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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 3rd 2018 4:33 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is CONSIDERABLE on all aspects and elevations above 1000'. A weak layer of snow has been overloaded by heavy snow, rain and strong winds over the past few days. Natural avalanches are still possible and human triggered slab avalanches are likely on slopes steeper than 30 degrees.  Remote triggered avalanches from below slopes, next to and above are also possible. Deep slab avalanches remain a concern above 3000'. Cautious route-finding and conservative decision-making are essential. 

Below 1000’, where little snow exists, the avalanche danger is MODERATE where an avalanche releasing from above could send debris through steep channeled terrain into this zone.


 Show the Complete North American Avalanche Danger Scale
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.
Special Announcement

Dangerous avalanche conditions are expected in the Southern Kenai Mountains (such as, Seward and Lost Lake) due to heavy snowfall.

Join CNFAIC Director Wendy Wagner TONIGHT, January 3rd from 7pm - 8:30 pm at the Blue & Gold Boardshop for a discussion on Understanding Weak Layers and the Current Snowpack at Turnagain Pass. 


Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Yesterday there was enough visibility to look around and see the evidence of a natural avalanche cycle in the advisory area. This confirmed that the new snow, strong winds and rain overloaded the weak layer of buried surface hoar and near surface facets. The connected slab avalanches on Eddies were the most notable in Turnagain Pass. The crowns extended along terrain features. Today any additional snow will add weight to the storm slab over the weak layer. Surface hoar and near surface facets are buried now by 1-3' of snow. Slopes that didn't avalanche naturally could now be teetering on the brink of failure just waiting for a human trigger. Conservative decision-making is essential today. Slopes harboring surface hoar and near surface facets may also be triggered remotely. 

There really is a smorgasbord or buffet of issues to consider if you decide to venture out today. Strong winds have loaded leeward aspects and potentially created winds slabs as well as growing cornices. At lower elevations if there is still saturated snow wet avalanches are possible in steep terrain. As temperatures cool these will be less likely and the crust that was noted to 2300' may have grown stouter and more supportable. The "railroad skiing"/ breakable crust will hopefully improve. In addition, pay attention to whether or not the new snow that falls to today bonds to the crust. 

Recent natural avalanches on Eddies. 

The buried surface hoar is the suspected weak layer and our layer of concern. 

 


Avalanche Problem 2

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

In the alpine, above 3,000’, the storms over the past few days have added additional load to slopes that already have a hard slab, 3-5+ feet thick, is sitting on top of weak sugary snow (basal facets) near the ground.  We have been talking about this for weeks now.  At these elevations, human triggered, large and dangerous deep slab avalanches ARE still possible. This is a high consequence avalanche problem that is impossible to outsmart and can take a long time to heal. Keep this in mind as improving visibility in the next few days may allow for travel to the Alpine. It is really important to remember that triggering an avalanche in the upper layers of the snowpack on may then initiate a deep slab avalanche. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below. 


Mountain Weather

Yesterday was mostly overcast with a few breaks in the cloud cover. There were rain and snow showers on and off throughout the day. Rain/snowline went as high as 2300' in the morning and then crept back down to around 1500'. Temperatures were in the mid to high 20Fs in the alpine, 30Fs at mid-elevations and 40Fs at sea level. Overnight the temperatures cooled a bit. Winds were easterly 15-25 mph gusting into the 50s, slowing down in the evening. 

Today will be mostly cloudy with rain and snow showers. Rain/snowline is forecasted to be around 800'. 1-5" of snow, .25 water is possible throughout the day.  Temperatures will be in the mid 30Fs to mid 20Fs. Winds will be light and variable. There is a chance of continued snow showers into the evening as temperatures cool into the teens. Skies will clear overnight. 

Thursday and Friday look to be clear and sunny with calm winds and temperatures in the 20Fs.  There is snow in the forecast for the weekend but the timing, amount and temperatures are still TBD. Stay tuned and keep thinking cold powder thoughts! 

*Seattle Ridge anemometer is rimed. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  35  rain .2  46
Summit Lake (1400')  33 rain .2 14 
Alyeska Mid (1700')  34 .5  1.5 36 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  25  62 
Seattle Ridge(2400') 28   *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: May 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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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