Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, February 25th, 2019 - 7:00AM
Expires
Tue, February 26th, 2019 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is  MODERATE  on slopes over 35 degrees above 2,000′. Triggering a slab resting on weak faceted snow is still possible. Slabs could be anywhere from 6″ to 2′ thick depending on prior wind-loading. Additionally, pay attention to changing conditions with warm temperatures in the Alpine, especially on steep slopes in direct sunshine. As always, give cornices a wide berth and limit exposure under glide cracks.

SUMMIT LAKE / JOHNSON PASS:    Triggering a larger, more dangerous slab remains a concern due to  variety of old weak layers in the mid and base of the snowpack. Extra caution is advised. Evaluate snow and terrain carefully.  

SEWARD / LOST LAKE:   Slabs up to 2′ in depth could be found and triggered in this area on steep wind-loaded slopes.

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Mon, February 25th, 2019
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
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

With a strong inversion in place some Alpine weather stations are already near or above freezing this morning. Alyeska Summit (3664′) is at 35F and the base of Alyeska (100′) is at 13F. Sunburst (3812′) is at 30F and Turnagain Pass DOT (1020′) is at 7F. Summit Lake MP 45 (3800′) is at 36F and Summit Lake DOT (1348′) is at 4F.  This is the first day to see temperatures above freezing at upper elevations. It will be important to pay attention to changing conditions. This can sometimes make triggering an avalanche on a persistent weak layer more likely. Be most suspect on steep slopes getting direct sunshine. Look for roller balls and wet sluffs, signs that the snow is heating up. The slab avalanche issues today revolve around older weak layers within the snowpack (persistent weak layers). The most recent weak layer (the Valentine’s near surface facets) sits around a foot deep under the wind affected snow and old wind slabs. This layer has been showing signs that it could still be reactive if you find the trigger point. There was a small skier triggered avalanche observed yesterday looker’s right of Ragged Bowl (near Girdwood) that is suspected to have run on this layer. The second layer down is the MLK Jr buried surface hoar. Although found throughout the advisory area this layer is showing signs of only being reactive in the Summit Lake zone. Additionally in the Summit Lake region there is weak snow near the ground. 

If you are headed out today watch for:
    –  Wind-loaded, steep, unsupported slopes are the most suspect for popping out a wind slab that may be sitting on weak snow.
    –  Larger and more dangerous avalanches are possible in the Summit Lake and Johnson/Bench peak area where a thinner snowpack exists.
    –  SUN EFFECT and moist/wet sluffs on steep rocky southerly terrain. 
    –  Cornices. Warmer temperatures at higher elevations can help loosen these monsters and with good weather and ridgeline travel, don’t forget to give cornices a wide berth.
 And remember to practice safe travel protocol

Observer on Max’s yesterday found no signs of instability but found the buried Valentine’s facets to still be reactive, 2.24.19

 

Large natural avalanches triggered by high winds on 2.21.19 in Summit Lake. If heading that way remember the snowpack is harboring a number of weak layers. 

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

Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time.  The best way to manage this problem is to avoid traveling on slopes directly below glide cracks. A short list of known cracks in popular zones:  Magnum, Lipps, Seattle Ridge, Eddies, Lynx Ck. See a new glide crack or one that appears to be opening up? Please snap a photo and send us a quick ob!

Weather
Mon, February 25th, 2019

Yesterday: Mostly sunny with some high clouds, very light westerly winds and temperatures in the 20Fs in mid to upper elevations. Overnight valley bottoms saw temperatures in the single digits with the inversion in place.  

Today: Mostly sunny with a chance of valley fog in the morning. Light winds. With the temperature inversion early morning temperatures in the Alpine are near or above freezing and valley bottoms are in the teens to single digits. Valley bottoms temperatures are forecast to rise into the 20Fs and then dip back down overnight. Upper elevations should stay in the 30Fs to high 20Fs.  

Tomorrow: The ridge of high pressure looks to dominate the weather pattern and similar weather looks to be on tap for the remainder of the week with the high temperatures slightly increasing each day and lows in the teens at night in the valley bottoms.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 23   0   0   61  
Summit Lake (1400′)  12     0   0   29  
Alyeska Mid (1700′) 24    0      0      56    

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  24  SW 3   9  
Seattle Ridge (2400′)  24   NW    1      6    
Observations
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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
Closed.
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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