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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, April 6th, 2016 - 7:00AM
Expires
Thu, April 7th, 2016 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

The potential for mid-elevation glide avalanches is keeping the avalanche danger at  CONSIDERABLE today. These are most pronounced at 3,000′ and below. Many popular slopes are harboring dark brown glide cracks that have potential to release day or night.   Cautious route finding and careful terrain evaluation is essential to  avoid being under the run out of glide cracks!

The avalanche danger is LOW in the alpine where a stout and supportable surface crust sits under 2-4 € of wet snow from yesterday.  

*As glide avalanches continue to release, summer use trails with avalanche terrain above should be avoided. The Byron Glacier trail in Portage Valley is not recommended and the Turnagain Arm Trail between Bird and Girdwood, remains CLOSED.

Special Announcements

FREE rescue clinics and general avalanche information for those headed to Arctic Man this week.  Click  HERE  for more information.  The snowpack has been reported to be very unstable in the Hoodoos with many human triggered avalanches over the weekend. Please be on your guard and don’t forget your beacon, shovel and probe.

 

Wed, April 6th, 2016
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
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. 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
  • 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

Glide avalanches continue to steal the limelight and for good reason as it only takes a short drive through Turnagain Pass to witness first-hand the quantity of glide avalanches and sheer destruction that these can bring.  It is important to stay well away from existing cracks and limit your exposure time to glide avalanche run out zones.  We’ve been saying it for a while but to get caught up in a glide avalanche will undoubtedly prove fatal.

A very large glide crack has been slowly opening and creeping toward the common snowmachine up-track on Seattle ridge.  If venturing toward the back bowls today, travel fast in order to limit your time spent exposed to this growing glide crack.

Avalanche Problem 2
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

Wet loose avalanches:  2-4” inches of wet snow yesterday fell on a supportable crust above about 2,000’.  We can expect up to another 2-4” today.  Stubborn, shallow wet-loose avalanches may be possible in very steep alpine terrain but these shouldn’t prove much of an issue for skiers or snowmachiners today. 

Keep in mind that LOW danger does not mean NO danger.  Aside from glide avalanches, we haven’t seen much wet slab activity yet but it is getting to be that time of year where wet slabs become a concern with shallow overnight freezes and warm daytime temperatures.  

Cornices:  We are still waiting for the Alpine to warm up enough to start seeing a natural cornice fall cycle.  We do know that cornices are close enough to failure that skiers or snowmachiners can influence a failure by travelling on a corniced ridge and the potential for a human-trigger is a very real concern.  Remember these have a tendency to break much further back than one might expect.

Wind slabs:  Winds picked up enough overnight that high in the alpine (where dry snow exists) shallow wind slabs likely exist in leeward terrain.  These are not likely to be deep or large, but could prove tricky in extreme terrain.

Weather
Wed, April 6th, 2016

Yesterday was mostly cloudy with light winds from the east.   Temperatures averaged 29 degrees during the day on Sunburst (3,880′) with 2-4 € of new snow falling above about 2,000′ and light rain below.   Overnight, it looks like there was another shallow freeze between 2,000′ – 4,000′.

The forecast today calls for partly to mostly cloudy skies again with rain/ snow showers throughout the day.   We may see 2-4 € of new snow above about 2,000′ and light rain below.   Temperatures will be in the low 40’s at 1,000′ and low 30’s to high 20’s around ridgetop locations.   Winds will be primarily from the East in the 15 €“ 35mph range.  

Tomorrow and into Friday may bring us a brief break from this showery regime before returning to unsettled weather over the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 37   0   .1   117  
Summit Lake (1400′) 38    0 0   36  
Alyeska Mid (1700′) 35    trace/ rain .14   103  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   E 11   38  
Seattle Ridge (2400′)  29  SE 15   28  
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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.