Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, March 29th, 2018 - 7:00AM
Expires
Fri, March 30th, 2018 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger continues to be  MODERATE  above 1500′ on all aspects. Triggering a hard slab avalanche 2-4 feet thick remains a possibility and may be triggered remotely. Pay attention to afternoon warming and give cornices a wide berth.  

Similar avalanche concerns exist in the  Summit Lake area    and other zones on the Kenai.

 

Thanks to our sponsors!
Thu, March 29th, 2018
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
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
Moderate (2)
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
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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 little change in the weather and the days since avalanche activity increasing, the chances of triggering an avalanche are decreasing. The core Turnagain terrain is trending towards LOW hazard. However, we are still concerned about someone triggering a hard slab avalanche 2-4’ deep, especially in periphery areas like Girdwood and the South end of the pass towards Johnson and Lynx. The weak layers in the snowpack that formed in January will not just go away but over time can become “dormant”. The question is… are they? Without any big changes in the weather, these older layers (facets and buried surface hoar) are becoming more and more difficult to trigger and we are in a low probability, high consequence situation. The tricky part about this is, the pack appears to be stable but the chance remains for an unmanageable and destructive avalanche if a person hits just the wrong spot. No obvious signs of instability may be present before a slope releases and it may be the 10th skier or snowmachiner onto a slope that finds a trigger point. These trigger spots will be in thinner areas of the snowpack near rocks or in scoured areas along ridges. Although triggering a slab remotely is also becoming less likely with time, it is not out of the question with this snowpack structure. 

If the sun does shine today be aware of warming later in the day on Southerly slopes. 

Poor snowpack structure in Summit Lake. The concern is that the snowpack in the Southern end of the pass is very similar to this and a trigger spot may still be found.

 

It can be hard to remember that under all the hard wind affected snow and crusts there is a slab over buried weak layers. 

 

Additional Concern
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Many cornices are quite large. Temperatures have been cool lately but as we head into warmer, sunnier weather remember this can help de-stabilize them. As always, give cornices plenty of space and limit exposure underneath them.

Weather
Thu, March 29th, 2018

Yesterday was partly to mostly cloudy in the morning becoming overcast in the afternoon. There were a few snow showers. Temperatures were in the mid 20Fs to mid 30Fs. Winds were light and variable. Overnight skies were mostly cloudy and temperatures were in the 20Fs and winds remained light.

Today will be mostly to partly cloudy with a chance of snow showers. Temperatures will be in the 20Fs to low 30Fs. Northwest winds will be light. Tonight will be mostly cloudy with a continued chance of snow showers, temperatures in the 20Fs and light winds.

Tommorrow clouds decrease and skies clear for the weekend. As high pressure sets up there is an increased chance of outflow winds impacting the area. Clear and sunny looks to be the pattern into next week. Time to do some spring snow dances!  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  29  0  0  76
Summit Lake (1400′)  31  0  0  30
Alyeska Mid (1700′)  30  0  0  72

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  22  variable 5    15
Seattle Ridge (2400′)  27   variable  

 2    

 14
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
Riding Areas
Updated Wed, December 11th, 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.

Subscribe to Turnagain Pass
Avalanche Forecast by Email