CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 18th 2017 5:44 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
Previous ForecastNext Forecast
BROUGHT TO YOU BY
The Bottom Line

The avalanche danger is MODERATE on the high elevations slopes (above 3,000') for the possibility of a slab avalanche breaking near the ground. Most concerning areas for triggering a large avalanche are where the snowpack is shallower, such as on the South side of Turnagain Pass and toward Summit Lake as well as the Crow Pass region. Additionally, a MODERATE danger exists for cornice breaks along ridgelines and lingering wind slabs at all elevations. 

*With forecasted sunny skies and fresh(ish) snow, please remember your safe travel practices! This includes, exposing one person at a time in avalanche terrain, watching your partners, being rescue ready and having an escape route planned.


 Show the Complete North American Avalanche Danger Scale
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.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

Two CNFAIC Fireside Chats coming up this week!  Both will discuss lessons learned from past avalanche incidents. We hope to see you there!


Avalanche Problem 1

It has been four days since the temperatures began cooling off and the extended wet storm cycles ended. It has been two days since the last snowfall. We are slowly getting a handle on the stability of the snowpack and a big thank you to all the folks that wrote in last night. We are most concerned with a known layer of faceted snow near and/or on the ground. This layer produced widespread human and natural avalanche activity during the beginning of December. The wet storms saturated the pack (and many of the facets) from 2,500' in elevation and below, which is now locked up into stable crusts. From 2,500' - ~3,000' the facets remain but several thick crusts in the slab are helping to stabilize the pack. The big question is, above 3,000' where the crusts disappear and facets under a hard slab may remain. Stability tests so far have been done up to 3,300' and all signs point to a strong snowpack and no reactivity in the facets. See video below. This is promising. But, we must be vigilant and conservative this week as we explore the higher elevations.

Things to keep in mind:
    - 
Triggering a dangerous deep slab avalanche is possible above 3,000'
    - Shallow snowpack areas are most concerning (more trigger points and possibly more reactive facets). For instance, South end of Turnagain Pass, Crow Pass, Summit Lake
    - No red flags likely to be present to indicate an unstable pack
 

 

Pictured below is the North side of Magnum Ridge showing wind scouring and a thin snowpack. The top portion pokes into the elevation band we are concerned about. 

 
-


Avalanche Problem 2

The other set of avalanches problems we are still assessing are old wind slabs, cornices and sluffing. These are surface instabilities and much easier to see and assess. So far we have found good bonding with Friday's new snow as wind slabs seem quite stubborn. However, we have only had information for a small amount of terrain. Keep an eye out for cracking in the snow around you, hollow feeling snow and stiff snow over softer snow. In most places under 2,500' there is crust underneath, watch for area where the Friday's snow is not bonding to this crust. 

 The SW face of Sunburst. Old avalanche debris is covered by 8" or so of new snow from Friday, Dec 15th. 


-


Mountain Weather

Partly cloudy skies were over the forecast area yesterday. During the past 48-hours there has been no precipitation. During the past 24-hours winds have been light from the East and North and temperatures in the mid 20's at most locations. Overnight, an inversion has set in and valley bottoms are in the low teens while ridgelines are in the upper teens.

Today, we can expect a mostly sunny day. Ridgetop winds are forecast to remain light, 5-10mph from a Northerly direction and switch to Easterly tonight, remaining light. Temperatures in valley bottoms should climb during the day to the mid 20'sF while ridgetops remain in the low teens. 

Tuesday, another round of snow is headed our way as a bearing low pushes a front over Southcentral. This system looks to be cold enough for snow close to sea level, it also should favor Anchorage, Hatcher Pass and bring a several inch refresh to our neighborhood in Turnagain Pass. Make sure and check tomorrow's advisory!

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24  33 
Summit Lake (1400') 25  27 
Alyeska Mid (1700')  18 10 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') *n/a  *n/a   *n/a   *n/a  
Seattle Ridge(2400') 22  SE 

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
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC