere from a few inches to a couple feet thick pending on the slope you are on and how much wind it has seen.

Cornices: Be extra cautious of where you are in relation to cornices. This photo below (from Tuesday 1.19) shows the top of the Seattle Ridge motorized up-track with a huge cornice. It’s easy to ride or hike up familiar slopes and forget how close we might actually be to a cornice’s edge that has grown during this month’s stormy weather. Cornices like this exist all over the ridgelines right now and giving them more space than one might think is prudent.

Large cornice along Zero Bowl (Mamma’s Bowl) on Seattle Ridge. Photo taken a few days ago on Tuesday 1.19.21. Beau Gehler.

Additional Concern

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

Say it isn’t so… Glide avalanches have arrived for the 2021 season. The good news, we are only seeing them in areas not likely to be traveled, but that can all change in a heartbeat, as we know from years past. The photo below shows the glide cracks on the southeast shoulder of Goat Mtn that were releasing yesterday. Cracks also have been seen on the southern lower face of Raggedtop (Girdwood Valley), on the southern slope of Gilpatrick and south of Devil’s Pass trail (Summit Lake area on the Kenai).

Keep an eye out for these ‘brown frowns’, avoid travel under them, and please let us know if you see any!

Glide cracks and release on the shoulder of Goat Mtn seen from Girdwood. The crack to the right of the release avalanched shortly after this photo was taken yesterday afternoon. 1.21.21.

Weather

Fri, January 22nd, 2021

Yesterday: Overcast skies were over the region yesterday with a few flurries here and there. Ridgetop winds were east in the 10-15mph range during the day before increasing overnight to the 30-35mph range with gusts in the 50’s. Temperatures hovered in the mid 20’sF along ridgelines and the low-mid 30’sF at 1,000′.

Today: Skies are cloudy this morning and light snow showers are expected before skies try and break up later today (1-4″ accumulation above 500′, rain below). East ridgetop winds decreased early this morning and are forecast to average between 20-30mph with stronger gusts during the daytime hours. Temperatures are warm and could reach 40F today at sea level but should remain in the mid 20’sF along ridgelines. Tonight, another warm storm moves in with heavy snowfall (above 500′) and strong east wind (35-45mph).

Tomorrow: Heavy snowfall will continue on Saturday with rain creeping up to ~1,000′ midday as warmer air streams in. Strong east winds (35-45mph averages) will also continue with the system. The storm is expected to head out late Saturday night with around a foot of storm total and Sunday is still looking like a possible clearing day.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	tr	tr	131
Summit Lake (1400′)	29	tr	tr	45
Alyeska Mid (1700′)	32	3	0.3	116

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	NE	22	57
Seattle Ridge (2400′)	26	SE	19	32

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.