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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, February 26th, 2017 - 7:00AM
Expires
Mon, February 27th, 2017 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is  MODERATE  above 2,000′ in the Alpine where triggering a 2-3′ slab avalanche in steep terrain is still possible on all aspects. In addition, there are a handful of other avalanche concerns including shallow wind slabs, cornice falls, sluffs and glide avalanches.  

Below 2,000′ there is a  LOW  danger where triggering an avalanche is unlikely due to a snowpack consisting of hard crusts.

In Summit Lake, Girdwood, and on the southern end of Turnagain near Johnson Pass triggering a deeper more dangerous avalanche near the ground is still possible, but will be hard to trigger.

Check out the Saturday Summit Summary HERE.

 

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Sun, February 26th, 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
  • 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

Above 2000′ a widespread layer of buried surface hoar remains a concern on steep slopes, where triggering an avalanche 2-3’ deep is becoming tougher by the day as the snowpack slowly stabilizes and adjusts. Relatively calm weather this week has allowed for folks to push further into the mountains with no reports of avalanche activity since last Saturday (2/18). However, this weekend it is important remember that poor snowpack structure still exists and triggering a slab avalanche could have high consequences. 

Yesterday stability tests on the West face of Corn Biscuit were a bit alarming with propagation on the buried surface hoar layer as well as near the ground on basal facets. These kinds of stability results are confusing when you see dozens of people ski/ride steeper parts of the adjacent slope without incident. This is an example of the high level of uncertainty with this type of avalanche problem. Tipping the balanche may require a big trigger (snow machine or multiple people on a slope) hitting just the right trigger spot. Thinner areas of the snowpack in steep terrain near rock bands or scoured features are places to avoid. A helpful way to think about this problem is to consider the consequences of a slope if it slides and identify and avoid terrain traps (gullies, cliffs, or trees below). Be aware that obvious clues like “whumpfing” or recent avalanche activity are unlikely. 

Deep Persistent Slab: We continue to find various layers of weak faceted snow and depth hoar near the bottom of the pack in certain areas. This includes Summit Lake zone, and some areas in Girdwood Valley and towards the Southern end of Turnagain near Johnson Pass. Similar to the problem above, these layers will be very tough to trigger, but a possibility remains in places with this structure. 

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

Wind slabs: Loose surface snow and brief periods of moderate winds this week have formed shallow wind slabs in the alpine. Today expect ridge top wind to be in the 10-20mph range from the NW – this wind direction can funnel through some parts of Turnagain Pass from a Southerly direction. There remains plenty of snow available for transport and newly forming shallow wind slabs will be possible a variety of aspects. Watch for pillowed or drifted snow or where the snow may feel stiff and ”upside down.” Identify steep features like convexities or gullies where a shallow wind slab could knock you off our feet. Blowing snow and shooting cracks will be obvious clues to look for if the wind pick up today. 

Loose snow avalanches: The top 6” of surface snow is loose and sluffs may be easy to initiate and fast moving on steep terrain features protected from the winds. 

Cornices: Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

Glide avalanches: There is a new glide crack above the flats along Seattle Ridge, just looker’s left of the up-track and Repeat Offender slide path. Avoid hanging out under this crack and any others you may see – these release without warning and are very destructive.

Sunshine: Today skies may be partly sunny and solar warming may trigger loose snow avalanches in steep Southerly aspects. 

 

Large cornice on SW aspect of Magnum

 

Glide crack on Seattle Ridge has been slowly opening throughout the week

 

Weather
Sun, February 26th, 2017

Yesterday skies were sunning the morning with high clouds moving in late afternoon. Light Northwest ridge top winds (5-15mph) were observed yesterday and temperatures were in the mid to low 20F’s. Some low lying fog was present in parts of Turnagain Arm. Overnight NW winds bumped up into the 10-20mph range.  

Today skies are expected to become partly cloudy by the afternoon and temperatures will remain the 20F’s today. Northwest winds could range from 10-20mph. There is a chance of snow flurries in the morning.  

There is still some possibility for intermittent snow flurries in the next few days, but cooler temperatures are anticipated this week as a high pressure moves into the region. There is also talk of outflow winds by mid week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 26   0   0   66  
Summit Lake (1400′) 25   0   0   31  
Alyeska Mid (1700′) 27   0   0   61  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21   NW   7   24  
Seattle Ridge (2400′) 25    NNW 9   43  
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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
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Skookum Drainage
Closed
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Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
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Lost Lake Trail
Closed
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Primrose Trail
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Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
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South Fork Snow River Corridor
Closed
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Summit Lake
Closed
Closed.

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