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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, March 12th, 2013 - 7:00AM
Expires
Wed, March 13th, 2013 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The majority of terrain in the mountains of the Eastern Turnagain Arm has a LOW avalanche danger. However, pockets of MODERATE danger do exist for cornice falls and loose snow avalanches. Cornices are large, potentially unstable and should be avoided from both above and below.   Human triggered dry loose snow avalanches on steep shady slopes should be expected. Additionally, in areas the winds are calm enough to allow the surface crusts on south aspects to warm with today’s sunshine, damp/wet snow sluffs are possible.

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Tue, March 12th, 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
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Cornice falls will be our primary concern. These behemoths have the potential to break on their own as well as with the added weight of a person/people. They are by far the most dangerous avalanche issue right now as they could fall in bus sized (or bigger) masses and tumble to valley bottoms. Add to that the large amounts of snow that can be entrained, or avalanches triggered, along the way and a quiet day in backcountry can quickly change. We have had a handful of these calve off during the past 2 weeks, with the most recent sometime around Saturday March, 9th – as seen in the photo below.

Predicting cornice failure is very challenging, but intense sun with calm wind increases the likelihood. Giving these guys a wide berth is necessary while traveling on ridgelines as well as underneath them. This includes being mindful of any place you stop – for example, to eat lunch, watch your buddies hill climb or put on your skins.

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Loose snow avalanches (a.k.a. sluffs) should be fairly easy to initiate today on slopes 40 degrees and steeper. This was the most common issue yesterday. These will come in the form of:

Dry snow – Fast moving but fairly low volume sluffs can be expected on steep shady aspects. With our cold temperatures, shady slopes are becoming looser by the day as the surface snow is faceting.

Wet/damp snow – Southerly aspects will have a crust this morning that might bake down with today’s sunshine and become soft by the afternoon. Light to moderate winds are on tap however and may limit warming of the surface. If crusts do soften expect slow moving damp/wet sluffs to occur. The steeper and more sustained the slope the higher volume and more concerning the sluff. These easily avoidable avalanches can quickly get out of hand in the right terrain where they can pile heavy snow up in gullies quickly for example.

Additional Concerns:
Wind slabs:  North and easterly winds approaching 20mph are possible in scattered areas today. It will be good to keep an eye out for both any fresh slabs formed by this slight bump in wind or old stubborn wind slabs from last week’s high wind event. Any wind slab issue is likely to be confined to the steep “extreme” terrain.

 

Surface conditions:
Surface conditions are exceedingly aspect dependent (it is March after all).  The northern half of the compass sports mostly soft settled powder with varying degrees of stiffer wind effected snow just below the surface.  The southern half consists mainly of sun crusts. Surface hoar now covers all of these aspects above treeline and is a potential future problem when buried by the next snowfall.

Weather
Tue, March 12th, 2013

Sunny skies prevailed in most areas yesterday with a few low lying clouds. Temperatures rose to the mid 20’sF on the ridgetops and mid 30’s at sea level. Winds were light from the northwest ~5mph.

Today, intense sun with a cool breeze is in the forecast. Skies are clear this morning and temperatures overnight have dropped to the teens across the board €“ low teens at sea level and mid teens on the ridgelines. Winds early this morning have shifted NE and bumped up slightly to the 10mph range with gusts to 20mph. Through the course of the day, temperature should rise to the low to mid 20’sF on the ridges and 30’s at sea level. Ridgetop winds are forecast to remain around 10-15mph from a northeasterly direction.

The high pressure centered over the Bering looks to remain through tomorrow with the associated clear skies over our area. Thursday a low pressure moves in from the Gulf bringing a chance for flurries and partly cloudy skies.


Kevin will issue the next advisory tomorrow morning, March 13th.

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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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Turnagain Pass
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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.