Sat, April 16, 2022 Turnagain Pass Avalanche Forecast

Sat, April 16th, 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)

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

Our area remains stuck between a low pressure system in the Bering Sea and a high pressure system in interior Alaska and Canada, which has caused increased wind speeds and cloud cover over the past 24 hours along with occasional light snowfall or rain. Winds and cloud cover are expected to decrease throughout the day and no significant precipitation is expected today. Lingering wind slabs created over the past 24 hours are the primary avalanche problem and could be up to a foot deep and possible for a human to trigger. To identify areas with recent wind loading look for signs of wind transport on the snow surface, hollow feeling snow, and shooting cracks along ridgelines, cross loaded gullies and convex rollovers. These wind slabs should be isolated to upper elevation areas that had stronger winds yesterday (see obs here and here).

If the cloud cover decides to really back off and the sun makes an appearance today then we could see wet loose avalanches on solar aspects, cornice fall from solar warming, and more active glide avalanche activity (see problem 2). Over the past week cool temperatures have been holding spring at bay and minimizing the amount of melt on solar aspects. However, a large wet loose avalanche on Penguin Ridge on Thursday is a good reminder that in steep terrain with enough melted snow at the surface you can easily trigger a wet avalanche large enough to bury a person. Be aware of how much melt is happening on southern aspects today if the sun comes out and avoid travelling on slopes that are more than ankle deep with melted snow.

Mostly cloudy conditions yesterday kept the sun from melting much, but if the clouds clear today wet loose avalanches and cornice fall could be an issue again. Photo 4.15.22

Avalanche Problem 2

Glide Avalanches
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

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

Glide avalanche activity has been widespread on southern aspects in Turnagain Pass and throughout the forecast area this week. Plenty of glide cracks remain that have not released yet and we should be extra careful to avoid spending time underneath glide cracks during this period of higher likelihood for them to release. Some of the most notable glide cracks still waiting to release are on Repeat Offender just south of the motorized up track. The avalanches created by glide crack releases are typically very large and destructive because they involve the entire depth of the snowpack and often have wet snow in the debris. This is one type of avalanche you do not want to mess around with!

Lots of glide cracks poised to release on the northern end of Seattle Ridge as the spring melt continues. Photo 4.15.22

Weather

Sat, April 16th, 2022

Yesterday: Overcast to mostly cloudy with occasional snow flurries during the day. Winds were light in the treeline elevation band and moderate at upper elevations with averages in the 5-15 mph range and gusts up to 35 mph along ridgelines.

Today: Similar to yesterday, but with decreasing winds speeds and cloud cover throughout the day. Temperatures should be in the 30’s at lower elevations and 20’s at upper elevations. Snow flurries are possible and most likely along coastal areas.

Tomorrow: Over the weekend and into early next week we are positioned at the boundary between a low pressure system in the Bering Sea and a high pressure system over the Alaska and Canadian interior. Occasional flurries and variable cloud cover are likely, but no significant precipitation is expected. Temperatures should remain relatively steady and wind speeds should stay light into early next week.

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

	Temp Avg (F)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	0.1	108
Summit Lake (1400′)	32	0.3*	37
Alyeska Mid (1700′)	34	0	NA

*Forecaster Note: Low confidence that this much precipitation happened in the last 24 hours in Summit Lake, this is likely an anomaly of the weather stations sensors.

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	E	12	35
Seattle Ridge (2400′)	24	SE	11	19

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.