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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, March 31st, 2016 - 7:00AM
Expires
Fri, April 1st, 2016 - 7:00AM
Forecaster
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is  CONSIDERABLE  today due to above freezing overnight temperatures, and increased warming from the sun today. Glide avalanches and natural wet loose avalanches in steep terrain are possible today. Human triggered wet loose avalanches are likely. Cautious route-finding and terrain evaluation are essential today. Avoid being under the runout of glide cracks.

Summer use trails with avalanche terrain above should be avoided due to the threat of natural avalanche activity from above. Byron trail in Portage Valley is not recommended and the Turnagain Arm Trail between Bird and Girdwood remains CLOSED for the winter.

*If you are headed to the Summit Lake area don’t forget to check  Summit Lake Summary.  

Special Announcements

ATTENTION PROCRASTINATORS!!!!  Today is the deadline to file for your 2016 Permanent Fund Dividend —  Remember The Friends of the CNFAIC is part of  PICK.CLICK.GIVE. Your donations are greatly appreciated and integral to making the CNFAIC possible and sustainable.    Be part of the ‘Movement’! Thank you for your support!

Headed to Arctic Man 2016? Don’t forget your beacon, shovel and probe! CNFAIC will be there all week and offering two FREE companion rescue workshops. Click  HERE  for more information. We hope to see you there!

Thu, March 31st, 2016
Alpine
Above 2,500'
3 - Considerable
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
  • 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

Will daytime temperatures reach a season high today? 

Sunny skies combined with unseasonable warm weather could push temperatures into the high 40F’s to mid 50F’s today.  Last night was the second night in a row of above freezing temperatures in the mid elevation zone and rain/snow line yesterday was observed around 2500’. At treeline 4-6” of wet snow is sitting on a supportable crust where wet loose avalanches will be a concern today on slopes steeper than 35 degrees. The size will be directly proportional to the size of the terrain, and larger slopes will be more dangerous where more snow is available to entrain and pick up momentum. In the alpine where drier snow is sitting on a smooth bed surface there is more potential for moist/wet slab activity. Pay attention for rollerballs and avoid being on or under steep slopes today.  The danger will increase with warming temperatures and solar impact throughout the day.

In Girdwood and Portage Valley where more snow has fallen over the last three days, expect wet loose activity to be larger. Cautious routefinding and a conservative mindset will be the best strategy for travel in the backcountry. 

 

 

Avalanche Problem 2
  • 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

The glide avalanche cycle continues without interruption. Yesterday another handful of new glide releases were identified between Girdwood and Turnagain Pass including a large glide avalanche that stopped just short of the Turnagain Arm bike path on Penguin Ridge.

In Turnagain Pass a glide crack on Seattle Ridge has been growing and is starting to threaten portions of the common uptrack.  A recent glide avalanche in this location, above this glide crack occurred on 3/29 in conjuntion with a storm slab. The debris pile is quite large and runs over well-traveled terrain. This should definitely warrant concern, today’s warm temperatures will only be weakening the snowpack. Glide avalanches are completely unpredictable and could happen at any moment, avoidance is strongly recommended.

Portions of the Seattle Ridge uptrack (in orange) are in the runout of a growing glide crack on Seattle Ridge. 

 

View of recent glide activity on East face of Seattle Ridge with a large glide crack in the foreground on Tincan SW aspect.

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

Cornices remain extremely large and perched along many ridgelines. These features deserve extra space and can break farther back than expected. Triggering a cornice will become more likely later in the day with sun and warming temperatures. 

Wind slabs: In the upper alpine (above 3500’) where temperatures have remained below freezing, wind slabs remain a concern on unsupported slopes and will be more suspect during the heat of the day with warming temperatures. These wind slabs could be extra touchy where they are sitting on a stout melt freeze crust below.

Weather
Thu, March 31st, 2016

Yesterday skies were mostly cloudy and with light scattered showers throughout the region. Ridgetop winds were averaged in the 20’s mph from the East. Temperatures ranged in the 30F to mid 40F’s, and remained above freezing overnight in the mid elevation zone.  Temperatures in the alpine were just below freezing yesterday and overnight.

Today skies will be mostly sunny with patches of fog. Daytime ambient air temperatures may reach the 50F’s at sea level and 40F’s in the alpine. Winds are expected to be light to moderate from the East and no new precipitation is expected today.

Tomorrow a front will move through Southcentral Alaska bringing another round of rain showers. Temperatures are expected to remain above freezing in the mid elevations and rain/snow line is expected to be around 3000′.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 39   rain   0.2   123  
Summit Lake (1400′) 39   rain   0.1   39  
Alyeska Mid (1700′) 36   rain   0.13   108  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   ENE   17   54  
Seattle Ridge (2400′) 31   SE   31    59
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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.