Fri, December 02, 2016 Turnagain Pass Avalanche Forecast

Fri, December 2nd, 2016

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		Moderate (2)
Treeline 1,000'-2,500'		Moderate (2)
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

Wind Slabs

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.

More info at Avalanche.org

A fast hitting and very interesting storm rolled through Wednesday night and into Thursday morning. We were excited to find 12″ of storm snow in the Seattle Ridge parking lot yesterday, but disappointment set in as only 6-8″ was found at the higher elevations. This seemed to be the case with the other ridgelines. In the end, this storm looks to have been a bit more blow than snow. That said, lingering wind slab avalanches are our primary concern today.

WIND SLABS: If you are headed out, watch for both older slabs from Wednesday’s storm and fresh slabs if the cold North winds bump up enough to move snow around. Most concerning is that wind slabs could be sitting on the Nov 16 layer of buried surface hoar. If this is the case, a ‘typical’ wind slab avalanche could step down and trigger a much larger slide releasing 2-3′ deep. Keep in mind, these could pop out mid-slope as the Todd’s Bowl image below illustrates. Pay attention to how the snow feels underfoot. Is it stiff? Does it feel upside down i.e. hard over soft? Do you see shooting cracks? Does it feel or sound hollow? Look for recent cornices, wind pillows and drifts. Is a slope cross-loaded or top-loaded?

Photo below: Natural avalanches in Todd’s Bowl during the tail end of Wednesday night’s storm. It is suspect that buried surface hoar was the weak layer in the two avalanches where the crowns can be seen mid-slope.

Avalanche Problem 2

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

A layer of buried surface hoar, 1-3′ deep, still remains on many slopes at Turnagain Pass and in the Summit Lake area. During the past two weeks, many popular slopes have avalanched (removing the weak layer), been covered again by snow and folks are skiing and riding them without incident. The trick is: figuring out where it has not avalanched and could it still? Questions to ask as we move into a weekend of clear-ish skies. Safe travel protocol is your best bet out there in case one of these deeper slides occurs.

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

It’s been roughly a week since we have seen or heard of a glide crack releasing – but the cracks continue to widen despite the cold weather. Once again, limiting your exposure under these is highly recommended.

Weather

Fri, December 2nd, 2016

Partly cloudy skies aloft with valley fog below filled the region yesterday. No precipitation fell during the day. Winds were light from the Southeast. Temperatures were in the mid 20’s F at all elevations with a spike to 30F at 2,000′ mid-day.

Overnight, an inch of snow fell in Girdwood Valley and Turnagain Pass with light easterly ridgetop winds. Today, continued flurries could pile up another inch. Ridgetop winds will shift to the North this morning and increase to 15-25 mph while ushering in a very cold air mass. Temperatures should drop today from ~25F to 10F on the ridgelines.

Tomorrow and through the weekend, the cold North flow will remain in place bringing partly sunny skies, cold Northerly winds and little chance for precipitation.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	26	1	0.1	23
Summit Lake (1400′)	23	0	0	4
Alyeska Mid (1700′)	26	1	0.1	13

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	NE	7	21
Seattle Ridge (2400′)	25	SE	7	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.