Sun, December 18, 2016 Turnagain Pass Avalanche Forecast

Sun, December 18th, 2016

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Considerable (3)
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

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

More blow than snow…? It looks like this may be the case for the storm that will be quickly moving through today. As of 6am this morning, Easterly ridgetop winds have jumped up and are averaging in the 30’s mph. Snowfall has just begun in Girdwood and a trace has fallen on Turnagain Pass. If you are thinking of heading out today, expect quite windy conditions and increasing avalanche hazard.

We are expecting anywhere from 2-6+” of new snow today. In favored areas, with over ~5″ of new snow, we can expect the strong winds to form slabs quick enough that they release naturally. In areas with lower snow amounts, new wind slabs should be relatively shallow (6-10″). Slabs could also be a bit stubborn to trigger – keep this in mind as they could allow you to get out onto them before they release. Another thing, slabs may be thicker than expected if formed over Friday’s wind slabs, adding to the consequences. Remember, expect any slab you find to be sitting on weak faceted snow and poor bonding is likely.

What to watch out for:

Areas with current wind loading (winds should blow all day)
Slabs lower on slopes from cross-loading
Stiff snow over softer snow (punchy snow)
Cracks shooting from your feet
Whumfing sounds (collapsing of the snowpack into the faceted snow underneath)

Photo: Wind effect on the Sunburst Ridge yesterday. In the back you can see the cross-loaded Northerly slopes on Magnum. (Thanks to Sam Galoob for sending us this picture and report)

Avalanche Problem 2

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

Watch for fresh cornice growth. Small chunks of fresh pieces of cornice are likely to fall today.

Weather

Sun, December 18th, 2016

During the past 24 hours we have seen partly cloudy skies and no precipitation. Ridgetop winds were light yesterday and are ramping up this morning from an Easterly direction. Temperatures sit in the upper 20’s F at the lower elevations up to treeline and have cooled slightly on the ridgelines to the upper teens.

Today, we will be on the North edge of a large area of low pressure heading East. This will usher in strong wind and some snowfall. Easterly ridgetop winds are on the rise currently and should peak with averages around 30-40mph and gusts 70-80mph. Snowfall numbers are unfortunately meager with only 3-5″ expected on Turnagain Pass, 1-2″ in Summit Lake and 8-10″ in the Portage Valley. The good news with the low staying so far South is temperatures should remain cool with a rain/snow line around sea level to 200′. Ridgetop temperatures will stay close the 20F with 1,000′ temps in the upper 20’s F.

An unsettled weather pattern will continue into the work week – it’s difficult to tell what kind of snow amounts we will see – stay tuned tomorrow morning!

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	26	trace – 1″	0.1	23
Summit Lake (1400′)	21	0	0	8
Alyeska Mid (1700′)	28	0.5″	0.06	15

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	19	NE	15	56
Seattle Ridge (2400′)	22	SE	12	27

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.