CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Tuesday, December 29th 2015
Created: Dec 29th 6:29 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

FCNFAIC is now accepting applications for TWO NEW scholarships! Both scholarships are for avalanche education up to $500. One will be awarded to a snowmachiner and the other to a skier or non-motorized user.

 Please include in your application: name, mailing address, your financial need and how you plan to spread avalanche awareness to your community post-award.  Applications due by 10PM on January 6th.  Please send your applications to chugachavyfriends@gmail.com

The Friends-CNFAIC board looks forward to hearing from you!


The Bottom Line

CONSIDERABLE avalanche danger exists in the backcountry today above 1,000’.  Strong winds and new snow have added substantial weight to a tenuous snowpack with known weak layers where potential exists to trigger a wind slab 3+ feet deep on leeward slopes (West and South).  Cornices are also growing quite large and are a legitimate concern whether you find yourself above or below one of these behemoths.  Cautious route finding and conservative decision-making will be essential today as you move through the backcountry.

Below treeline the danger is MODERATE specifically in channeled terrain where an avalanche releasing high above you can run into the low elevations.


Primary Concern

A 112mph gust on Sunburst yesterday and a flipped over tractor trailer on the Portage Valley Highway are both indicative of a wind slab issue today.  Winds were primarily out of the ENE yesterday and overnight meaning slopes with a south and westerly tilt will be most suspect for triggering a wind slab.  Strong winds such as this have a tendency to build wind slabs mid slope (further from the ridge crest).  For skiers this means that mid-run you may find yourself on the slab; and for snowmachiners who generally attack a slope from the base, recognize that wind slab may be mid-hill climb, well below the ridge crest. 

Watch out for any obvious red flags today such as whumphing, shooting crack or recent avalanches.  Whumphing was present for several groups yesterday and is indicitive of a weak layer collapse.  Sometimes this is harder to identify from your snowmachine but it’ll be worth the time today to slow down and keep a keen eye/ ear.  As wind has a tendency to distribute snow unevenly across any given slope, a skier or snowmachiner is more likely to influence the weak layer in these areas where the slab is thinner.  Shallow spots near rock outcrops or alder will be the more likely trigger points where your skis or snowmachine track is physiclly that much closer to the weak layer.  

Folks were generally keeping terrain choices mellow yesterday, including these two kite skiers capitalizing on the sustained winds yesterday afternoon in the shadow of Sunburst.  


Secondary Concern

These warm, windy storms have a tendency to grow cornices rapidly here in the Chugach and Kenai mountains.  These 'backcountry bombs' deserve an extra wide berth today and throughout this “New Year storm cycle”.  A cornice breaking either naturally or from human traffic has the potential to trigger a large avalanche as it falls on the slope below.  Limit time spent below a cornice and if travelling along a ridge, stay back waaaaaay further than you think necessary to give yourself that added margin of safety.


Additional Concern

Given the current structure of our snowpack, we have reason for concern as these potent late-December storms are falling on top of a couple of older known persistent weak layers.  With more weight in the form of snow and wind yesterday and today, these weak layers can edge closer to their point of failure, laying in wait for a trigger.  Yesterday, Alaska Railroad avalanche reduction crews had several avalanche results using explosives to trigger these weak layers.  They saw debris running to the valley floor in channelized terrain.


Mountain Weather

Heavy snow and strong northeasterly winds on Turnagain pass subsided around 3pm yesterday after a 112mph gust on Sunburst and 4-6” of heavy, wet snow fell at 1,000’.  Skies broke apart allowing a brief glimpse into upper elevation start zones.  Temperatures hovered right around 32F at 1,000’ and 35F at sea level.  Rain and strong winds persisted throughout the day in the Girdwood and Portage valleys. 

Today we can expect temperatures in the mid-30’s and ridgetop winds from the SE in the 20-40mph range.  Cloud cover will be on the increase throughout the day and precipitation in the form of a rain/ snow mix at 1,000’ will be light during daylight hours and increasing tonight.

Late tonight and into tomorrow we’ll be feeling the full effect of another powerful and unseasonably warm and windy Gulf of Alaska storm.  The NWS has issued another high wind warning that goes into effect tomorrow morning.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  31  4 .7  67 
Summit Lake (1400')  34  1  .3 20 
Alyeska Mid (1700')  31  4 .6  60 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  24  E 28  112 
Seattle Ridge(2400')  26 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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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.
FCNFAIC