Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, March 2nd, 2022 - 7:00AM
Expires
Thu, March 3rd, 2022 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is LOW at all elevations this morning and expected to rise to MODERATE at the high elevations (above 2,500′) later this afternoon. Increasing easterly winds through the day should begin to form small wind slabs on steep wind loaded slopes. Later this evening into tonight, light snowfall with the strong winds will continue to build wind slabs. Watching for active wind loading, giving cornices a wide berth and limiting any time under glide cracks are all recommended for today.

SILVERTIP / SUMMIT LAKE:  A thinner snowpack with buried weak layers exist to the south of Turnagain Pass and outside of the advisory area in Summit Lake. Although triggering an avalanche breaking in these deeper layers is unlikely, extra caution is still advised on steep wind loaded slopes.

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Wed, March 2nd, 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 (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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

After a surprise mostly sunny day yesterday, clouds are forecast to move in today ahead of the next series of stormy weather. Easterly ridgetop winds are already rising this morning and should be blowing 15-25mph with gusts in the 30’s by later this afternoon. Snowfall should begin this evening with 2-3″ possible by tomorrow morning (to sea level!) and another 2-3″ through the day tomorrow. Another, more powerful, system looks to arrive tomorrow night.

With a generally stable snowpack now, the main avalanche concern moving forward will be associated with today’s increasing winds. There is not much snow to transport so any wind slabs that are able to form will most likely be small and in the high elevations. Once the snow starts falling, wind slabs will get a bit larger. There is a new crop of surface hoar that has been forming over the past few days. We saw this on all aspects and elevations on Seattle Ridge yesterday, even on the ridgelines above 3,000′. It has also been reported region-wide by others over the weekend. It is a fairly small layer (2-5mm feathers) but sitting on hard surfaces in many places. Until proven otherwise, we have to assume any new snow or wind slab sitting on this layer won’t bond quickly in the coming days.

For today, paying attention to changing conditions will be important. If you are in an area the wind isn’t transporting snow, the danger will remain LOW. Normal caution avalanche issues will still be present however. These are cornice falls, dry sluffs on steep slopes, and lingering wind slabs in steep rocky terrain. As always, good habits, such as giving cornices a wide berth and being suspect of old wind slabs in steep exposed zones are good practices.

A new batch of surface hoar with some small near surface facets were found on old wind crusts and melt freeze crusts. Sorry – the camera really wanted to focus on John Sykes riding instead of the surface hoar… This photo is from the Seattle Creek drainage yesterday 3.1.22.

 

Surface hoar was also found on very hard snow that exists along the highly wind affected Seattle Ridge. 3.1.22. *Big shoutout to Alaska Mining and Diving Supply and BRP/SkiDoo for providing the avalanche center with a new ‘loaner’ snowmachine each season, which gets us into these motorized zones!*

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

On the far north and south corners of the forecast zone, and to the south in Summit Lake, we are keeping track of old faceted layers that sit near crusts from Halloween and New Year’s. Although these layers are unlikely for a person to trigger, they could become active again with the next strong storm. The system coming in on Friday may not be strong enough to overload these layers, yet this is something we will be watching. In case you missed it yesterday, take a look at this report from Summit Lake that is outside of the advisory area – HERE.

Another additional concern are glide cracks.  A few more glide cracks have been noticed around the region. Be sure to keep an eye out for them and limit time under them. They can release unpredictably into a glide avalanche at anytime.

Glide crack, looking west from the Seattle Ridge weather station in the small drainage between 1st and 2nd Bowl. The crack looks to have stopped opening due to the old snow still covering up the ground. 3.1.22.

Weather
Wed, March 2nd, 2022

Yesterday:  Mostly sunny, to partly cloudy, skies were over the region yesterday. Ridgetop winds were light from the east. Temperatures were in the 20’sF at the higher elevations and in the mid 30’sF at lower elevations.

Today:  Mostly cloudy skies are forecast today with light snowfall beginning this evening. By tomorrow morning 2-3″ of new snow is forecast to sea level. Ridgetop winds will be slowing rising through today and blowing 15-25mph by this evening with stronger gusts. Temperatures should remain just under freezing at lower elevations and in the 20’s at the higher elevations.

Tomorrow:  Light snow with moderate to strong east winds will continue through tomorrow as this next system passes through. Around 2-3″ of snow is forecast to fall through the day. Another round of snow is headed in for Friday. Stay tuned.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 0 0 92
Summit Lake (1400′) 22 0 0 41
Alyeska Mid (1700′) 29 0 0 N/A

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 E 7 23
Seattle Ridge (2400′) 24 SE 5 11
Observations
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Riding Areas
Updated Sun, November 27th, 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
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass
Closed
The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail
Closed
Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake
Closed
Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.

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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.