CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Monday, April 3rd 2017
Created: Apr 3rd 5:38 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

A reminder that Skookum Valley is closed to motorized use as of yesterday, Saturday, April 1st. This is an annual closure as per the Chugach National Forest Plan document. All other motorized areas remain open - see area status on the bottom of this page for more information.


The Bottom Line

The avalanche danger remains HIGH at all elevations due to strong winds, rain and snowfall in Turnagain Pass, Portage, Placer and Girdwood where natural avalanches 2-5’ thick are likely today. Travel is not recommended in avalanche terrain where natural avalanches are likely occurring and human triggered avalanches are very likely. Steer clear of gullies and the bottom of large and steep slopes in the event an avalanche releases above you.

Hiking in Portage ValleyTravel along, and past, the designated Byron Glacier trail is not recommended due to exposure to avalanche terrain. Natural avalanches are possible today that could send debris to valley floors.

Summit Lake: Travel in avalanche terrain is not recommended. Read the Saturday Summit Summary HERE including an avalanche triggered yesterday at Manitoba, HERE.


Primary Concern

Today marks one week of elevated avalanche danger due to continuous stormy weather following a cold and dry March. A fast moving warm front will impact Southcentral, Alaska this morning, causing Easterly ridgetop winds to build into the 40’s (mph) with gusts in the 60’s (mph). Up to 6” of snow is forecasted to fall above 2000’; this is .45” of rain at lower elevations. Natural wind slab avalanches up to 1-2’ thick are likely today in the alpine due to blowing snow overloading steep slopes.This is on top of 2-4' of snow that has incrementally fallen across our region over the last week. These storm related wind slabs have the potential to step down to an older layer in the snowpack, and run further than expected. (More on this below.) Avoiding all avalanche terrain, slopes steeper than 30 degrees, is the only way to manage this problem today. This includes giving run out zone plenty of space, and avoiding trails like Johnson Pass and Lynx Creek, where an avalanche could cross the trail. 

One of the many debris piles along the East face of Seattle Ridge over the last few days. This is a good example of how far things have been running in Turnagain, and reminder that today's strong winds could be creating bigger slabs - increasing their run out distance. 


Secondary Concern

On Saturday rain falling on dry snow caused a cycle of wet slab avalanches below 1500’. Over the last two days an additional 6-12” of snow fell across our region insulating a layer of wet snow. Today another cycle of rain, up to a half an inch of water is forecasted below 2000’. This is a perfect recipe (rain falling on dry snow) to intiate another round of natural wet avalanche activity. To compound this, an avalanche in the alpine has the potential to run into the lower elevation band and intiate a wet slab avalanches - increasing the overall volume.  Again it will be important to avoid steep terrain and maintain a conservative distance from all runout zones. 

A wet slab that occurred between 1 and 2pm on Eddies on Saturday, 4/1/17. It was roughly 1-2' thick and 300' wide. The crown is near ~1500' and was triggered by rain on the new snow from this week. However, if you look closely, it almost seems like it could have broken in an old weak layer that was not near the top of the pack. Photo by Wendy Wagner. 

 

 

Snowpit at 1500' yesterday on Sunburst shows about 3" of wet saturated snow perserved below yesterday's new snow. 

 


Additional Concern

Several old layers of weak snow (near surface facets and surface hoar) sit buried in the snowpack. Avalanches releasing in the storm snow have the potential to 'step down' into them. Snowpack tests are still showing propagation potential in these layers and today's strong winds and precipitation are likely to tip in the balanche in the upper elevations. An avalanche occuring in one of these older layers could be as deep as 3-5', and run the entire length of slide path. 

 

 

 

A persistent slab avalanche triggered by a skier on Manitoba yesterday in Summit Lake. Luckily no one was cuaght or injured. Photo by Matteo Calcamuggi

  

A snowpit at Sunburst yesteday shows several weak layers (buried surface hoar and the March facets) that are sitting under this week's snow. Snow totals in the alpine are estimated to be closer to 3-4' where the snow has remained dry.

 


Mountain Weather

Yesterday rain/snow line moved from 200’ to 700’ late afternoon with daily warming. Scattered showers dropped an additional .4” of H20 fell, 4” of snow, along Turnagain Pass. Daytime temperatures reached a high of 41F mid day at Center ridge weather station. Skies were obscured and ridge top winds averaged around 20mph from the East. Overnight temps cooled to freezing, causing light rain to become snow again at sea level.

Today a warm front extending from a low pressure system in the Gulf of Alaska is quickly approaching South-central Alaska. Easterly ridge top wind are expected to build this morning from 20mph to 40mph by early afternoon, gusts could reach the 60mph’s. Warming temperatures will cause rain at lower elevations today and rain/snow line may reach 2000’ my mid day. Rain and snow showers are expected to pick up intensity by late afternoon, and a total of .45” of water is expected by 6pm. 

Tonight precipitation should intensify, with an additional 1” of H20 forecasted. Warm temperatures will likely keep precip as rain below 1000’ overnight. Strong Easterly winds are expected to last through tomorrow morning. Expect a similar pattern of low pressure systems to continue to impact our region through the week. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 34  0.4  75 
Summit Lake (1400') 33  29 
Alyeska Mid (1700') 31  0.28  75 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 21 ENE  18  47 
Seattle Ridge(2400') 26  rimed   rimed  rimed  

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