Turnagain Pass Avalanche Forecast

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.

Issued

Tue, November 27th, 2018 - 7:00AM

Expires

Wed, November 28th, 2018 - 7:00AM

Forecaster

Aleph Johnston-Bloom

The Bottom Line

As wet and stormy weather continues today the avalanche danger remains HIGH in the Alpine. With additional snowfall and wind loading natural avalanches are likely. Avalanches at upper elevations may run into terrain below keeping the danger at CONSIDERABLE for the Treeline elevation band. Human triggered avalanches are very likely above the rain/snow line (approximately 2500′). Travel above treeline is not recommended.

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Tue, November 27th, 2018

Alpine
Above 2,500'

High (4)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		High (4)
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

Storm Slabs
Almost Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

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.

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

With the active weather the avalanche danger remains elevated. Snow at upper elevations and rain at lower elevations is expected to continue today. Rain/snow line is forecast to be around 2500′. Winds are forecast to be easterly with gusts into the 40s. Our road observations yesterday had limited visibility but a few wet loose avalanches were observed to have run in the mid-elevation band. Rain continues to wash away the snow that fell on Saturday night in this elevation band.

Water totals at the mid-elevation snow stations for this soggy storm cycle:

Girdwood Valley at 1,700′: 4″ of water equivalent
Turnagain Pass at 1,880′: 3″ of water equivalent
Summit Lake at 1,400′: 0.9″ of water equivalent

If we convert the water to snow at upper elevations we have a significant load. We are uncertain at this point about avalanche activity in the Alpine. However snow continues to fall, the winds are sustained and we know this is loading older layers of snow. With this recipe we have to expect storm slab avalanches.

Rookie Hill with a few small wet loose avalanches in the channeled terrain on Seattle Ridge. November 26, 2018, Photo: Wendy Wagner

Tincan: Snow that fell Saturday night in the mid-elevation band getting rained on. November 26, 2018. Photo: Wendy Wagner

Weather

Tue, November 27th, 2018

Yesterday: Rain and snow throughout the day. Rain/snowline was around 2500′. Temperatures were in the high to mid 30Fs at lower elevations and low 30Fs to high 20Fs at upper elevations. Winds were easterly 15-25 mph with gusts into the 40s.

Today: As a low in the Gulf continues to push moisture and warm air into the region rain and snow showers will continue. Half to three quarters of an inch of water is forecast to fall. Rain/snowline will remain around 2500′ before lowering Wednesday as cooler air moves in. Winds will be from the E-SE 20-30 mph with gusts into the 40s. Temperatures will be in the 40Fs to high 20Fs depending on elevation.

Tomorrow: A trough bringing cooler air is forecast to push up Cook Inlet with the potential to bring snow to Anchorage and Hatcher Pass. The advisory area should see a shift to snow showers with cooling temperatures later in the day into Thursday. The timing on all this is fairly uncertain as the weather models are not in agreement.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	36	0	0.8	13
Summit Lake (1400′)	35	0	0.4	0
Alyeska Mid (1700′)	36	0	1.59	0

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	NE	16	50
Seattle Ridge (2400′)	32	E	11	40

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/25/22	Turnagain	Observation: Sunburst	Hannah Smith
11/25/22	Turnagain	Observation: Sunnyside / Seattle Ridge	Matti Silta
11/25/22	Turnagain	Observation: Sunburst	John Sykes
11/25/22	Turnagain	Observation: Tincan Trees	Andy Moderow
11/25/22	Turnagain	Observation: Tincan	Galen Hecht
11/25/22	Turnagain	Observation: Top of Seattle Ridge uptrack	Nick Crews
11/24/22	Turnagain	Avalanche: Sunnyside/Main Bowl	Andy Moderow
11/23/22	Turnagain	Avalanche: Seattle Ridge	John Sykes Forecaster
11/23/22	Turnagain	Observation: Tincan Trees	Brooke Edwards
11/23/22	Turnagain	Observation: Tin Can Common Bowl	Melanee Stiassny

Riding Areas

Updated Sat, November 26th, 2022

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	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass	Closed	The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.

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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.

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