Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 2nd, 2021 - 7:00AM
Expires
Sun, January 3rd, 2021 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains MODERATE on slopes over 35° above 1,000′. Today is another day to watch for lingering wind slabs in steep terrain, cornice falls along ridgelines and keep an eye on your sluff. Additionally, at elevations between 1,000′ and 2,500′ there is a small chance of triggering a large avalanche (3-5′ deep) on weak snow developing near a crust.

The avalanche danger is LOW below 1,000′.

SUMMIT LAKE: In addition to the avalanche issues mentioned above, there is still an unlikely chance a person could trigger an avalanche breaking near the ground above 2500′.

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Sat, January 2nd, 2021
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
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
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

One human triggered wind slab was reported on the SW face of Grandaddy Pk (head of Spokane Ck) yesterday. This slab was around 30′ wide, 8″ thick and ran around 300′. Skier was not caught. It was reported to have moved fast and though on the smaller side, was big enough to catch and carry a person.

Also yesterday, a group on the lower west ridge of Kickstep (upper Lyon Ck) triggered a cornice fall around 20′ wide. No one was caught. The party noted several cracks in the snowpack along the ridge where the cornices were peeling away.

Photo by Connor Johnson of the wind slab on SW face of Grandaddy Peak taken from Pete’s North. 1.1.21.

Cornice fall triggered by group along the lower west Kickstep ridge. 1.1.21. Photo: Duncan Wright

Avalanche Problem 1
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

What a great few days of high pressure and quiet weather in the backcountry. And another blue sky day is on tap with light NW winds before some high clouds begin moving in tomorrow. Many folks have been out getting on all kinds of terrain and only a few instances of snow moving have been reported (a small wind slab and cornice fall mentioned above). To add to this, steep slopes are also seeing sluffs, which can be expected where loose snow exists.

In short, the Turnagain Pass forecast zone is trending to a ‘Normal Caution’ avalanche regime and LOW danger. However, there is a bit too much funny business surrounding the Dec 1st crust to write it off. This crust keeps slowly degrading and in some areas is changing into a faceted layer creating a facet/crust combination. It sits on all aspects at the mid elevations (1,000′-2,500′) and if you want to take your probe out or dig down to it, it’s generally between 3-5′ below the surface. It’s unlikely a person can trigger a large avalanche breaking on this layer, but on just the right slope in a thin area it’s not out of the question. A few thin zones in my mind are Silvertip/Twin Peaks, Lynx Creek and areas on the south end of the forecast zone to Summit Lake. Additionally, thin areas in the upper Girdwood Valley could be suspect. This kind of setup doesn’t happen that often but enough that we know it can take a solid snowpack and turn it around causing avalanche issues deep in the pack weeks after a crust is buried. Whether this will happen is still to be determined, however we want to be ready. What we can do is remember to be cautious and suspect of the mid-elevations, especially in those thinner snowpack areas.

To add to the hidden buried weak layers concerning us, we are still watching those old October facets at the bottom of the snowpack in the Summit Lake zone. This layer is from 2,500′ and above in the Alpine where the slab on top of the facets is hard and crust-free. Again, it’s unlikely a person would trigger a slab near the ground, but not out of the question in just the wrong thin spot.

Otherwise Normal Caution avalanche issues:

Wind slabs:  Watch for lingering wind slabs in steep terrain. Cracking in the snow around you and stiff snow over softer snow will be clues to look for. Even a small wind slab triggered in high consequence zones can cause a lot of grief if knocked off our feet. As always, keep a close eye on the surface conditions and know your escape routes if a small slab happens to break under you.

Cornice falls:  As was seen yesterday, these looming snow features can break off at any time. Give them a wide berth from above and limit time under them.

Sluffs:  Sluffs are getting larger by the day with the cold weather. Keep an eye on these in the steeps.

This all said- with another travel-friendly brilliant day in the backcountry, we need to remember our safe travel protocol and good habits. That’s exposing one person at a time, having escape routes planned, watching our partners and for other groups that may be out there.

An example of sluffs is steep terrain. Back bowls of Seattle Ridge. 1.1.20.

 

The gray line roughly in the middle of the snowpack is the Dec 1st crust. This pit was at 2100′ on Eddies Ridge and the crust here did not show signs of weakness- good sign yes, but this isn’t the case everywhere. 1.1.21. Photo: Eric Roberts

Weather
Sat, January 2nd, 2021

Yesterday:  Blue skies and light north and easterly winds were over the region yesterday. Temperatures were in the teens to single digits in valley bottoms while the mid and upper elevations were in the 20-25F range.

Today:  Another blue sky day is on tap for today with some valley fog near Turnagain Arm. Ridgetop winds are expected to 5-10mph from the northwest. The temperature inversion remains in place, with chilly single digit to teens in valley bottoms and right near 20F at the mid and upper elevations.

Tomorrow:  One more ‘mostly’ clear sky day is forecast for tomorrow before this brief period of high pressure gets pushed out. Ridgetop winds are expected to be light and easterly while temperatures remain chilly in the drainages and near 20F along the ridgelines. Beginning Monday we should start seeing the impacts from the record setting low pressure in the Bearing now. It looks to join with another low and moves into the Gulf bringing a chance for a snowy mid to late week.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 20 0 0 75
Summit Lake (1400′) 8 0 0 30
Alyeska Mid (1700′) 19 0 0 78

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) *N/A *N/A *N/A *N/A
Seattle Ridge (2400′) *N/A *N/A *N/A *N/A

*Weather stations not reporting due to New Year date change – will be back up on line shortly.

Observations
Recent Observations for Turnagain Pass
Date Region Location
04/19/21 Turnagain Avalanche: Triangle, Seattle creek
04/18/21 Turnagain Avalanche: Turnagain Pass Road Obs
04/18/21 Turnagain Observation: Seattle Ridge, approximately 300 yards south of the up track
04/17/21 Turnagain Avalanche: Road obs
04/16/21 Turnagain Avalanche: Seattle Ridge
04/16/21 Turnagain Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge
04/16/21 Turnagain Observation: Sunburst
04/15/21 Turnagain Observation: Tincan
04/13/21 Turnagain Observation: Turnagain Pass Road Obs
04/12/21 Turnagain Observation: Tincan
Riding Areas
Updated Thu, April 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
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Summit Lake
Open

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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.