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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
Wed, December 24th, 2014 - 7:00AM
Expires
Thu, December 25th, 2014 - 7:00AM
Forecaster
CNFAIC Staff
The Bottom Line

Today the danger rating above treeline is MODERATE. The likelihood of triggering a 1-3′ slab avalanche is possible above 2500′ and could have high consequences. These slabs are most likely to be triggered on steep slopes where the snowpack is thinner. Ridgetop winds are expected to increase with a possible accumulation of 3-5″.   Small, isolated wind slabs up to 8″ in depth on leeward slopes are also a concern for today.   Identify steep terrain, evaluate the snowpack carefully and watch for people above and below you.

The danger rating for treeline is at LOW today and human triggered avalanches below 2500′ are unlikely. It is possible for an avalanche triggered from above to run into this elevation band, therefore be aware of skiers on slopes above you and travel one at a time under steep terrain.

There is No Rating below 1000′ due to insufficient snow coverage.

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Wed, December 24th, 2014
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

The primary concern today is a one-week old slab (1 – 3’ deep) sitting on a layer of buried surface hoar. Buried surface hoar has been found over the past week throughout Turnagain Pass and Summit Lake above 2000’ on all aspects. This particular combination of weak layer plus slab is known to linger for long periods of time and explains why we are still getting some moderate to hard results in our test pits when we isolate the weak layer. No new signs of obvious instability have been reported since the Sunburst avalanche that buried one skier on December 18th.  This leads us to believe that the weak layer is adjusting to its new load and the overall stability of the snowpack is gradually improving.

The weather forecast today is calling for 3-5″ of new snow throughout the day with moderate winds. This new load will contribute to our primary concern by placing additional stress on the weak layer. 

It’s important to realize a MODERATE rating refers mainly to the likelihood of initiating an avalanche and does not take consequences into consideration.  If you were to find just the right trigger point to initiate an avalanche it could propagate across the entire slope, making escape difficult at best.  Because of this we are on the higher risk side of the moderate scale. 

Persistent slabs are most likely to be triggered on steep slopes in thinner areas of the snowpack.  We are advising backcountry users to be smart about terrain choices and to think about the consequences before deciding to ski a steep slope. Take the time to evaluate the terrain and avoid steep slopes with convex rollovers or shallow areas around rocks.  

 

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

Ridgetop winds are expected to be moderate with gusts into the mid twenties today. We have an existing 5 inches of low density snow available for transport and are expected to recieve another 3-5″ throughout the day. This is just enough wind and snow to form isolated wind slabs up to 8″ deep on leeward aspects.  Terrain features such as ridges, gullies and convex rollovers will be the most likely places to encounter these newly formed pockets of slab. These slabs are expected to be small and isolated, but if caught off guard could be enough to knock you off your feet.  Pay attention to the consequences below and look for obvious signs like shooting cracks, hollow sounds, or smooth pillowy looking features.   

Weather
Wed, December 24th, 2014

Yesterday skies were clear; winds were calm, and temperatures were in the 20’s F.

Overnight winds remained calm, temperatures dipped into the teens, and no precipitation was recorded.

Today temperatures are expected to remain in the high 20’s F at 1,000′ and 3-5 € of snow is forecasted for today.  Ridgetop winds are expected to increase to 15-25 mph out of the East.

Another 3-6 € of snow is expected tonight and could continue through Christmas day. Temperatures are expected to stay in the 20’s F with highs in the low 30’s F near sea level. Winds are expected to remain moderate throughout the evening.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 24 0  0 29
Summit Lake (1400′) 15 0  0 4
Alyeska Mid (1700′) 25 0  0 21

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  21  E 5 24
Seattle Ridge (2400′)  22  N/A  N/A N/A
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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

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
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.