Tue, April 09, 2019 Turnagain Pass Avalanche Forecast

Tue, April 9th, 2019

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

Glide Avalanches
Almost Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
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.

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

Glide avalanches continue to be the most concerning avalanche problem for anyone traveling in avalanche terrain. Glide cracks litter the slopes and could release into an avalanche at anytime. Cracks are predominatly opening at elevations below 3,000′ and on E, S and W aspects. They are not triggered by people and are very unpredictable and destructive to anything in their path. The last known glide crack to release into an avalanche was Sunday morning, just south of Turnagain Pass near the Hope Wye cutoff. What we can do is keep our eyes open and limit/avoid traveling under cracks (example photo below). This may take some creative route planning in places, but it could be well worth it if a crack decides to release in your vicinity.

WET LOOSE: Triggering a wet loose avalanche (sluff) on steep slopes that did not freeze overnight is possible. This will be most likely on slopes below 2,000′ that have been soaked by rain and remain wet and unsupportable.

Glide cracks on Tincan under Common Bowl.

Avalanche Problem 2

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

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

It may be wet and raining down low, but it’s still relatively dry up high. Above 2,500′, anywhere from 1-6″ of new snow fell over the region yesterday (favoring Girdwood) which was added to the 3-6″ of new snow from over the weekend. Plug in moderate easterly ridgetop winds and we can expect 4-10″ thick wind slab on leeward facing slopes. Shaded aspects will be the most touchy as wind slabs are sitting on weak older snow (facets/buried surface hoar). One of these slabs was found on the North Chutes on Tincan Sunday (photo below). Keep a lookout for wind deposited snow, fresh drifts and watch for cracking around your skis/board or machine. Even a small wind slab can be a problem in steep rocky terrain.

Small, shallow skier triggered wind slab on one of Tincan’s north facing chutes on Sunday. (Photo Adam Baxter)

CORNICES: Cornices remain very large along some ridgelines in the Alpine. These cornices can break suddenly and pull back onto flat ground above a slope. Give them a wide berth and avoid travel directly below them.

South of Turnagain in Summit Lake and areas in the interior Kenai Peninsula still posses a variety of old weak layers within the snow pack. Be aware of a variety of avalanche conditions ranging from small isolated wind slabs to wet loose. Triggering a persistent slab 2-3′ deep is becoming an outlier at this point, but the poor snowpack structure is worth noting if headed to Summit.

Todd’s Bowl and the North facing Chutes of Tincan at Turnagain Pass. Winter remains at these higher elevations.

Weather

Tue, April 9th, 2019

Yesterday: Cloudy skies with light rain fell up to 2,000′ over the region. Girdwood picked up just under 1/2 an inch of rain, while Turnagain Pass saw around a tenth of an inch in the past 24-hours; this equates to 4-6″ of snow above 2,500′ and 1-2″ respectively. Ridgetop winds have been moderate, averaging 10-20mph with gusts near 40mph from the east. Temperatures climbed to the upper 20’sF at 4,000′ and the mid 40’sF at 1,000′ before dropping to the mid 20’sF at 4,000′ and the mid 30’sF at 1,000′.

Today: Mostly cloudy skies, with a few breaks in cloud cover, are in store today as a weak low pressure spins in the Eastern Gulf. A few raindrops may fall up to 2,000′ with flurries above this in favored areas. No measureable precipitation is expected. Ridgetop winds should remain moderate from the east in the 10-20mph range with gusts into the 30’s at times. Temperatures will be on a slow decline as cooler air moves in and highs near 40F are expected at 1,000′, while ridgetops remain in the mid 20’sF.

Tomorrow: A brief break between systems should bring partly cloudy skies, mild temperatures and light easterly winds for Wednesday. A powerful front is forecast to hit the region Thursday bringing heavy rain, 4-10″ of snow above 2,000′ and 50-70mph winds. Stay tuned!

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	37	rain	0.1	63
Summit Lake (1400′)	37	0	0	19
Alyeska Mid (1700′)	35	0.5	0.42	57

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	27	NE	14	39
Seattle Ridge (2400′)	31	SE	11	20

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.