Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, February 22nd, 2022 - 7:00AM
Expires
Wed, February 23rd, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE on all aspects and elevations. Human triggered avalanches composed of the new snow from last night will be likely. These will be storm slabs, wind slabs, sluffs and cornice falls. Avalanches will be larger and more dangerous in the Girdwood, Placer, and Portage Valleys where the highest snowfall amounts occurred (12-20″). As the storm exits, natural avalanches remain possible. The new snow has fallen on a weak layer of surface hoar, which could create larger slab avalanches than expected. Additionally, avalanches have the possibility to step down into old weak layers of the snowpack, creating an even larger avalanche.

*Despite the improving weather today, dangerous avalanche conditions exist. A cautious mindset with careful snowpack evaluation skills are recommended for safe travel in the backcountry.

SUMMIT LAKE:  Avalanches could break in older weak layers in the Summit Lake area, to the south of the forecast area, creating large and dangerous avalanches. Avoiding avalanche terrain in these shallow snowpack areas on the Kenai is recommenced.

Roof Avalanches:  Warm temperatures will allow roofs to continue to shed.

Special Announcements
  • Hatcher Pass Avalanche Center has issued a HIGH avalanche danger for their zone. Be sure to see today’s forecast at hpavalanche.org!
Thanks to our sponsors!
Tue, February 22nd, 2022
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    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

Another storm moved through Southcentral yesterday afternoon, peaked around midnight last night, and is exiting the area this morning while the last 1-3″ of snow falls. The storm favored the Girdwood, Placer and Portage Valleys where 12-20″ of new snow fell in 18 hours. Turnagain Pass only received about half that (6-10″). But… everyone got hit by the strong easterly ridgetop winds, which blew 30-50mph with gusts near 70.

Storm snow total estimates at 2,500′ as of 6am:
Turnagain Pass:  6-10″ snow
Girdwood/Portage Valley:  12-20″ snow
Summit Lake (outside advisory area):  3-5″ snow

In the Girdwood/Portage/Placer zones, the danger likely rose to HIGH last night during the peak of the storm. This means we can expect to see signs of natural avalanches today. These should be storm slabs, wind slabs, sluffs and cornice falls, all associated with the new snow. Additionally, avalanches could have broken in buried weaker layers, creating a much larger avalanche, similar to what we saw last Friday. With lesser snow at Turnagain Pass, we can expect to see signs of mostly wind slab avalanches and possibly some cornice falls.

Even though the storm is abating, there could still be some avalanches that occur naturally today. What will be likely are human triggered avalanches. The new snow fell on a layer of surface hoar and this could allow storm slabs or wind slabs to propagate wider than expected. Avalanches could also be triggered remotely from a ridge, from the sides, or below a slope. We have to assume the surface hoar that was buried will create avalanches until proven otherwise. Storm slabs will be as deep as the new snow and wind slabs could be anywhere from 1-4′ deep depending on the amount of wind loading and new snow.

It is a day to closely assess the amount of new snow and expect that new snow to avalanche easily. Any wind loaded slope should be off limits, even in areas that only saw around 6″ or less of new snow. In addition to assessing new snow amounts and new wind loading, watch for signs of recent avalanches, cracking in the snow around you, and for collapsing (whumpfing) in the snowpack. All these signs should be prevalent today.

 

Surface hoar formed over the weekend that was buried by the new snow last night. This layer could significantly impact the snow from bonding and allow avalanches to be wider than expected. Photo Andy Moderow, 2.20.22.

Avalanche Problem 2
  • 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

As mentioned above, there are areas of the forecast zone where an avalanche could step down to a buried weak layer. This could be those old November facets on top of the Halloween crust or weak snow around the old New Year’s crust. It is the thinner snowpack zones where this is most likely, such as the western side of Girdwood Valley (Crow Pass area for example) and south of Turnagain Pass (Silvertip, Summit Lake areas).

Additionally, the interface from Valentine’s Day, that was buried around 1-2′ deep over the weekend, was the weak layer in many avalanches around Turnagain Pass on Friday. This layer could still be capable of producing avalanches in places it has not fully bonded. If that is the case, new snow avalanches could possibly step down to this interface. All in all, there are multiple layers that could be overloaded and another reason to dial it back significantly today.

Weather
Tue, February 22nd, 2022

Yesterday:  A storm moved in yesterday with winds picking up in the morning along with snowfall around noon. The system peaked overnight and easterly ridgetop winds averaged in the 40’s mph with gusts in the 70’s. Snowfall totals as of 6am are 12-20″ in Girdwood and 6-10″ at Turnagain Pass. The rain/snow line has been around sea level to 300′.

Today:  The storm is forecast to taper off before noon with an additional 1-3″ of snowfall in the morning hours. Ridgetop winds look to slowly decline as well from the 15-25mph range, where they are this morning, to 5-10mph from the east. Skies should remain mostly cloudy with some partial clearing late in the day. Temperatures look to remain in the mid 30’sF at the lower elevations and near 20F along the ridgelines.

Tomorrow:  Another round of storms heads in tomorrow afternoon and should extend through the week. This event looks to be more potent and a bit wetter by Thursday into Friday. Stay tuned as this active pattern continues.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30 5 0.6 96
Summit Lake (1400′) 28 3 0.2 46
Alyeska Mid (1700′) 29 14 1.4 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21 NE 28 75
Seattle Ridge (2400′) 23 SE 20 41
Observations
Recent Observations for Turnagain Pass
Date Region Location
05/11/22 Turnagain Avalanche: Cornbiscuit and Magnum west faces
05/07/22 Turnagain Observation: Granddaddy
04/29/22 Turnagain Observation: Sunburst wx station
04/28/22 Turnagain Observation: More Turnagain Pass/Summit Lake wet slab activity
04/27/22 Turnagain Observation: Magnum
04/27/22 Turnagain Observation: Girdwood/Summit/Turnagain Road obs
04/24/22 Turnagain Avalanche: Seattle Ridge – large glide avalanche on Repeat Offender path
04/24/22 Turnagain Avalanche: Seattle Ridge uptrack
04/24/22 Turnagain Observation: Pastoral
04/24/22 Turnagain Observation: Sunburst
Riding Areas
Updated Fri, May 13th, 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
Open
Open. Extended opening through May 31.
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.

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.