Sat, December 03, 2022 Turnagain Pass Avalanche Forecast

Sat, December 3rd, 2022

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)

Recent Avalanches

We saw a few small natural wind slabs yesterday on Magnum that probably released during the last wind event on 12.1.22. Otherwise the last observed avalanche activity were small natural wind slabs last weekend during the 11.25-26 outflow wind event.

Avalanche Problem 1

Persistent Slabs
N E S W NW NE SE SW

Aspect/Elevation
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.

Aspect/Elevation of the Avalanche Problem

Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

The last known avalanche activity on the facet layer on the ground was back on 11.13.22, nearly three weeks ago. We are keeping it in the forecast due to uncertainty about the distribution and sensitivity of this layer at higher elevations. Our recent snowpit tests have shown a mixture of results, with some areas producing full propagation on this layer and other areas having no results. This is pretty typical for a deeply buried persistent weak layer. While we think it is unlikely for a person to trigger an avalanche 2-4′ deep on this layer today, we are still looking for more information from higher elevations (above 3000′) so please submit an observation if you get a chance to test this layer today!

There is also a possibility of finding a lingering wind slab up to 1′ deep today. The most recent round of wind slabs formed on 12.1.22 on top of a layer of near surface facets which can help them stay reactive longer than normal. These are most likely to be found in steep terrain along upper elevation ridgelines and cross loaded gullies. Keep an eye out for firm hollow feeling snow and shooting cracks to identify areas that could be holding onto a stubborn wind slab.

Finally, the clear skies this week have lead to faceting on the surface in areas protected from the wind which can lead to fast running loose snow avalanches (aka sluffs). If you are travelling in steeper terrain today be aware of your sluff because they can easily knock you off balance. We recommend always using safe travel practices to limit the exposure of your group to avalanche terrain. Travelling one at a time, spacing out, and always spotting your partners are critical to manage your avalanche risk even when it has been awhile since a recent snowfall event.

Mixture of soft snow and wind hardened snow in alpine elevations. Photo 12.2.22

Weather

Sat, December 3rd, 2022

Yesterday: A strong inversion was in place yesterday, with temperatures remaining in the single digits at the road elevation and reaching up to the low 30s at upper elevations. Winds were light, averaging 5-10 mph with gusts into the teens at upper elevations. High clouds moved into the area but the sun still shined through.

Today: Temperatures are getting downright balmy at upper elevations, as of 4am Sunburst weather station is reporting 35 F and Portage is reporting 2 F. That is one strong inversion! Temperatures at lower and mid elevations are expected to increase slightly later this afternoon, but the inversion should remain in place through the weekend. Winds will remain light with averages of 0-10 mph today. Some high level cloud cover is expected in the area today.

Tomorrow: Sunday looks like a repeat of Saturday except with clearer skies. A storm should to move into the area on Monday and provide us with a little refresh of snowfall on Monday afternoon and evening.

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

	Temp Avg (F)	Snow Depth (in)
Center Ridge (1880′)	21	22
Summit Lake (1400′)	9	15
Alyeska Mid (1700′)	21	20
Bear Valley (132′)	6	–

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	31	W	7	18
Seattle Ridge (2400′)	29	SW	2	7

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.