Wed, November 28, 2018 Turnagain Pass Avalanche Forecast

Wed, November 28th, 2018

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		Considerable (3)
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

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

Yesterday was much like the previous few days will an additional inch of water falling in the advisory area. Rain/snow line was between 2500′ and 3000′. In the Alpine there has been significant snow load. Today triggering an avalanche in this elevation band is likely and avalanches could be large. There has been almost no visibility to see what has happened above the rain/snow line over the past 4 days and we have limited data on the overall snowpack structure. We do know that there were conditions for surface hoar and a melt-freeze crust before the storm. If you do venture into the mountains this is a day to proceed with caution and choose terrain carefully. Be on the lookout for signs of instability: recent avalanches, shooting cracks, and whumpfing.

Water totals at the mid-elevation snow stations for this storm cycle from Saturday through Tuesday:

Girdwood Valley at 1,700′: 5.1″ of water equivalent
Turnagain Pass at 1,880′: 4.1″ of water equivalent
Summit Lake at 1,400′: 1″ of water equivalent

If there is any snow left at treeline (2500′ and below) triggering a wet loose avalanche in the saturated snowpack is also possible before the temperatures cool down later in the day.

Magnum and Cornbicuit, November 26, 2018. Photo: Wendy Wagner

West and NW aspects of Tenderfoot, November 26, 2018. Photo: Heather Thamm

Weather

Wed, November 28th, 2018

Yesterday: Rain and snow throughout the day. Rain/snow line was between 2500′ and 3000′. An inch of water fell in advisory area. Winds were easterly 15-25 mph with gusts into the 40s. Temperatures were in the 40Fs at sea level and in the high 20Fs on Sunburst at 3800′.

Today: Light showers transitioning from rain to snow are forecast for today as cooler air moves into the area. Temperatures should slowly cool into evening starting in the mid 30Fs and dropping into the mid 20Fs. Chance of snow showers overnight. Winds will be easterly 5-15 mph with gusts in the 20s.

Tomorrow: Partly sunny with temperatures in the high 20Fs to low 30Fs. Light SW winds. There is some discussion about the next storm moving into the area over the weekend but timing, temperatures, and precipitation type are still uncertain.

*Seattle Ridge weather station stopped collecting wind data at 10 pm.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	0	1.1	13
Summit Lake (1400′)	35	0	0.1	0
Alyeska Mid (1700′)	36	0	1.16	0

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	27	NE	21	40
Seattle Ridge (2400′)	32	E *	7 *	32*

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.