Thu, November 29, 2018 Turnagain Pass Avalanche Forecast

Thu, November 29th, 2018

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

No Rating (0)

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

Very Large

Large

Small

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

Last night was the first freeze in five days since a series of warm and wet storms ended yesterday morning. Not much snow exists below 2000′ due to heavy rain that may have reached ridgetops at times. We don’t have a lot of information from the upper elevations, above 2500’, at this point. We know 4+’ of snow fell over a four-day period and strong Easterly winds have loaded leeward features and cross-loaded other aspects. Prior to this storm a melt-freeze crust and surface hoar formed in the upper elevations. We don’t know how much avalanche activity occurred during the storm and if this poor structure is lingering in places that haven’t avalanched.

Today triggering an avalanche is possible in the Alpine and could be large enough to bury a person. If you hike into the Alpine where there is enough snow to slide ease into avalanche terrain with a cautious mindset. We are still in the 48-hour period since heavy snow and strong winds formed storm slabs. Avoid avalanche terrain if you observe any signs of instability: recent avalanches, shooting cracks, or whumpfing.

Webcam pictures from DOT weather station provided our first glimpse into the Alpine yesterday afternoon – Northern and Western aspects of Tincan above 2000′.

Brief clearing in the afternoon provided a nice glimpse of an Eastern aspect of Seattle Ridge. Note how little snow exists in the lower elevations.

West aspect of Butch in foreground and Northern aspects of Tenderfoot and Tri-Tip in the background. Photo from Mon Nov. 26 at Lower Summit Lake.

Weather

Thu, November 29th, 2018

Yesterday: Moderate Easterly ridgetop winds diminished yesterday morning becoming light by early evening. Skies were obscure most of the day a broken period late afternoon. Temperatures dropped below freezing last night allowing 0.1 € of snow water equivalent to fall as an inch of snow to sea level from Girdwood to Turnagain Pass last night.

Today: Scattered snow showers and a trace of snow are possible this morning with clearing skies in the forecast this afternoon. In the upper elevations temps will average in the low 20Fs and upper 20Fs near sea level. Winds will remain light and variable.

Tomorrow: Temperatures will start to increase as another storm moves into our region Friday into Saturday. This storm will have a Southwesterly flow, which typically favors Hatcher Pass for precipitation. Temperatures are expected to reach above freezing and rain is likely in the mid and lower elevations. Increasing temps and winds are expected in the Western Chugach and Kenai Mountain.

*Seattle Ridge weather station stopped collecting wind data at 10 pm on Nov 27, 2018.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	29	1″	0.1	10
Summit Lake (1400′)	27	0	0	0
Alyeska Mid (1700′)	30	1″	0.16	*N/A

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	21	ENE	5	27
Seattle Ridge (2400′)	26	*N/A	*N/A	*N/A

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/28/22	Turnagain	Avalanche: Turnagain Pass – late May wet slab cycle	CNFAIC Staff
05/21/22	Turnagain	Avalanche: Magnum, Lipps and Tincan	CNFAIC Staff
05/17/22	Turnagain	Avalanche: Sunburst	CNFAIC Staff
05/17/22	Turnagain	Observation: Tincan Ridge	Joe Kurtak
05/11/22	Turnagain	Avalanche: Cornbiscuit and Magnum west faces	CNFAIC Staff Forecaster
05/07/22	Turnagain	Observation: Granddaddy	Kit Barton
04/29/22	Turnagain	Observation: Sunburst wx station	AS/ MM/ AM/ NH
04/28/22	Turnagain	Observation: More Turnagain Pass/Summit Lake wet slab activity	Alex Marienthal
04/27/22	Turnagain	Observation: Magnum	Sykes / Buttrick Forecaster
04/27/22	Turnagain	Observation: Girdwood/Summit/Turnagain Road obs	A S

Riding Areas

Updated Wed, June 01st, 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	Closed as of May 1 per Forest Plan.
Placer River	Closed	Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage	Closed	Closed as of April 1st per Forest Plan.
Turnagain Pass	Closed	Closed as of June 1st.
Twentymile	Closed	Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake	Closed	Closed as of May 1 per Forest Plan.
Lost Lake Trail	Closed	Closed as of May 1 per Forest Plan.
Primrose Trail	Closed	Closed as of May 1 per Forest Plan.
Resurrection Pass Trail	Closed	Closed as of May 1 per Forest Plan.
Snug Harbor	Closed	Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor	Closed	Closed as of May 1 per Forest Plan.
Summit Lake	Closed	Closed as of May 1 per Forest Plan.