Tue, March 02, 2021 Turnagain Pass Avalanche Forecast

Tue, March 2nd, 2021

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

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

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

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

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

With fairly quiet weather on tap for today, our main concern is triggering an avalanche 1-3’ deep on persistent weak layers that were buried in late January and early February. For anyone who has been following the advisory, these layers are old news by now. But that doesn’t mean we can ignore them. We have seen avalanches fail on these weak layers as recently as Sunday– clear evidence that they are still a problem. With incremental loading during the month of February, we have slowly buried these layers deeper and deeper. They are slowly gaining strength, and although we do not expect to see a widespread cycle without a major loading event, it is still possible to trigger avalanches big enough to bury a person.

These persistent weak layers are a real test of patience, with potentially severe consequences if we don’t treat them with caution. The only way to manage a problem like this is to realize that most steep slopes have the potential to avalanche, and to treat them accordingly. If you are trying to access steep terrain, avoid slopes with terrain traps like cliffs, trees, rocks, and gullies. Now is not the time to push it into big terrain. Be smart with safe travel protocol, only exposing one person at a time to steep slopes, and watching your partners from safe spots out of the avalanche path. If you are interested in digging in a little deeper, this post from the Utah Avalanche Center shares good insight regarding safe travel protocol, and how being better with group management can reduce fatal accident rates.

Wind slabs: Light winds today and yesterday are not likely to form large or widespread wind slabs, but it will still be attention to pay attention to signs of recent wind loading– especially in the most suspect terrain below ridgetops, convexities, and in cross-loaded gullies. It may still be possible to find small reactive wind slabs on isolated features.

Sluffs: With 2-6” new snow in the past 24 hours, we can expect to see dry loose avalanches (sluffs) in most steep terrain. It is unlikely these will be large enough to bury a person, but they can have serious consequences if they carry you over terrain traps.

Small wind slab releasing on a test slope in the Tincan trees yesterday. 03.01.2021

Two persistent weak layers in the upper snowpack on Tincan. 03.01.2021

Weather

Tue, March 2nd, 2021

Yesterday: Light snow showers through the day brought 2-4” snow under cloudy skies. High temperatures were in the mid to upper 20s F, with lows in the single digit to mid teens F, dipping just below 0 F at Summit Lake. Winds were light out of the east at 5-10 mph for most of the day, and shifted to the west yesterday evening.

Today: We should see quiet weather today, with partly cloudy skies and light westerly breezes around 5 mph. High temperatures are expected in the mid teens to upper 20s F, with lows in the single digits to mid teens F. We might see a few snowflakes during the day, but no accumulation is expected.

Tomorrow: Expect another day of quiet weather tomorrow, with mostly sunny skies and calm to light northwesterly winds around 5 mph. High temperatures should be in the mid teens to mid 20s F, with no precipitation expected. Our chances for snow are looking better towards the end of the week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	16	2	0.3	114
Summit Lake (1400′)	14	3	0.2	47
Alyeska Mid (1700′)	19	3	0.4	119

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	11	E-W*	8	30
Seattle Ridge (2400′)	12	SE-N*	5	21

*Wind direction changed around 4 p.m. yesterday

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.