Sun, November 25, 2018 Turnagain Pass Avalanche Forecast

Sun, November 25th, 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

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

This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches

This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.

More info at Avalanche.org

CHANGING WEATHER AND INCREASING AVALANCHE DANGER

A warm, wet and windy storm is over the region currently. Roughly 10 to 12″ of snow has fallen in the Alpine zones with another 10 to 14″ expected today (above 2,500′). At the mid-elevations, roughly 6 to 10″ of wet snow has fallen with an additional 1″ of rain (yes rain) expected up to 2,200′ this afternoon. Easterly ridgetop winds will continue to be in the 20’s with gusts in the 50’s mph.

Although there was bare ground before this storm up to 2,000′, above this a shallow snowpack has been forming (see photos below). Rain last weekend followed by cool temperatures formed a crust up to the ridgetops on this pre-existing snow surface. The kicker is, surface hoar formed on the crust before it was buried yesterday. So, what we have is a perfect recipe for avalanche activity in the upper elevations. Any new snow accumulation is expected to slide off the old snow surface easily. How much avalanche activity we will have and how big those avalanches will be is directly related to how much snow falls. As of this morning, there is roughly a foot of snow from yesterday and another foot expected today – again, this is all above 2,500′. Therefore, storm slabs up to 2′ thick are possible and where winds have been loading up to 3 to 4+’ thick.

Snow falling along the road and up to ~2,200′ is expected to turn to rain by this afternoon. This will saturate and melt much of the 6 to 10″ of wet snow existing in these mid-elevations (1,000′ to 2,500′). The worry at these elevations is being in the runout zone of an avalanche from above where debris can run. All this said, today is a day to leave the mountains alone and look ahead to the cooler weather on tap for the middle part of the week!

Sunburst, above the alders – hard snow with suspected surface hoar on top existed before this storm rolled in yesterday (Saturday)

The pre-existing snow line was a little lower on Tincan, just above1500′

East facing slopes of Repeat Offender on Seattle Ridge on Friday, November 23. Snowline was around 2000′.

Looking into Lynx Creek drainage, Northern aspects before the storm on Friday.

Weather

Sun, November 25th, 2018

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	9	1	13
Summit Lake (1400′)	31	1	0.2	1
Alyeska Mid (1700′)	31	4	0.5	4

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	NE	21	46
Seattle Ridge (2400′)	30	E	11	33

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
12/10/19	Turnagain	Avalanche: Tincan and Sunburst from the air	CNFAIC Staff
12/10/19	Turnagain	Observation: Tincan	Nancy Pfeiffer
12/08/19	Turnagain	Avalanche: Tincan	Ryan Van Luit Forecaster
12/06/19	Turnagain	Avalanche: Sunburst	Billy Finley
12/04/19	Turnagain	Observation: Sunburst	A.Johnston-Bloom/ W.Wagner/ R.Van Luit Forecaster
12/03/19	Turnagain	Observation: Hippy Bowl	Nick Langowski
12/01/19	Turnagain	Observation: Tincan, All elevations	Eric Roberts
12/01/19	Turnagain	Observation: Tincan	Andy Moderow
11/30/19	Turnagain	Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge	Eric Roberts
11/29/19	Turnagain	Observation: Sunburst Ob #2	Aleph Johnston-Bloom Forecaster

Riding Areas

Updated Wed, December 11th, 2019

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.
Placer River	Closed	Closed.
Skookum Drainage	Closed	Closed.
Turnagain Pass	Closed	Closed.
Twentymile	Closed	Closed.
Seward District
Carter Lake	Closed	Closed.
Lost Lake Trail	Closed	Closed.
Primrose Trail	Closed	Closed.
Resurrection Pass Trail	Closed	Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor	Closed	Closed.
South Fork Snow River Corridor	Closed	Closed.
Summit Lake	Closed	Closed.