Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, January 4th, 2022 - 7:00AM
Expires
Wed, January 5th, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains MODERATE above 2,500′ on slopes that have been wind loaded by last weekend’s winds. Triggering a lingering wind slab, up to a foot thick, sitting on a slick crust will be possible. These slabs are scattered around the Alpine terrain and should be fairly easy to spot and could look like large wind drifts.

The danger is LOW below 2,500′ where triggering an avalanche is unlikely.

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Tue, January 4th, 2022
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Low (1)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • 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

Brrrr…. It’s a cold day out there… -10 to -20F in valley bottoms and just above 0F along ridgelines. The Granite Ck weather station near the Johnson Pass trailhead is reading the coldest this morning at -26F. The good news is the winds are calm. They have been relatively light from the north and east for just over a day now and should remain light and variable for the next several days.

Lingering wind slabs sitting on a crust are the main avalanche concerns for anyone headed out. We can expect them to be scattered about in the Alpine terrain. They formed when last weekend’s winds blew around 3-5″ of snow that fell on Friday. Slabs should be on the smaller side, from a few inches thick to possibly a foot. They could still be a bit touchy and run further than expected as they are sitting on a crust formed over the New Year. Watch for signs of wind deposited snow and cracking in the snow around you.

Example of that darn crust at the higher elevations. These sluffs were likely triggered by the winds over last weekend. Photo taken Sunday, 1.2.21.

 

On steep slopes with enough loose snow sitting on the crust, it may be easy to initiate a shallow sluff. These could also run further than expected but should remain small with the meager snow amounts available in general. That said, the New Year’s crust is creating some challenging travel conditions right now. The crust is quite variable in thickness (.5 – 1.5″ thick) and can be breakable in one place only to be stout and unbreakable in another. It’s covered by a few inches of windblown snow where it hasn’t been scoured or loaded. We found it all the way to 4,000′ in the Placer Valley area, which matches observations elsewhere, and as John said yesterday, we suspect it to extend to most ridgetops.

How the surface conditions evolve this week will be important in anticipation of the next snowfall. The New Year’s crust and any weak snow that sits on top of it will be a big factor in how well the next layer of new snow bonds, or doesn’t bond. Avalanche conditions could get quite interesting once the snow starts falling again, which could be this weekend.

Looks good from afar, but far from good…! Looking south over Squirrel Flats and Comet Peak on the left. Snow conditions were 4-5″ of loose snow over a breakable crust all the way to 4,000′. 

Additional Concern
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

We are continuing to track the layer of November facets that sit 2-5+ feet deep in the snowpack. This layer is most pronounced in the mid elevations where the old Halloween crust exists under the facets. The facets are continuing to show signs of hardening and bonding and the slab on top is now capped with the New Year’s crust. Although triggering an avalanche in this layer is very unlikely, it’s always good to keep an eye on buried faceted snow.

Weather
Tue, January 4th, 2022

Yesterday:  Clear skies and cold weather were over the region. Temperatures in valley bottoms were in the minus single digits and near 0F along ridgelines. Winds were generally light from the east along ridgetops.

Today:  Another clear and cold day is on tap. Valley bottoms temperatures are between -10 and -20F and have hit -24F at the Johnson Pass trailhead. Ridgetop temperatures are closer to 5-10F above as an inversion is in place. Winds are forecast to remain light from the east along ridgelines.

Tomorrow:  Clear and cold weather along with light winds should continue through the week. Weather models are hinting at what looks like a chance for snow and warmer temperatures this weekend. Stay tuned.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) -6 0 0 65
Summit Lake (1400′) -14 0 0 23
Alyeska Mid (1700′) -3 0 0 39

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 0 E 5 12
Seattle Ridge (2400′) -4 var 2 6
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Riding Areas
Updated Wed, December 01st, 2021

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
Open as of Dec 1st.
Placer River
Open
Open as of Dec 1st. Limited parking due to Portage curve construction.
Skookum Drainage
Open
Open as of Dec 1st. Limited parking due to Portage curve construction.
Turnagain Pass
Open
Open as of Saturday, Nov 27. Be aware of early season hazards (alders/creeks) and open water.
Twentymile
Open
Open as of Dec 1st.
Seward District
Carter Lake
Open
Open as of Dec 1st.
Lost Lake Trail
Open
Open as of Dec 1st.
Primrose Trail
Open
Open as of Dec 1st.
Resurrection Pass Trail
Open
Open as of Dec 1st.
Snug Harbor
Open
Open as of Dec 1st.
South Fork Snow River Corridor
Open
Open as of Dec 1st.
Summit Lake
Open
Open as of Dec 1st.

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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.