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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Saturday, April 29th 2017
Created: Apr 29th 5:32 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
The Libby Group
Special Announcement
  • Today, Saturday, is the LAST avalanche advisory that will be issued for the 2016/2017 season. We will issue a general Springtime Avalanche Tips on Monday, May 1st. Also, look for our Annual Report to come out in the next two weeks. Thank you for tuning in this season!

  • Observations: We will continue to post observations all spring and summer - so please keep us, and the community, posted on any snow/avalanche information you may come across on your upcoming adventures! A big THANK YOU to everyone that has submitted information to the center!!

  • Motorized area open/closure update:  Turnagain Pass will remain open through May 14th. All other areas will close May 1st (this includes Johnson Pass, Whittier, Lost Lake). See details at the bottom of this page.

The Bottom Line

The avalanche danger is expected to remain at MODERATE on slopes above 1,000' for wet avalanches this weekend. The danger could rise to CONSIDERABLE by the early evening hours in the event of significant daytime warming. Keep in mind the snowpack continues to slowly warm and destabilize as it undergoes the springtime transition. Human triggered wet loose and wet slab avalanches are possible on slopes over 35 degrees with a wet snowpack. Natural wet snow avalanches will also become possible later in the day as the snowpack becomes wet. Additionally, glide cracks continue to slowly creep open and can release without warning. 

There is a LOW avalanche danger below 1,000’ where little snow remains. 

Hiking on summer trails during the springtime warm-up (including the Byron Glacier trail, Crow Pass, etc).  Extra caution is advised for trails that cross under avalanche paths. The danger will increase in the afternoons with possibility of an avalanche occurring above that could send debris to snow-free zones. 

SUNDAY APRIL 30th AVALANCHE OUTLOOK: The avalanche danger and issues will be the same for tomorrow, Sunday. For Monday however, heads up that a cooler storm system will be moving in and could increase the avalanche danger.


Primary Concern

Cooler weather and a chance for a few snow flurries above 2,000' should keep most of the springtime rapid warming at bay this weekend (and possibly into next week). That said, we are still seeing a handful of avalanches each day as the snowpack transitions from dry to wet. Most of these have been relatively small wet loose sluffs and glide releases. The most notable however, is a natural wet slab avalanche that occurred Thursday(ish) in the Girdwood Valley (photo/description below). This slide was on a Northerly aspect around treeline and illustrates how all aspects are suspect currently. During the past 2 days there has been some type of avalanche documented on North, West and South slopes (I'm betting there is an Easterly one out there as well).

The key for a safe day in the mountains is knowing what slopes are wet, saturated and unsupportable (unstable and dangerous) and what slopes are frozen (stable). This is not always as easy at it seems. Carefully monitor surface crusts throughout the day and be aware of steep terrain above you that may be heating up faster than you may expect. Steep rocky terrain baking in the sun can begin to produce wet sluffs, which could in turn trigger a wet slab, and send debris to valley bottoms where the surface is still frozen. 

WET SLAB, WET LOOSE and CORNICE FALLS - things to keep in mind if you are headed out: 

  1. Are you seeing recent avalanches?
  2. Is the snowpack frozen or wet and soggy?
  3. Are you punching through a shallow crust into wet soggy snow? A shallow re-freeze is still weak and could avalanche.
  4. Are you in a runout zone? Can an avalanche releasing above wash debris over your location?
  5. Buried weak layers in the pack can make a small avalanche or sluff larger by propagating across the slope and/or stepping down.


Recent large slab avalanche on Orca Ridge/Big League, North aspect - released sometime close to Thursday, April 27th. This slide looks to have started as a wet loose avalanche then stepped down to the mid-pack and then again to the ground around 1500'.

 

Skier triggered wet loose sluffs on the Southwest shoulder of Sunburst from Thursday/Friday (old crown from early April storm cycle in background)

 

Farthest left natural wet loose avalanche on the West face of Magnum is also from Thursday/Friday (April 27/28), many older dark and melted out loose snow avalanches from earlier in the week on the right of the face 

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Secondary Concern

Glide cracks are also opening up and releasing on many slopes in the region with the springtime melt-down. At times it can be difficult to tell the difference between glides and wet slab avalanches. But that is beside the point - both are dangerous. The way to manage glide avalanches is to stay out from under any slopes harboring glide cracks! Check out the photo below from the motorized up-track. This slope is notorious for producing glide avalanches. Additional glide avalanche activity is expected today and through the week.

 

Note the opening glide cracks lower on Eddies West facing slopes?

 

Recent large glide avalanche on the lower Southwest facing Tincan terrain - in this area several glide cracks have released while several cracks and hanging in the balance.

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Additional Concern

There are several buried persistent weak layers in the snowpack; ranging from buried surface hoar 2-6' deep, mid-pack facets and facets near the ground. Shallow snowpack zones such as the Summit Lake area harbor depth hoar near the ground. On upper elevation North, West and Easterly aspects these weak layers could re-activate when the snowpack melts, becomes saturated and loses strength. If significant warming/melting occurs this weekend or into the workweek, keep in mind large slab avalanches are possible - both triggered by a person as well as naturally.


Mountain Weather

Partly cloudy skies with patches of sun filled the region yesterday before clouds moved in overnight with light precipitation; rain showers up to 1,500' and some wet flurries above this. Up to .1" of measureable precipitation fell in certain areas. Ridgetop winds have been moderate from the East, 10-20mph averages and stronger gusts. Temperatures have been cooler with ridgetops in the upper 20'sF and parking lot temperatures around 1,000' in the low 40'sF during the day.

For today and Sunday: As we remain in between large scale weather patterns we can expect partly cloudy skies with intermittent showers. This should give the area a chance for rain up to 1,500'-2,000' and snow above - intermixed with patches of sunshine. Ridgetop winds are expected to be light in the 5-10 mph range from the East. Temperatures will continue to be cool with ridgelines in the 20'sF and at 1,000' in the low 40'sF.

Monday and early next week:  A cool low-pressure storm system will move in bringing rain to 1,000'-2,000' and wet snow above this. Easterly ridgetop winds will increase into the 20's and 30's mph. Keep tabs on the recent weather on our weather page along with the NWS forecast discussion!

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 39  trace  0.1  51 
Summit Lake (1400') 38  11 
Alyeska Mid (1700') 37  trace 0.01  47 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 28  NE  25 
Seattle Ridge(2400') No Data  SE  17  30 

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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