Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, December 22nd, 2014 - 7:00AM
Expires
Tue, December 23rd, 2014 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Today the avalanche danger above treeline remains at  CONSIDERABLE. Human triggered slab avalanches 1-3+’ deep are likely in steep terrain above 2500′. These have the potential to propagate across entire slopes. An avalanche of this size could have very high consequences. You will be more likely to trigger an avalanche in areas where the snowpack is thin or on features like steep rollovers or near rocks.  Conservative decision-making and careful snowpack evaluation is essential today if choosing to venture onto steep slopes.  

The avalanche danger at treeline (2000 €“ 2500′) is MODERATE. The likelihood of human triggered avalanches is possible at this elevation, but it’s more likely that an avalanche triggered above could run into this zone. Identify steep slopes above and practice safe travel techniques.  

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Mon, December 22nd, 2014
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
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

A short burst of snowfall yesterday morning added a welcome 5-9″ of very low density snow in the Girdwood Valley and 1-4″ at Turnagain Pass. With the chance for a few more inches of light snow today, this will add to the soft surface conditions, but the avalanche concerns will remain deeper in the pack.

The primary concern continues to be a slab (1 – 3+’ deep) sitting on a layer of intact buried surface hoar. Last week this combination (slab + weak layer) was very touchy causing several large human triggered avalanches including a full burial in Turnagain Pass. As this layer has had time to adjust we have noticed it gaining strength and getting harder to trigger in our test pits. Check out this VIDEO from yesterday. Unfortunately, when it does collapse there is a lot of potential to propagate over an entire slope. In other words, the probability of triggering a large avalanche is decreasing, but due to its thickness and potential to propagate, the consequences are high.

In the right type of terrain you might trigger an avalanche or you might not. Many people could ski the same steep slope before someone hits the right trigger spot. It can be nearly impossible to know the exact location of these areas, but a good rule of thumb is to avoid thin snowpack areas, steep convex rollovers and areas near rocks. If you find yourself creeping into steeper terrain be aware of the consequences below you. It can be easy to assume that just because a slope has been skied it is deemed “safe.” 

There is a lot of uncertainty around this avalanche problem. We haven’t received any reports of recent avalanche activity in the last few days. Our observations have been limited to our roadside access on low consequence terrain of Tincan, Sunburst, and Seattle Ridge.  We have only been able to investigate this slab plus weak layer combination on slopes below 35° in Turnagain Pass. We don’t know how reactive this weak layer is south of Sunburst or in elevations higher than 3400’. Girdwood received the highest amount of precipitation from the Dec.14-17th storm and this slab layer gets gradually thinner as you head south through Turnagain Arm. We know that the Summit Lake area has the shallowest snowpack, and we suspect it could be easier to trigger a persistent slab in this region. 

 

Weather
Mon, December 22nd, 2014

Yesterday morning Turnagain Pass received 1-4 € of low-density snow and 5-9 € fell in the Girdwood Valley. Winds were light from the East with temperatures in the mid to high 20’s F.  

Overnight there has been no new precipitation recorded. Winds were calm and temperatures have increased to 32 °F at sea level and the mid 20’s F on the ridgetops.

There is a chance we could see up to 4-6 € of low density snow at higher elevations today with very light and variable wind. This may be in the form of rain at sea level as temps are supposed to stay in low 30’s F.

Over the next few days, showery conditions are expected in the Western Prince William Sound area and could bring short bursts of snow to Girdwood and Turnagain Arm. Unfortunately, the forecast has a lot uncertainty and these small bands of moisture could miss us. Temperatures are expected to remain in the high 20’s F to low 30’s F at 1,000′ with light and variable ridgetop winds.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30   2   0.1 28  
Summit Lake (1400′) 28   0    0 4  
Alyeska Mid (1700′) 31   4   0.43   21

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25   E   7   20  
Seattle Ridge (2400′) 27    ]N/A N/A   N/A  
Observations
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Riding Areas
Updated Thu, April 01st, 2021

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
Open
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Summit Lake
Open

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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.