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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, February 5th, 2013 - 7:00AM
Expires
Wed, February 6th, 2013 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

There is a MODERATE avalanche danger today for wind slab avalanches above treeline. Moderate to strong east winds over the past few days have loaded slopes that will be possible to trigger 1-2′ deep. These are most pronounced near ridgelines, on rollovers and cross loaded in gullies. With clearing skies allowing for travel into more complex terrain, it will be a day to think about consequences. Where will you end up if you kick off, and cannot manage, one of these slabs? Below treeline there is a LOW danger where several crusts are tying the snowpack together.

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Tue, February 5th, 2013
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
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.
More info at Avalanche.org

There were a couple very small skier triggered wind slab avalanches yesterday on freshly wind loaded rollovers/wind lips near treeline. One natural wind slab, a bit bigger (30-40’ across, ~1′ deep and running around 150’), was seen in a cross-loaded gully on the east face of Seattle Ridge (looker’s left of the motorized “up-track”). Keep in mind, the low visibility kept folks to the mid and lower elevations leaving the upper, and more concerning, slopes untouched.

Today, triggering a lingering wind slab will be the primany concern. The wind has backed off considerably this morning but it did load its fair share of slopes over the past several days. These slabs are most likely to be 1-2 feet in depth and found just off ridgelines, rollovers and cross-loaded in gullies. Watching for smooth “pillowy” surfaces, hollow feeling snow and cracking in the snow around you will be keys to recognizing these slabs. With the potential for good visibility today and travel to steeper slopes, even a small avalanche triggered can be dangerous if one gets washed into a terrain trap (i.e., over a cliff or into a gully).

Cornices:  With several days now of warm temperatures, snow and wind, cornices have been building. Giving these monsters a wide berth will be prudent as they could be close to the tipping point.

Below treeline:  It will be unlikely to trigger an avalanche below treeline. A few inches of low density snow sits on multiple crust layers that extend up to 2,000’-2,500’. The most recent crust was formed February 2nd and is somewhat breakable with a stouter rain crust from 1/30 below.

Avalanche Problem 2
  • 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

Ah, the deep slab problem… Yes, it has been 3 weeks now since the last deep slab avalanche and yes, it would be nice to put this broken record away, but time will tell. We have been tracking the weak October and November facets at different elevation bands the past couple days. These are buried 4-7’ deep in general and continue to show gains in strength. Reports from the 2,400′ and 3,000’ band show the facets remain dry and intact but are rounding, bonding and gaining in hardness. This is all good news and what we want – but these pits are only small snapshots. Due to the severity of this type of avalanche, and the rule that facets can come back to bite one, it is a guilty untill proven innocent situation. In the mean time, steering clear of thin spots, exposing only one person at a time and moving efficiently through avalanche terrain are good practices.

Weather
Tue, February 5th, 2013

Over the past 24 hours we have seen a trace to an inch of new snow with moderate to strong easterly wind. Skies have been overcast and temperatures mild, in the 30’s below treeline and mid 20’s on the ridgetops.

Today we should see a break in precipitation, wind and cloud cover. The sun is even on tap to make an appearance. Wind has backed off and barely blowing, in the 0-10mph range, from the east where it should remain light but shift to the northwest during the day. Temperatures look to remain in the low 30’s at 1,000′ and mid 20’s on the ridgetops.

Tomorrow looks like clouds will head this way again as the next system pushes in from the southwest for another shot of precip on Thursday.


 Kevin will issue the next advisory tomorrow morning, February 6th.

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Riding Areas
Updated Mon, October 26th, 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

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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.