Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 6th, 2017 - 7:00AM
Expires
Sat, January 7th, 2017 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A MODERATE avalanche danger exists on steep terrain above the trees where winds have loaded slopes. Although the very strong winds have blown much of the snow away, expect to find shallow wind slabs that formed off ridgelines and lower on slopes. Watch for any steep slope that harbors recent wind deposited snow. Additionally, these wind slabs may overload buried weak layers and triggering a larger and more dangerous hard slab avalanche exists.  

Lower elevations that have escaped the winds, along with upper elevation slopes that are wind scoured, have a  LOW avalanche danger where triggering an avalanche in unlikely.

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Fri, January 6th, 2017
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

Very strong “outflow” winds impacted the region yesterday. Cold arctic air rushing down from the North battered the mountains. What soft snow did remain after the Dec 30th wind event was likely taken away with this Jan 5th wind event – a bit like salt on the wound! We only know of one small natural wind slab that released on an Easterly aspect in the Summit Lake area yesterday. Otherwise, there was just too little snow available for transport to produce natural wind slab avalanches. 

For Today:  Watch for new wind slabs from yesterday, overnight and today (winds are forecast to be moderate from the North and West). These slabs are likely to be shallow, very stiff and could surprise you on a steep slope. Watch for these in any location with wind loading, including lower on slopes. These also have the potential to overload buried weak layers and produce a much larger and dangerous avalanche. The Easterly face of Seattle Ridge is an example of where winds have been loading and known buried weak layers exist.

Safe travel protocol is your friend and if you head out today, remember to expose one person at a time, watch your partners, have an escape route planned and group up in safe zones.

 

Significant wind transport along Wolverine Ridge (seen from Portage). Winds along this ridge were more Southwesterly due to “terrain forced flow” in complex topography. 

 

The Summit Lake and Kenai Mountains got hit as well with these impressive winds. Below are plumes coming off the Southwest shoulder of Silvertip Peak (far left). 

 

Avalanche Problem 2
  • 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

Although the snowpack is wind hardened and tired, it does have a poor structure. There are a variety of weak layers in the middle of the pack as well as at the bottom. The slab on these weak layers is quite variable and hard – and though difficult to trigger, the possibility does exist. Steep wind loaded slopes (Northern and Eastern) that haven’t avalanched yet are the most suspect. Likely trigger spots are in thinner areas near rocks. Obvious signs like cracking and ‘wumpfing’ are becoming less common, making it more difficult to assess slope stability. Heavier loads, such as snowmachines or large groups of people can also be a trigger. 

In the periphery areas (Girdwood, Johnson/Lynx Creek and Summit Lake) where a thinner snowpack exists, several observers have experienced collapsing/wumpfing in recent days. 

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Believe it or not, 3 glide avalanches have occurred in the past 5 days in the Turnagain Pass zone. These are SE aspect of Lynx CreekSE aspect of Seattle Creek, and the SW face of Eddies. Along with recognizing wind affected snow, keep an eye out for glide cracks and limit time under these. They can have a knack for releasing during cold weather.

Weather
Fri, January 6th, 2017

Extremely strong Northerly winds impacted the Southcentral mountains yesterday. Skies were mostly clear, but winds were averaging as high as 54mph with gusts to 79mph. These winds brought temperatures down to ~10F on the peaks but scoured out the cold air in the valleys where temperatures rose to the upper 20’sF.

Overnight we have seen decreasing winds, but we are still expecting the North flow to be moderate – averages 10-15mph with gusts into the 30-40’s. Temperatures should remain chilly, 10-15F at most elevations and valley bottoms. Skies look to be mostly clear today.

It seems as though the blocking area of high-pressure over mainland Alaska will persist into next week. Along with this will be clear skies, cold temperatures and no expected precipitation.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 19   0   0   35  
Summit Lake (1400′) 21   0   0   11  
Alyeska Mid (1700′) 20   0   0   23  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  12 NW   11   63  
Seattle Ridge (2400′)   16   N   38   79  
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Riding Areas
Updated Mon, December 02nd, 2019

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
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
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Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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