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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, January 22nd 2019 7:00 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

A generally LOW avalanche danger exists across all elevations bands for the Turnagain area today. Triggering a slab avalanche is unlikely but not impossible. As winds increase and snow falls the danger may rise to MODERATE in the Alpine late in the day. Pay attention to changing conditions and expect the avalanche danger to increase overnight. Avoid/limit your exposure time under glide cracks, give cornices a wide berth and watch your sluff.

SUMMIT LAKE / JOHNSON PASS:  A poor snowpack structure exists in this area, which is very different than Turnagain Pass. Triggering a slab avalanche is trending toward unlikely, yet may not be out of the question. Evaluate the snowpack and terrain. 

 


 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The bulk of the approaching storm is not forecast to impact the area until late tonight into tomorrow. Yesterday we received a trace of snow which fell on top of surface hoar and near surface facets that formed over the past weak. This barely buried weak surface snow could become a concern as snow accumulates, especially in terrain that has a melt-freeze crust or wind hardened snow below the weak snow. Today it will be important pay attention to the weather and changing conditions. Shallow storm slabs may quickly form in the Alpine as snow falls and the wind increases.  Watch for blowing snow, cracking below your skis or machine and use small test slopes to assess whether the new snow is bonding to the old snow. 

Finding an old isolated slab especially in upper elevation terrain in Girdwood, Portage or Placer is not completely out of the question. This part of the advisory area received more snow in the last storm. There has been one known human triggered avalanche that failed in the facets below the new snow, which was last Thursday in the Placer ValleyLow danger before the storm does not mean no danger. Practice good travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones are key ways to minimize risk. Ease into steep terrain and factor in the consequences should you encounter one of the following:

  • An outlier slab avalanche: 
    • Triggering a slab avalanche would most likely occur on an exposed 'unsupported slope' that sits above a cliff or steep rocky terrain. An old wind slab or a pocket of buried near surface facets and/or surface hoar 5"-2' below the surface may be lurking in an isolated area.
  • Glide avalanche:  
    • Identify glide cracks and avoid spending any time under these features. Glide avalanches are completely unpredictable and not human triggered.
  • Cornice fall: 
    • Remember cornices often break farther back from ridges than expected. Give them a wide berth.
  • Loose Snow avalanche (sluff):
    • Be aware of fast moving surface snow in steep terrain. 


Treeline surface hoar on Tincan, 1-20-19. Photo: Troy Tempel


Additional Concern

Persistent Slabs

South of Turnagain - Johnson Pass/Summit Lake zone: poor snowpack structure exists in these areas.  Multiple mid-pack weak layers of facets and buried surface hoar have been found as well as a facet/crust combination in the bottom of the snowpack. No recent avalanche activity and calm weather has allowed the pack to slowly adjust. However, it still important to evaluate the terrain and snowpack. Upper elevation terrain with hard, wind-affected snow over the buried weak layers is the most suspect. 


Mountain Weather

Yesterday: Skies were mostly cloudy skies with very light showers during the day. Easterly winds were 5-15 mph with gusts into the 20s. Temperatures were in the 20Fs to high teens. Overnight temperatures increased slightly. 

Today: Mostly cloudy skies and snow showers likely in the afternoon. Easterly winds will increase gusting into 30s during the day and 40s overnight. Temperatures will be in the 20Fs and low 30Fs. Rain/snow line forecast to be around 800'. Precipitation will increase overnight. 

Tomorrow: Snow with rain at lower elevations likely. Easterly winds increasing throughout day with gusts into the 70s and temperatures in the 20Fs and 30Fs. As this series of fronts impact the region expect temperatures to rise and periods of heavy precipitation especially near the coast through Thursday. Another storm system is on track for Friday. 

*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed. We are currently working to replace it.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  trace   0 50 
Summit Lake (1400')  23   trace    0  21 
Alyeska Mid (1700') 27  trace   0.07 35 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19  NE   7 24 
Seattle Ridge(2400')  24   *N/A  *N/A  *N/A 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
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