CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, March 16th 2014
Created: Mar 16th 6:24 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
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
BP Alaska
Special Announcement

Placer river and Skookum are CLOSED to motorized use from the rain last week.  Seward district riding areas are OPEN.  Check the bottom of this page for the latest information on riding areas.


The Bottom Line

A CONSIDERABLE avalanche danger exists on all aspects and elevations 2,000' and above. Slab avalanches 3-5' deep remain possible for a person, group of people or snowmachine to trigger on slopes 35 degrees and steeper. These have the potential to be triggered remotely from ridgelines or the bottom of slopes. Additionally, watch for fresh wind slabs up to a foot deep on West, South and Northerly aspects as the Easterly winds pick up through the course of the day.

At elevations below 2,000' there is a MODERATE danger where 2-5" of loose snow sits on a snowpack composed of moist snow and crusts.

**These are dangerous avalanche conditions and sticking with conservative travel in avalanche terrain is recommended. 

Safer areas to recreate are in the flats and on slopes less than 35 degrees in steepness - or below 2,000' and away from runout zones.


Primary Concern

Yesterday was a classic sunny Saturday after a storm cycle and many folks were out enjoying Winter Part III. Along with this were reports of a handful of large human triggered avalanches. Luckily, no one was reported caught as they were 3-5'+ deep, large and dangerous. Details are limited, but here is what we know:

-  Widow Maker Face (West facing, 2,500' - Seattle Creek drainage). This avalanche was 5-6' deep and likely remotely triggered from the ridgetop by a group of riders. More details HERE.

-  Four deep pockets in Tincan's Hippy Bowl (Southwest facing, 3,500/3,000). These slides are suspected to have been remotely triggered from an adjacent sub-ridge. More details HERE.

-  Palmer Creek (South of Hope). At least one large snowmachine triggered avalanche was reported in this drainage - very little information at this time.

Photo below: Widow Maker avalanche - photo was taken by a person looking North on Seattle Ridge.

 

The avalanche activity noted above is suspected to be failing at the old snow/new snow interface. The new snow consists of the combined 3/10-3/14 storm snow that has settled into a very strong slab around 30" to 4' thick (thicker in wind loaded areas). The weak layer is suspected to be a thin 1-2cm layer of old weak snow and buried surface hoar sitting above the late February crust.

Lowering likelihood - high consequences:
The slab is thick enough that triggering the weak layer is difficult and the weak layer is showing signs of adjusting to the new load. However, this set up deserves our respect regardless. The sole reason is the sheer size and destructive power of a potential slide. 
If you haven't noticed from the reports of yesterday's activity, these are deep and dangerous avalanches - the kind that if you are caught up in, are likely not getting out of. Conservative terrain management is key once again for a safe day in the backcountry.


Secondary Concern

Ridgetop winds are forecast to pick up to ~20mph from the East by noon today and continue to increase into the 40-50mph range by tonight. Although only around an inch of new snow is expected this afternoon, there is upwards of 4-10" of loose snow already on the surface available for the wind to transport. With these factors in mind, watch for winds to form slabs near ridgelines, on rollovers or by cross-loading in gullies. These slabs will likely be in the foot deep category and sensitive to human triggers.

Additionally, any wind loading and/or wind slabs triggered could stress buried weak layers and aid in triggering a deep slab.


Mountain Weather

Yesterday was our first clear sky day since last Sunday; between Monday and Friday two storms rolled through bringing 4-5' of dense snow to the Eastern Turnagain Arm mountains. During the past 24-hours temperatures have averaged in the teens from 1,000' to 4,000' and ridgetop winds have been light, 5-10mph, out of the East. Overnight, temperatures have dropped to the single digits above 1,000' and clouds have begun to stream in.

Today, cloud cover and light snow showers will increase through the day due to a front sliding through from the West. Around an inch of snow is expected by this afternoon with another 3-5" of low density snow possible overnight. Temperatures will remain plenty cold for snow to sea level - teens at 1,000'. Winds from the East are slated to pick up this afternoon and by midnight blow in the 50mph range.

Tuesday, light snowfall is expected to continue with up to another 2-4" accumulating. Winds look to remain strong from the East and temperatures cold enough for snow to sea level.

 

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.
FCNFAIC