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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, April 28th, 2015 - 7:00AM
Expires
Wed, April 29th, 2015 - 7:00AM
Forecaster
John Fitzgerald
Avalanche risk The Bottom Line

The avalanche danger is MODERATE in the Alpine where wet loose, glide avalanches and unstable cornices are the main problems to contend with today.

The danger is LOW at Treeline, where avalanches are unlikely with the exception being shallow wet loose activity.

Special Announcements

Avalanche Center operations are wrapping up this week. This is the final advisory of the 2014-2015 season.   We will post our end of the season/springtime tips report on Thursday, April 30th. A BIG thank you to all of you for tuning in this winter despite the challenging snow year!!

Tue, April 28th, 2015
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
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
  • 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

Sustained mild temperatures have helped to destabilize the snowpack over the past several days.  Overnight refreezing has occurred, but is likely only superficial.  As a result there are several ways in which snow can release today in the Alpine:

Wet Loose
Both natural and human triggered wet loose avalanches are likely on slopes over 40º in steepness.  Volume of these will be generally low but will increase on sustained steep slopes.

Glide Avalanches
While this is not a widespread problem, we observed several glide releases yesterday on the South side of Tincan ridge (see photo below).  A shed cycle of sorts has begun in certain areas such as this.  Exposure to the sun will increase the chances of full depth wet slabs releasing today.

Glide/Shed Tincan

Cornices
Yesterday my partner and I unintentionally triggered a very large section of cornice on Sunburst ridge (see photo below).  More details HERE.  This is a great example of why it is critical to give these behemoths an extra wide berth.  If you are unsure of where the terrain ends and the cornice begins, move to where you are certain that there is ground beneath you.

Cabin sized cornice chunk

Warming will be gradual today as we will be under cloudy skies for the majority of the day.  Despite this, there is still a lot of heat contained within the snowpack.  Keeping slope angles on the low end on all aspects and avoiding cornices will be important ingredients for managing these avalanche concerns in the mountains today.

Additional Concern
  • Announcement
    Announcement
Weather
Tue, April 28th, 2015

Over the past 24 hours the mountains around Eastern Turnagain Arm have experienced mild temps, cloudy to sunny skies and occasional rain showers.

Today light Northerly flow will keep skies cloudy and bring a chance of light rain/snow.   The sun will make an occasional appearance throughout the day.   Rain snow line will be around the 2,500′ level.   Winds will be Northwest at 10-15 mph.   Temperatures at 1,000′ will climb into the mid 40s F.

The extended outlook is calling for a continuation of unsettled weather bringing mild temps, cloudy skies and showery activity.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 40 0 0 67
Summit Lake (1400′) 39 0 0 11
Alyeska Mid (1700′) 37 0 0 41

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28 var 7 22
Seattle Ridge (2400′) 29 var 13 29
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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.