Turnagain Pass RSS

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Tue, December 12th, 2017 - 7:00AM
Wed, December 13th, 2017 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

The  avalanche danger is HIGH  due to continued heavy rain, wet snowfall and strong winds.  A very potent warm and wet storm has saturated the snowpack and caused a natural wet avalanche cycle below 3000′. Today natural and human triggered wet slab avalanches are likely at Treeline and storm snow avalanches are likely in the Alpine. Today is a good day not to go into the mountains.  Travel in avalanche terrain is NOT recommended.  

Below 1,000′, where little snow exists, there is a  CONSIDERABLE  avalanche danger for debris running into steep or channeled terrain.

**Summit Lake also has elevated avalanche danger and the weekly summary can be found HERE.

Special Announcements

Elevated avalanche danger remains throughout Southcentral, AK due to continued stormy weather. If you are headed to Hatcher Pass check out hpavalanche.org and for Valdez, valdezavalanchecenter.org  Also, there have been reports of unstable snow and human/natural triggered avalanches near Petersville and  the Dutch Hills  area.

Tue, December 12th, 2017
Above 2,500'
4 - High
Avalanche risk
4 - High
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

A series of warm and wet storms have created a widespread avalanche cycle across our forecast zone. Over the last three days 3.1 inches of rain has saturated the mid elevations (treeline zone) and rain/snow line has fluctuated between 2000’ and 3000’. A brief window of good visibility yesterday allowed for a look around Turnagain Pass where dozens of recent wet slab avalanches have occurred on all aspects below 3000’. These avalanches have been releasing near the ground on a well documented weak layer of faceted snow. The most interesting (and scary) avalanches observed yesterday were on the West facing terrain of Tincan below 2500’, an area many folks go when the avalanche danger is elevated. This avalanche cycle speaks to the powerful nature of a saturated snowpack and is a reminder that even small terrain features are suspect. An avalanche of this kind, if triggering from below or in a terrain trap, would be unsurvivable. Today another .5” of rain is expected below 2000’ combined with moderate to strong Easterly winds. High avalanche danger will continue through today and will remain elevated until the snowpack has a chance to drain or freeze. Travel in avalanche terrain is not recommended. 

Recent wet slab avalanches were observed yesterday afternoon on the West facing terrain of Tincan. 


 Recent avalanches on Northern and Western aspects of Corn Biscuit.


Dozens of slabs have ripped out to the ground on the SE face of Seattle Ridge and most of the gullies are filled with debris. As of yesterday the uptrack on Repeat Offender remained intact. 

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

In the Alpine, wet and heavy snow is falling, which becomes drier with elevation. From our rainfall totals at the snow stations over the last three days, we can expect around 3’ of snow has accumulated in the alpine. Cornices are building and the weak pre-existing snowpack continues to be loaded. Storm snow avalanches that include storm slabs, wind slabs and cornice breaks all can be expected today at the high elevations. This snow may also overload and tip the balance of the weak snow sitting near the ground and create a very large avalanche, taking most of the snowpack with it. This size avalanche could run into the lower elevations in steep or channelled terrain.  

Again, the message is simple for today, avoid avalanche terrain. This means steering clear of all slopes 30 degrees and steeper including your exposure to runout zones.

Tue, December 12th, 2017

Yesterday another 0.5 € of rain fell in Turnagain Pass and .94 € of rain Girdwood. Temperatures remained above freezing, mid 40F’s at seal level and mid 30F’s at 1000′. Easterly ridge top winds averaged in the 20’s with gusts in the 60’s. Temps cooled briefly last night bringing snow/rain line to 1700′ where a few inches of wet snow has accumulated at mid elevation weather stations.  

Today another 0.5 € of rain is expected throughout the day and rain/snow line is expected to be around 2000′. Easterly ridge top winds could range from 20-30mph with gusts in the 40’s. Tonight continued rain showers are expected.  

Stormy weather in the form of rain showers and strong Easterly winds is anticipated through Wednesday afternoon. Winds should diminish tomorrow afternoon and temperature will gradually start falling. Thursday into Friday we may see freezing temperatures again at sea level with a possibility of scattered rain and snow showers.  

*Center Ridge snow depth at 6am is estimated due to depth guage sensor experiencing noise.

** Sunburst weather station data is from 6am – 8pm (12/11/17) due loss of battery power yesterday evening.    

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 34    3 0.5   *28  
Summit Lake (1400′) 34    0 0.1   9
Alyeska Mid (1700′) 35   2   .94   16  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) **26   **ENE   **28 **62  
Seattle Ridge (2400′) 30   ESE    21 50  
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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.