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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, February 7th 2017
Created: Feb 7th 5:09 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
Special Announcement

Many areas around Southcentral, Alaska including the Southern Kenai Mountains, Seward, Snug Harbor and Lost LakeAnchorage Front RangeHatcher Pass continue to have an unstable snowpack. Human triggered large avalanches, breaking near the ground, are possible. Please see link above for recent activity. Keep in mind avalanches can be triggered remotely, from below or mid-slopeCareful snowpack evaluation and cautious route-finding is essential. 

Mark your calendars: This Saturday CNFAIC and the Anchorage Snowmobile Club will be hosting a FREE Avalanche Rescue Workshop at Turnagain Pass, 11am -12:30pm in the Motorized parking lot. We will focus on practicing with your avalanche beacon, probe and shovel. This workshop is open to everyone and anyone, novices and experts, that recreate in avalanche terrain – snowmachiners, skiers, snowboarders, etc… Click HERE for more details. 

              


The Bottom Line

There is a generally LOW avalanche danger in the Turnagain Pass region where triggering an avalanche in unlikely. However, there are areas above 1,500' that have a poor snowpack structure and there remains the chance for triggering a large slab avalanche (2-5' thick) that breaks near the ground; this situation is keeping the danger MODERATE. Likely trigger points are thin areas on a slope (i.e. where rocks are showing through) and likely triggers are large, such as groups of people, snowmachine(s), and cornice falls. Additionally, there are some normal caution problems to keep an eye out for today, these are: shallow fresh wind slabs, sluffs in steep terrain and cornice breaks. 

Summit Lake and Girdwood:  A poor snowpack structure exists in these areas as well and human triggered avalanches breaking near the ground are possible. Make sure and check the Saturday Summit Summary HERE.

*This is a low probability but high consequence situation and it is critical that safe travel protocols are executed and avalanche rescue gear is carried. This means only one person on a slope at a time - in the event an avalanche is triggered, there is/are people capable of rescue. Also, have escape routes planned and watch your partners. These practices likely saved the life of a person fully buried near the Seattle Ridge Headwall on Friday, Feb 3rd (this near miss report will be published by tomorrow morning).


Primary Concern

The brilliant sunny skies and quiet weather conditions we have been having for a week now continue to allow folks the opportunity to put tracks on the mountainsides all over the Chugach National Forest. This is what February is about! Despite the high number of people testing the slopes with snowmachines, skis and snowboards, we have only had two large and dangerous avalanches triggered, but this is enough to keep our guard up - these were both on Friday HERE and HERE. The likelihood for someone to find and triggered a large slab is decreasing each day as the snowpack adjusts slowly, but it's the consequences that are scary and why we all need to be on guard and utilize safe travel protocol. 

Deep slab avalanches?  Photo below is the crown from one of the avalanches triggered on Friday, this one by a snowmachiner on the Seattle Ridge Headwall. We were able to visit the site yesterday and assess the avalanche. We found various degrees of weak faceted snow in the bottom foot of the snowpack that was the culprit weak layer. This slope is also near the ridge at 3,700' and is highly affected by wind with thick areas of the slab up to 4' (seen below) and thin areas less than 2'. We dug a pit in a thin spot and had no results in stability tests, pointing to stable conditions despite the weak snow at the bottom of the pack. My point being, one is likely to have no signs of instability and there could be many tracks on a slope (as was the case in the below avalanche) before an avalanche occurs. 

This deep slab problem is tricky and the important thing is to know you may be on a slope with weak snow underneath a stiff slab 2-4+' thick that just needs a trigger in the right spot. Again, likely trigger spots are where the slab is thin, possibly next to rocks. Likely triggers are large: snowmachines, groups of people or cornice falls. 

 


Additional Concern

Cornices continue to bend over with the warm conditions and a piece of one in Warm up Bowl (1st Bowl) on Seattle Ridge broke off in the last day or two (photo below). These 'backcountry bombs' are worth avoiding and giving a wide berth. If your route takes you underneath them, travel quickly and minimize your exposure time.

 

Wind slabs
Winds have been gusty in some areas, mostly from the South and East. These may have formed shallow winds slabs on leeward slopes and something to watch for today.

Loose snow sluffs
Sluffs on steep slopes harboring soft settled snow are possible again today. These have been relatively low volume but still something to watch for in the very steep terrain.


Over the weekend the sun was in full force, as anyone who was out can attest to. Sun crust, up to an inch or more thick, is now on many Southerly aspects. Photo on left is from the Alaska Avalanche School Level 1 course showing the extent of the sun crust at treeline on Tincan. Photo on right is from the Seattle Ridge up-track, this Southeast facing slope harbors frozen roller balls and a shimmering sun crust. Soft settled powder 4-8" deep can be still be found in many shaded areas however.

 


Mountain Weather

Clear skies were seen again yesterday with a moderate inversion in place. Temperatures in the valley bottoms were 5-15F while ridgetops were in the 25-30F range. Ridgetop winds were light from the South and East with gusts into the upper 20'smph at the Seattle Ridge weather station that is close to Turnagain Arm.

Another bluebird day is on tap today with light Southeast ridgetop winds (5-15mph). Temperatures have decreased overnight and should bump back to the mid 20's F on the ridgetops today. Valley bottoms will remain cool, in the 5-15F range.

There looks to be a chance for a cold low-pressure system to bring snowfall our way Wednesday night to Friday. Stay tuned as to how this develops tomorrow morning!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24 52 
Summit Lake (1400') 15  23 
Alyeska Mid (1700') 27  47 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  19 
Seattle Ridge(2400') 25  SE  11  26 

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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