Thu, December 01, 2016 Turnagain Pass Avalanche Forecast

Thu, December 1st, 2016

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Considerable (3)
Below Treeline Below 1,000'		No Rating (0)

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

Persistent Slabs

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.

More info at Avalanche.org

We received the lower end of forecasted snow amounts with only 5-7 inches falling across the advisory area. This might not seem significant but there are few important factors to keep in mind. First this fell on weak surface snow, second it came in with easterly winds blowing in the 20s and gusting as high as 60mph on Sunburst, third there was already soft snow available to transport and finally the temperatures were steadily rising throughout the storm so the snow will be upside down. Colder snow will be under warmer heavier snow. Then put this all on top of the surface hoar that has been the culprit in all of the avalanche activity in the last two weeks. This surface hoar sits 1-2 ft below the surface and has shown that it still has the potential to avalanche. It now has additional load on top of it and may have a more connected slab due to wind-loaded snow. Some slopes have slid on this layer and some haven’t. This combination warrants caution. It may be triggered remotely and may let you get out onto the slab before it breaks. The new snow and wind might have been the tipping point or your weight might be when you get onto the slope.

Today it will be important to look for recent avalanches, cracking and collapsing (whumpfing). In addition look for wind deposition, wind slabs, newly formed cornices and places where you feel stiffer snow over soft snow. Keep slope angles low and pay attention to what is above and below you. Remember the buried surface hoar when you are making your slope decisions.

Buried surface hoar picture taken November 19th. Photo: Wendy Wagner

This photo was taken yesterday, November 30th on Manitoba and the same layer is still visibly intact and still showed the potential to avalanche in stability tests.

Avalanche Problem 2

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

More info at Avalanche.org

The new snow last night fell onto weak surface snow, came in with wind and with a rise in temperature. Storm slabs may be easy to trigger even at lower elevations. Investigate whether the new snow is bonding to the old snow surfaces. Pay attention to cracking and collapsing.

Additional Concern

Glide Avalanches

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.

More info at Avalanche.org

Watch for glide cracks and remember to limit time under these, there have been a handful that released last week. *Several cracks have been opening in popular terrain like Tincan’s Common bowl and the SW face of Sunburst. These may be hard to see with new snow.

Weather

Thu, December 1st, 2016

Yesterday was overcast with light snow falling during the day. In the late afternoon snowfall picked up with a period of heavy snow from 3pm-7pm. Temperatures steadily rose throughout the day going from single digits into the high 20Fs. Sustained easterly winds blew 20-30 mph with gusting into the 60s.

Today will be mostly cloudy with snow showers. 0-3′” of new snow. East winds will be light 5-15mph and temperatures will be in the high 20Fs. Tonight the chance of snow showers continues with another 0-3″ possible. Winds shift to the north and temperatures drop into the low 20s and teens.

Tomorrow will be mostly cloudy with light north winds and temperatures in the low 20s. There is a cooling trend into the weekend and a chance for more snow early next week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	21	5	.5	22
Summit Lake (1400′)	20	3	.3	4
Alyeska Mid (1700′)	22	7	.7	11

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	16	ENE	30	63
Seattle Ridge (2400′)	18	ESE	17	41

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 Mon, May 15th, 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	Open	Chugach NF staff will be assessing daily after May 15th. Please keep machines on the snow and avoid brown spots to keep this area open as long as possible.
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.