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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, February 16th 2014
Created: Feb 16th 6:35 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.
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

New snow over the past week is helping to rebuild the snowpack in areas that were showing bare ground after the January rain and warmth.  Motorized areas on the Chugach National Forest remain closed to avoid resource damage.  The good news is that we are getting closer to reopening these areas.  Check the bottom of the page for the latest updates as well as the Chugach National Forest website.


The Bottom Line

The avalanche danger is MODERATE at all elevations and aspects. Above treeline persistent slab avalanches 2-3' in depth will be possible to trigger on slopes where weak faceted snow sits above the late January crust. Additionally, triggering a wind slab 1-2' thick will be possible on lee sides of ridgelines and areas with prior wind loading. Along with the slab avalanche potential just mentioned, sluffing should be expected in the steeper terrain as well as possible cornice falls on ridgelines.


Primary Concern

Yesterday's avalanche activity:
There was one skier/snowboarder triggered wind slab avalanche just off of Tincan's Hippy Bowl ridgeline (photo below). Additionally, we had reports of three skier triggered persistent slab avalanches in the Eddies area (reported to have failed in weak snow above the January crust). We did not hear from too many folks in other areas despite many parties out enjoying the top-notch powder conditions right now.   **UPDATED at 8:20am - one additional observation was just sent in of a remotely triggered slab in Seattle Creek.

Primary Concern:
Now that the majority of the storm snow from Valentine's Day has settled out, the top 2-3' of the snowpack is mostly right-side-up (stronger snow under weaker snow) and composed of all February's storms. This would be great news if this layer did not rest on weak faceted snow with a uniform crust underneath - giving us a classic "persistent slab" problem. Katie Johnston (CNFAIC's 2014 Intern) and I were out yesterday on Tincan and had one of the largest collapses I have felt - ever. We put a hole in the snow to investigate and sure enough, found a 2" thick layer of facets to be the culprit - more details on this
HERE. Collapsing was also reported from Magnum yesterday in lower angle terrain.

The tricky part of our current persistent slab problem is we are not finding this weak layer of facets everywhere. Because of the variable distribution and lack of information in many areas, this slab/weak layer combo is guilty until proven innocent. These avalanches have been occurring in fairly small pockets so far but have the potential to be larger in bigger terrain. They also have the potential to be triggered remotely, from ridgelines or under slopes. Avoidance of steep (over 35 degree) upper elevation starting zones and cross loaded gullies will be the best management tactic related to the problem.


Our friends at the Utah Avalanche Center recently posted this great video on what a persistent slab problem is and why it can be so tricky. If you have 7 minutes it's a great watch.


Secondary Concern

Lingering wind slabs formed by the bump in Easterly wind on Friday may still be found today. Additionally, there could be a few areas with recent wind loading from a slight bump in wind last night. Keep an eye out for any area with old or new wind deposited snow. These wind slabs are likely to be 1-2' thick and predominantly on South and West aspects. They also have the potential to step-down and trigger a persistent slab which would create a larger and more dangerous avalanche.

Image: Human triggered wind slab off the Tincan ridgeline (3,400' SW facing - estimated 6-24" deep, 50' wide and running 300').
Human triggered wind slab off the Tincan ridgeline (3,400' SW facing).


Additional Concern

Cornices have been building, and falling, with February's stormy weather. One party saw a remote/natural cornice fall yesterday on the Magnum Ridge after another party walked by. This is good reminder to always give cornices a wide berth. Keep in mind they can also trigger an avalanche below.

Loose snow avalanches:
Sluffs are likely to be easily initiated in steep terrain at all elevations due to the loose surface snow and possible 1-3" of new light snow today.


Mountain Weather

During the past 24-hours we have seen partly cloudy skies with a few instability 'snow' showers. Around an inch of snow has accumulated since last night. Winds have been light to moderate from the East (average 10mph with gusts to 30mph). Temperatures have averaged around 10F at all elevations with valley bottoms dropping to the single digits this morning.

Today, another round of off-and-on light snow showers will be over us with 1-3" of snow possible. We may get a bit of visibility if we are lucky. Winds will be in the 10-15mph range from an Easterly direction on the ridgetops and temperatures look to rise to the low teens at the mid elevations and to ~10F on ridgetops.

The showery pattern that has been over us for the past several days looks to continue through tomorrow and clear up with mostly sunny skies Tuesday.

 

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
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