Mon, April 08, 2019 Turnagain Pass Avalanche Forecast

Mon, April 8th, 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

A large glide avalanche was observed east of the Hope Wye yesterday morning and glide cracks have been appearing, opening and releasing across our region over the last two weeks. This is the entire snowpack gliding downhill and spontaneously releasing. So far all of this activity has occurred on East, South, and West facing slopes below 3000’. This past week Turnagain Pass has been the most active. Glide avalanches are not associated with a human trigger and release without warning. The best way to manage this problem is avoidance. Identify existing cracks and plan your route to avoid being under a glide. Many cracks are opening in popular terrain and may require an unusual route to avoid their runout. This is a case of ‘don’t be caught in the wrong place at the wrong time’.

Recent glide avalanche observed in the morning, 4-7-19

Closer view of the recent glide next to an older release, 4-7-19.

Avalanche Problem 2

Wet Loose
Almost Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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

Yesterday brought broken skies, some on and off very light rain/snow and warm temperatures in mid 40Fs at 1000′, and 30Fs in the Alpine. With overnight cloud cover, the snowpack did not get a chance to freeze leaving a deteriorating crust and wet/moist snow on the surface of solar aspects. Triggering a wet loose avalanche will be possible with today’s continued weather pattern of light rain and snow across the region, warm temperatures and a chance of sunshine. Pay close attention to the surface conditions, roller balls and wet snow sluffs above 2500′. At lower elevations monitor the crust as it becomes punchy and unsupportable.

WIND SLAB: Keeping in mind the few soft inches of snow that fell over the weekend (3-6″) was blown onto leeward slopes and there is still snow available for transport on shaded aspects in the Alpine. Yesterday observers noted that the new snow was not bonding well to the small facets and surface hoar found at the new/old interface on the shaded aspects and shallow skier triggered wind slabs were reported. With easterly winds today between 10-25 mph, gusting up to 40mph, triggering a small shallow wind slab in steep leeward terrain features remains possible. Watch for cracking and look for pillowed snow along ridgelines. Be cautious of fresh drifts.

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.

New snow sliding easily off on small facets and surface hoar at the old snow interface, 4-7-19.

Weather

Mon, April 8th, 2019

Yesterday: Broken skies with very light rain/snow showers on and off throughout the day. Rain/snowline was around 2500′. Winds were easterly 5-15 mph gusting into the 20s. Temperatures were in the 40Fs at lower elevations and the 30Fs to high 20Fs at upper elevations. Overnight skies were mostly cloudy and temperatures were in the 40Fs to high 20Fs depending on elevation. Easterly winds bumped up slightly gusting into the 30s.

Today: Mostly cloudy skies with rain and snow likely throughout the day and the rain/snowline near 2500′, with an overall accumulation up to a couple of inches of snow in the upper elevations. Temperatures will be in the 40Fs at sea level, and in the 30Fs in the upper elevations. Winds will be easterly between 10-25mph, gusting into the 40s.

Tomorrow: Similar weather is forecast as the series of low-pressure systems continue to move through the advisory area bringing more rain/snow showers, warm temperatures and gusty easterly winds. This pattern looks to continue throughout the upcoming week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	38	0	0	63
Summit Lake (1400′)	39	0	0	19
Alyeska Mid (1700′)	38	0.06	0	57

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	NE	11	38
Seattle Ridge (2400′)	33	E	4	21

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.