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Fri, March 31st, 2017 - 7:00AM
Sat, April 1st, 2017 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

Snowfall, rain and strong winds are creating a  HIGH  avalanche danger at all elevations in Turnagain Pass,  Portage, Placer and Girdwood Valley where natural avalanches 2-3′ thick are likely today.  Travel is not recommended in avalanche terrain where natural avalanches are likely occurring due to rapid loading. Steer clear of gullies and the bottom of large and steep slopes in the event an avalanche occurs above you.

Hiking in Portage Valley:  Travel along, and past, the designated Byron Glacier trail is not recommended due to exposure to avalanche terrain. Natural avalanches are possible today that could send debris to valley floors.

Summit Lake:  The storm cycle brought 6-10″ of new snow and gusty winds. Read the  Saturday Summit Summary  HERE  and an observation from yesterday HERE.  

Special Announcements

There will be intermittent traffic delays today, Friday, March 31, 2017 on the Seward Highway for avalanche hazard reduction work between Bird and Portage near mileposts 100 to 80. Motorists should expect delays of up to 1 hour between 8:30 am and 1:00 PM.

Today is the deadline for applying for your 2017 PFD!! Please consider showing your support for public avalanche centers when applying – the Friends of the Chugach National Forest Avalanche Center is an  official  Pick. Click. Give. organization!

*A reminder that the Skookum Valley closes to motorized use on Saturday,  April 1st.  All other motorized areas remain open – see area status on the bottom of this page for more information.

Fri, March 31st, 2017
Above 2,500'
4 - High
Avalanche risk
4 - High
Avalanche risk
Below Treeline
Below 1,000'
4 - High
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
  • 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

New snow and wind have combined to create very unstable slabs, 2-3’ thick. 6-12″ of snow fell in the last 24 hrs adding to the previous storm totals. Ridgetop winds from the East (SE to NE) picked up yesterday into the 30s and 40s mph and continued with several gusts in the 70s overnight at Sunburst weather station. Sustained winds are forecasted to continue today. Fresh cornices could fall and wind slabs will be found in leeward terrain. Rain started falling at lower elevations and rain/snow line is expected to rise to 2000′ today. An additional 6” of snow is forecasted for the higher elevations today.  Slabs will likely release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be extra important to avoid being near any runout zones today. Human triggered avalanches are likely.  An observer yesterday reported very touchy conditions in the Tincan trees. Storm slabs in areas protected from the wind continue to be a concern. Remember that prior to the storm starting Tuesday, the snow surface was surface hoar and/or near surface facets or a sun crust, not layers that new snow bonds well with. This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” the avalanche hazard today. 

New snow in Summit Lake not bonding to the surface hoar buried below.  Remember the Turnagain Advisory area has 2-3′ of snow on this same set-up. Photo: Conrad Chapman

 Turnagain motorized lot yesterday, Poor visibility due to snowfall and sustained winds. Photo: Conrad Chapman

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

Rain falling on snow to 2,000’ will weaken the surface snow and possibly an older layer beneath. Temperatures are forecasted to rise to 40F at lower elevations today. Wet loose avalanches are likely and wet slab avalanches are possible due to a layer of buried surface hoar and/or near surface facets 2-3’ below the surface. In channeled terrain an avalanche from above will likely entrain weak snow in the lower elevations increasing overall volume. Triggering a wet avalanche in the lower elevations could have high consequences if pushed into or over terrain traps such as cliffs, gullies, or trees. Again it will be important to avoid steep terrain and maintain a conservative distance from all runout zones.  

Additional Concern
  • 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

Don’t forget that our snowpack harbors several old layers of weak snow. Avalanches releasing in the storm snow have the potential to ‘step down’ into these layers. Furthermore, as the new snow piles up and begins to stick to the old snow surface, avalanches breaking into them is possible as the load increases. Both of these situations can create a much larger avalanche – something to keep in mind as the storm cycle continues into the weekend. 


Fri, March 31st, 2017

Yesterday was stormy with SE-NE winds gusting into the 50s and snow falling throughout the day, a foot on Turnagain Pass and 6-8″ in Girdwood. Temperatures were in the 20Fs to low 30Fs.

Overnight winds increased with gusts into the 70s. Temperatures rose into the mid 30s and are slowly climbing this morning. Rain started falling at lower elevations. Today rain/snowline is forecasted to rise to 2000′ as warm air pushes into the region. Up to an additional 6″ of snow could fall today at higher elevations. Winds will continue from the SE-NE 20-30 mph with gusts into the 50s. Precipitation will continue tonight into tomorrow.  

The active weather pattern will continue into next week as a series of lows move into the Gulf.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30   9   .9   78  
Summit Lake (1400′) 30 2   .2 34  
Alyeska Mid (1700′) 29 8 .5   80

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  20 ENE   35    80
Seattle Ridge (2400′) 23   SE 30    51  
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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.