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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, April 23rd, 2016 - 7:00AM
Expires
Sun, April 24th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger remains  CONSIDERABLE  below 2500′ due to glide avalanches that are releasing daily in popular recreation areas.  Avoid being under the runout of glide cracks.  In addition, human triggered and natural wet loose avalanches are possible in steep terrain due to saturated snow, purple rain and warm temperatures.  

In the Alpine the avalanche danger is generally LOW,  keep in mind  pockets of lingering wind slab on lee slopes and wet loose avalanche potential in steep terrain. As always steer clear of cornices.

*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.

Special Announcements
  • The Forest Service has CLOSED Turnagain Pass to motorized use due to lack of snow cover. Whittier is also now CLOSED. Remaining areas that are OPEN to motorized use are Snug Harbor and Summit Lake, both on the Seward District.  After no motorized openings on the Forest last season, Turnagain Pass was open this winter from December 13th until April 22nd – that is 132 days!

  • 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!!  
Sat, April 23rd, 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. 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

As mentioned in the advisories earlier this week, the glides have “migrated” across the road. Magnum and Cornbiscuit both had glide avalanches occur in West facing terrain in the last few days. New cracks continue to appear and existing cracks keep growing. With new glide avalanches being observed daily the travel advice remains the same… Avoid being under the runout of glide cracks. The small glide crack near the common skin track on Sunburst has grown and is above a terrain trap. 

 

 

Magnum and Cornbiscuit

.

Sunburst glide crack

 

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

The rain/snow line today is forecasted to be 4100′. The precipitation amounts should be minimal but the overall wetting of the snowpack will rise in elevation with the warm temperatures. There was little to no freeze last night. 2-5″ of snow fell on Tuesday above 2000′ (more in the Girdwood Valley). Below 1800′ the snowpack is saturated and barely supportable.  All these ingredients combine for wet loose avalanche potential today. Below 2500′ triggering a wet loose avalanche is likely in very steep terrain. In the Alpine wet loose avalanches in the new snow may also be a consideration as the newer snow gets more and more saturated. Pay attention to how much snow is getting pushed while making a turn and watch for moving snow that may entrain surface snow as it gets moving. 

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

At elevations above approximately 2,500′ (in the Alpine) the snowpack is generally stable. Watch for unstable snow on isolated terrain features.

– Lingering wind slabs

– Wet loose avalanches

– Cornice falls 

 

Weather
Sat, April 23rd, 2016

Yesterday was overcast and there were rain showers throughout the day. Temperatures were in the low 40Fs at 1000′ and the low-mid 30Fs at 3000′. Winds were moderate and easterly.  

Today will be mostly cloudy with rain showers forecasted throughout the day. Temperatures are expected to climb into the 40Fs at 3000′. Easterly winds will be 10-25 mph.

Temperatures may cool a bit overnight but Sunday looks to be very similar to today. The overall pattern of cloudy skies and rain showers remains in place for the week to come.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 39   0   0   106  
Summit Lake (1400′)  41 0 0 20  
Alyeska Mid (1700′) 37   0 .15   90  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  31  ENE 20    41
Seattle Ridge (2400′)  33 SE    15  33
Observations
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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.