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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
Sun, January 4th, 2015 - 7:00AM
Expires
Mon, January 5th, 2015 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger remains  MODERATE  in Alpine terrain (>2,500′) on steep slopes for hard slab avalanches breaking 1-3′ deep. Although an avalanche will be difficult to trigger, the potential is there that one could bury or injure a person.  

At the treeline elevations (1,000-2,500′) the danger is LOW  where triggering an avalanche is unlikely.

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Sun, January 4th, 2015
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
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
No Rating (0)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

As we roll into a several day period of high pressure and clear skies, don’t forget what is lurking below the surface. Roughly 2′ down (give or take a foot) are persistent weak layers that vary with region. Turnagain Pass is plagued with mainly buried surface hoar and in lower snowpack zones, such as the West side of Girdwood Valley and Summit Lake, varying degrees of a facet/crust combination also exist. Although the slab on top is very hard and dense, making it difficult for a person’s weight to impact these layers, they are still there, not buried all that deep and continue to show signs of reactivity in pits. 

I was with an Avalanche Level 2 Refresher course yesterday and we dug several pits in the lower Alpine zone (~3000′) focusing on the buried surface hoar. Test results were exactly what we saw a week ago – high strength (hard to trigger an avalanche) and high propagation propensity (if an avalanche is triggered, it has potential to propagate across an entire slope). Although time is on our side and the buried surface hoar has adjusted to its current load, it still doesn’t buy a ton of confidence.

A few things to remember with this type of Avalanche Problem:

  • Absence of red flags until it’s too late (whoomphing, collapsing, cracking)
  • Trigger points are often where the snowpack is thin (around rocks and steep rollovers)
  • Make sure your safe zones are truly safe, hard slabs can propagate wider than you may expect
  • Expose only one person at a time


Photos: Buried surface hoar that is laying 14-16″ deep at 3,100′ on Sunburst’s SW face (Ryan Davis).

Left photo, standing upright on the bottom of the slab.                  Right photo, laying on a 2mm grid (5-8mm in size)
  

Avalanche Problem 2
  • 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

Very hard and supportable wind slabs litter the mountainsides above treeline. These are generally 6-12″ thick and fairly well locked into place in many areas. However, there is still a possibility of triggering one in very steep and rocky terrain. Chances also go up if the slab is unsupported from below (i.e., is sitting above a cliff, steep rollover or a steep gully sidewall).

This also paints a picture of the current surface conditions in exposed, above treeline zones – hard and slick. Where stiff wind slabs are not present, scoured snow, rocks and anti-tracks are. Sounds a bit dire, yes, but there is fun riding to be had in sheltered areas in the trees as well as terrain depressions and the like.

Weather
Sun, January 4th, 2015

Mostly clear skies and light North winds greeted backcountry travelers yesterday. Temperatures were in the upper teens in valley bottoms and ~20F on the ridgetops. The last measureable precipitation was December 30th (the end of the very windy late December storm).  

Today, clear skies are on tap once again as a blocking high pressure has set in over mainland Alaska. A slight bump in Northerly winds (up to 10-15mph) are expected on the ridgetops. Temperatures are inverted this morning with valley bottoms in the single digits to low teens and the high teens to 20F on the ridgetops. We should see little warming through the day.

Our weather the next several days will be dominated by this blocking high pressure. Later in the week, there is a chance it could break down in the Southcentral coastal zones bringing some clouds and a chance for snow flurries. You can bet we will be watching the longer range weather models for the next storm.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21   0   0   34  
Summit Lake (1400′) 16   0   0   6  
Alyeska Mid (1700′) 19   0 0   25  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20   NW   4   13  
Seattle Ridge (2400′) 19   Variable   3   10
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Riding Areas
Updated Fri, May 01st, 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

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
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Carter Lake
Closed
Lost Lake Trail
Closed
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Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
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Closed

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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.