Sun, March 15, 2020 Turnagain Pass Avalanche Forecast

Sun, March 15th, 2020

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

The weather forecast for today calls for clear sunny skies, calm to light west winds, and temperatures peaking near the freezing level at 3000′.

As the sun and increasing temperatures affect the region today, surface conditions could become less stable and also impact our sporadic persistent slab concerns found within the top 1′-2′ of the snowpack. An observer shared images illustrating the wet/moist loose avalanche concern from yesterday afternoon. Steep slopes on easterly, southerly, and westerly solar aspects where slopes heat up enough are the most likely spots for a person to initiate these avalanches. If triggered, this avalanche concern is expected to be on the smaller side of the scale, but could become entrained and move a rider or skier down the fall line. Remain aware of your surroundings and anticipate your exit strategy as the terrain dictates.

The snowpack in more remote areas could be quite different. Pay attention to signs of recent avalanches, cracking/whumpfing, wind effect, and sun effect. Also, keep in mind areas with a shallow snowpack are more likely places to find a slab that fails in the weak layer described above or other old weak snow buried in the pack. This includes the south end of Turnagain Pass, such as Twin Peaks and Silvertip to Summit Lake and over toward Palmer Creek and the Raggedtop area near Girdwood.

A skier initiated wet loose avalanche on a southerly aspect of Magnum. 3.14.2020 Photo: Allen Dahl

Loose snow: Loose dry snow still exists in many areas, especially on northerly aspects. On steep slopes where this is the case, sluff could be easy for a human to initiate and could move down slope with enough volume to take a person off their feet.

Cornices: We have some large cornice formation in many areas. As the sun and increased temperatures beat down, it could become easier to trigger these. As usual, it’s prudent to give cornices a wide berth and limit your time beneath them.

Weather

Sun, March 15th, 2020

Yesterday: Sunny skies with light ridgetop winds from the west. Temperatures warmed to the mid 20’s°F along ridgetops and 30°F at the lower elevations.

Today: More clear skies and sun! West winds are expected to be calm to light with temperatures just above freezing at sea level and 24°F-30°F at 3000′.

Tomorrow: More sun during the day with a high near 34°F at sea level. West winds are expected around 5 mph. In the evening, winds are expected to shift becoming southwest as clouds increase to set up Tuesday for possible precipitation.

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

	Temp Avg (F)	Snow Depth (in)
Center Ridge (1880′)	22	67
Summit Lake (1400′)	19	30
Alyeska Mid (1700′)	23	77

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	WSW	7	14
Seattle Ridge (2400′)	25	VAR	1	5

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.