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Thu, April 21st, 2016 - 7:00AM
Fri, April 22nd, 2016 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains  CONSIDERABLE  below 2500′ due to glide avalanches that are releasing daily in popular recreation areas. Avoidance is our best tactic right now: this means steering clear of being under the runout of glide cracks.  In addition, human triggered and natural wet loose avalanches are possible on steep southerly facing slopes with daytime warming.  

*In the Alpine where the avalanche danger is generally  LOW,  be aware of lingering wind slabs in steep terrain from Tuesday’s few inches of snow and wind (Girdwood Valley saw up to 10″). Also, shallow wet sluff in Tuesday’s snow is possible.

*ATTENTION HIKERS:  Summer use areas crossing under avalanche terrain should be avoided due to the possibility of natural avalanche activity. Byron trail in Portage Valley and Crow Pass are two examples of trails with dangerous avalanche terrain above.

AVALANCHE OUTLOOK for Friday, April 22nd:
For Friday we could see an increase in Easterly winds, a chance for light rain and a few inches of snow above 2,000′. Avalanche danger will likely remain LOW in the Alpine; unless precipitation amounts increase in which case shallow winds slabs and sluffs in the new snow would be possible. A CONSIDERABLE danger below 2500′ for glide avalanches will remain for Friday.

Special Announcements
  • Turnagain Pass advisories will be issued 4 days a week (Sat, Sun, Tues and Thur) until Saturday, April 30th when the Avalanche Center closes. For Summit Lake conditions, please see the  final  Summit Lake Summary and springtime tips  on this link.

  • Reminder: as the season winds down, we will continue to publish all reports/observations sent in. Don’t be shy – pass along what you see if you are getting out in the mountains!!
Thu, April 21st, 2016
Above 2,500'
1 - Low
Avalanche risk
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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. Dangerous avalanche conditions. 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
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Full-depth glide avalanches remain our primary concern as they continue to release daily. One new glide avalanche was noted yesterday in Turnagain Pass. This was on the West face of Magnum (yes, the glides are moving across the road…). On the Seattle Ridge side of the road there is not much snow left to slide; the exception being above the motorized up-track (photo below). Our message remains the same: AVOID TRAVEL UNDER GLIDE CRACKS. These are not ‘manageable’ avalanches and they are not triggered by people – travel among glide cracks can be done but not right now since they are releasing so consistently. 

Photo below: Glide avalanche in past 48 hours on the West face of Magnum. This is a POPULAR area to tour and there are other cracks near this avalanche that have yet to release. Avoiding this zone is recommended.


Photo below: The Seattle Ridge up-track seen yesterday, Wednesday, afternoon. No new glides have released in 4-5 days but that doesn’t mean one may release today. 

Avalanche Problem 2
  • 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 warm sunny day is forecast for today (Thursday) and with that means possible wet loose avalanche activity. Clear skies and cold temperatures overnight have re-frozen the pack but direct sunshine today should reverse this effect. At the mid-elevations watch for hard surface crusts to soften (this is where it rained on Tuesday). At the high elevations, watch for any new snow from Tuesday to become wet and possibly release into shallow wet sluffs.

Additional Concern
  • 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

In high areas of the Alpine where 2-6″ of new snow fell on Tuesday, watch for lingering wind slabs that could still be touchy. These are likely to be quite shallow in the Turnagain Pass zone but thicker (10-14″) in the Girdwood Valley where up to 10″ of snow fell. With an old crusty surface underneath, identifying drifts and how the winds blew the new snow around should be fairly easy.

*Watch for the sun to heat up and re-activate wind slabs later today in the Girdwood/Portage Valley and other areas that received snow from Tuesday.

**CORNICES:  Watch for cornice falls in the Alpine. There are been a few that have released in the past week and sunshine today will add to their instability.

Thu, April 21st, 2016

Two days ago, on Tuesday, a weak system moved through and added .2-.5″ of rain up to elevations between 1,500′ and 2,000′. For snowfall, there was 2-4″ of heavy snow that fell above 2,000′ in the Turnagain Pass area with up to 10″ in favored areas of Girdwood Valley and Portage Valley (believe it or not). The snow and rain was accompanied by strong Easterly winds averaging in 25-30mph range. This springtime storm moved out yesterday and during the past 24-hours we have seen no precipitation and light Easterly ridgetop winds. Temperatures were warm yesterday (40’s at 1,000′).  

Overnight, skies have cleared and temperatures have cooled dramatically. Valley bottoms are in the 20’sF and an inversion in place with ridgetop temperatures near 30F. For today, mostly clear skies are on tap with possible valley fog. Ridgetop winds are slated to be light from the East, 5-10mph. The sun should warm things up dramatically by the late afternoon.

For Friday we are expecting winds to increase from the East, cloud cover to move back in and a chance for precipitation as a low-pressure spinning in the gulf pushes a frontal band our way. Moderate Easterly ridgetop winds and showery conditions look to persist into Saturday and Sunday. Significant snowfall is not expected and the rain/snow line should be close to 2,000′ once again.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36   0  0 108  
Summit Lake (1400′) 39   0    0 23  
Alyeska Mid (1700′) 37   0    0 92  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 27   NE   9   24  
Seattle Ridge (2400′) 30   SE   10   27  
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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.