Share your feedback! Share your feedback!

How’s our new website?
How can we better serve you?

Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 2nd, 2020 - 7:00AM
Expires
Fri, January 3rd, 2020 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is MODERATE at all elevation bands. Triggering an avalanche breaking on a buried weak layer in the snowpack or a lingering wind slab is possible today. Watch your sluff and give cornices a wide berth. Evaluate snow and terrain carefully. Look for signs of instability, ease into steeper terrain and use good travel protocol.

Thanks to our sponsors!
Thu, January 2nd, 2020
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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

If you area venturing into the backcountry today it is important to keep in mind that triggering a large avalanche on the Solstice surface hoar/buried facets is a possibility and we are still in the 48 hour window after the New Year’s Eve storm. It is important to look for signs of instability but also remember they may not be present with this type of weak layer. Slowly progress into avalanche terrain and only expose one person at a time. With the improved snow cover it is possible to go to places in the advisory area that haven’t seen much traffic. Parts of the region with a shallower snowpack will be the most suspect i.e. Crow Pass, the southern end of Turnagain Pass including Lynx Creek and Summit Lake.  The weak layer is now buried from 1-4′ deep. Prior to the New Year’s Eve storm there had been reports of fairly widespread whumpfing (especially in the Treeline elevation band, including Seattle Ridge) and the Solstice surface hoar/buried facet layer was found to be reactive in some snowpack observations. Due to the highway closure we have limited snowpack data after the New Year’s Eve storm. What we do know is that it warmed up and then rained to 2200′-2500′. Some natural avalanches were observed around the region potentially failing on the buried weak layer but not that is not confirmed. It then cooled and rapidly switched to snow with 1-2′ ( or 4′ in Portage) of snow falling. There was not much observed avalanche activity associated with the colder part of storm or and temperatures have cooled down significantly since which should help the overall stability. However, it is important to remember today MODERATE does not mean LOW danger. The snowpack hasn’t had much traffic or testing.  Triggering a large, dangerous avalanche is still possible and whether you are traveling up, down or across avalanche terrain, caution is advised. Choose terrain wisely and avoid terrain traps.

Solstice buried surface hoar and facets are now buried by all the Dec 22-30 snowfall as well as the New Year’s Eve storm. The depth of the buried weak layer is variable across the region. Shallow snowpack areas are the most suspect. 

 

 

 

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

During the New Year’s Eve storm while the snow was falling, the winds were averaging in the 30s and gusting into the 60s likely loading leeward slopes and creating wind slabs just off the ridgelines and in cross-loaded gullies.  Look for drifting, cracking and hard snow over soft snow.  Avoid steep unsupported slopes with stiff snow. Remember even a small wind slab can be dangerous in high consequence terrain.

Cornices: Wet snow and wind in the Alpine during the warm part of the storm Tuesday likely added snow to the cornices already looming in the Alpine. Avoid travel on or underneath the cornices and pay attention to groups traveling above or below you.

Loose snow avalanches (sluffs): On the flip side if you are in protected steep terrain that is not wind effected watch your sluff. The cold temperatures will make the low density new snow even less cohesive and more likely move. Sluffs can be pushy and hazardous if you are in the wrong spot and get hit from behind. Some natural loose snow avalanches that occurred during the storm were observed yesterday.

Wind effect in the Alpine on Petes South, 1.1.20.

Corniced ridgeline, Petes North, 1.1.20

Weather
Thu, January 2nd, 2020

Yesterday: Mostly to partly cloudy skies. Light snow showers mainly near Girdwood Valley. Temperatures dropped from the teens to the single digits. Winds were easterly 5-15 with gusts into 30s. Overnight temperatures got down to below zero in some locations.

Today: Partly cloudy skies with a chance of light snow showers in Whittier and Portage later in the day. Temperatures will range from 10°F to -10°F. Winds will be light and easterly. Overnight temperatures will be mostly near or below zero from sea level to ridgetops.

Tomorrow: Partly sunny with continuing temperatures in the single digits. Winds will shift to the north and remain light. The overall pattern looks to be fairly quiet into next week with the exception of a possible outflow wind event. We are keeping tabs on this as the cold air set up over the region.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 6 0 0 46
Summit Lake (1400′) 4 0 0 16
Alyeska Mid (1700′) 7 1.6 0.17 40

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 0 NE 13 35
Seattle Ridge (2400′) 4 NA NA NA
Observations
Recent Observations for Turnagain Pass
Date Region Location
05/06/20 Turnagain Avalanche: Pastoral Peak, north face
04/10/20 Turnagain Avalanche: Wolverine
04/10/20 Turnagain Observation: Eddies lookers right shoulder
04/09/20 Turnagain Observation: Bench Peak
04/04/20 Turnagain Observation: Tincan
04/04/20 Turnagain Observation: Pete’s North
03/26/20 Turnagain Avalanche: Tincan – Proper (SW facing)
03/26/20 Turnagain Avalanche: Seattle Ridge
03/25/20 Turnagain Avalanche: Sunburst Uptrack @ 2000′
03/24/20 Turnagain Observation: Turnagain – Road Observations
Riding Areas
Updated Fri, May 01st, 2020

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
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

Subscribe to Turnagain Pass
Avalanche Forecast by Email

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.