Mon, March 11, 2019 Turnagain Pass Avalanche Forecast

Mon, March 11th, 2019

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Considerable (3)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Considerable (3)
Below Treeline Below 1,000'		Considerable (3)

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

Triggering a large storm slab avalanche is still likely on steep slopes today and extra caution is advised. The snowpack still needs time to adjust to the recent load. The storm over the weekend brought 2-3 feet of snow and winds gusting above 100 mph. The snow fell on a variety of old snow surfaces including crusts, surface hoar and facets. There were a few natural avalanches that occurred during the storm reported yesterday. Observers in a couple of locations found the new snow bonding fairly well but overall there is still the potential for a large avalanche to be triggered. A few large whumpfs were experienced by groups in Turnagain and Summit Lake yesterday. Continued warm temperatures that can help the new snow bond to the old snow may first make the storm slab more cohesive and avalanches could be larger and more connected today. Wind-loaded areas are most suspect. High winds and heavy snow tend to make slabs lower down on the slope than expected, watch for pillowed areas and unusual loading. The winds also created some mid-storm layers that were reactive and noted in observations. As temperatures rose yesterday the snow became wetter and heavier at lower elevations. Roller balls and wet sluffs/push-a-lanches may be possible today in steep low elevation terrain as there was no freeze overnight near sea level. Steer clear of cornices and choose terrain carefully. It may not be the first skier or snowmachine on the slope that triggers the avalanche and there is still the potential to trigger an avalanche remotely.

Storm snow at 1500′ on Tincan yesterday. There was propagation at the new/old snow (small facets) interface, 3-10-19.

Obvious wind-loading and cornice growth in Hippy Bowl, 3-10-19.

Weather

Mon, March 11th, 2019

Yesterday: Broken skies, light rain/snow showers and easterly winds 10-20 mph with gusts into the 30s and 40s, easing off a bit mid-morning. Temperatures were in the 20Fs to mid 30Fs. Overnight mostly cloudy skies and easterly winds in the teens gusting to 30 mph. Temperatures stayed in the 20Fs and 30Fs.

Today: Mostly cloudy skies with temperatures in the high 20Fs to high 30Fs. Snow and rain showers are forecast with a couple of inches of snow expected and rain/snow line around 1000 ft. Winds will be southerly 10-15 mph with gusts into the 20s and 30s. Temperatures look to cool overnight dropping into the teens and 20s.

Tomorrow: Partly sunny with temperatures in the 20Fs and 30Fs. Chance of snow showers later in the day. Light winds increasing overnight into Wednesday. The next storm looks to impact the area Wednesday evening.

*Seattle Ridge wind sensor is not reporting.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	32	0	0	70
Summit Lake (1400′)	33	0	0	27
Alyeska Mid (1700′)	32	0	0.25	71

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	NE	15	49
Seattle Ridge (2400′)	28	*N/A	*N/A	*N/A

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
02/07/23	Turnagain	Observation: Seattle Ridge	Wagner / Keeler Forecaster
02/07/23	Turnagain	Avalanche: Pete’s North	Megan Guinn
02/05/23	Turnagain	Observation: Rookie Hill	Tony Naciuk
01/31/23	Turnagain	Observation: Johnson Pass area	Megan Guinn / W Wagner Forecaster
01/29/23	Turnagain	Observation: Tincan Backdoor	AAS-Level 1 1/27-1/30
01/28/23	Turnagain	Observation: Sunburst	Brooke Edwards
01/28/23	Turnagain	Avalanche: Seattle Ridge	W Wagner
01/28/23	Turnagain	Observation: Tincan Common	Tony Naciuk
01/27/23	Turnagain	Observation: Sunburst	John Sykes
01/27/23	Turnagain	Avalanche: Lynx Creek	Megan Guinn / W Wagner

Riding Areas

Updated Fri, January 06th, 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	Open	Opened Dec 13th.
Placer River	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Skookum Drainage	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Turnagain Pass	Open	Opened Dec 13th.
Twentymile	Closed	Closed Jan 5th due to lack of snow (holiday storms rained away the snow at sea level).
Seward District
Carter Lake	Open	Opened Dec 13th.
Lost Lake Trail	Open	Opened Dec 13th.
Primrose Trail	Open	Opened Dec 13th.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Open	Opened Dec 13th.
South Fork Snow River Corridor	Open	Opened Dec 13th.
Summit Lake	Open	Opened Dec 13th.