CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Sunday, February 5th 2017
Created: Feb 5th 6:09 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
Alaska Mining and Diving Supply
Special Announcement

The Southern Kenai Mountains including Seward, Snug Harbor and Lost Lake continue to have an unstable snowpack. 
Human triggered large avalanches, breaking near the ground, are possible. 
Please see link above for recent activity. Another 1-2' of wet heavy snow fell Tuesday and Wednesday, adding more load to a snowpack with weak snow near the base. Keep in mind avalanches can be triggered remotely, from below or mid-slopeCareful snowpack evaluation and cautious route-finding is essential. 

Hatcher Pass avalanche conditions: If you are considering heading this way - please check the recent observations for Hatcher Pass and the Saturday morning advisory!


The Bottom Line

The avalanche danger is MODERATE in the advisory area including both Turnagain Pass and Girdwood Valley. Above 1000’ triggering a persistent slab avalanche 2-4+ feet deep is possible and consequences remain high should you find a trigger spot. Two large snowmachine triggered avalanches occured as recently as Friday and both folks involved were uninjured. Heat from the sun will also be something to monitor and could make wind slabs, cornices and loose snow avalanches more tender. Be sure to carry your rescue gear and practice safe travel protocol - such as exposing one person at a time, grouping up in safe zones, having escape routes planned and watching your partners!  

Below 1000’ the danger is LOW, where temperatures are freezing overnight and a hard crust exists. 

Summit Lake: An unstable snowpack exists in the Summit Lake area and human triggered avalanches breaking near the ground are possible. Make sure and check the Saturday Summit Summary HERE.


Primary Concern

Friday there were two large snowmachine triggered avalanches in our advisory area. One in Seattle Creek where a rider was completely buried except for his hand sticking out.  He was quickly rescued by his party but his sled was not located. In Lynx Creek a snowmachiner triggered a slope just after he crested the hill but was not caught. One of his partners commented, “If I had tried high-marking at the same time as him or right after him I would not have made it outta there.” No obvious signs of instability were observed and in both cases there was already tracks on the slope. 

Both of these avalanches were triggered on an old/weak foundation, facets near the ground. This upside down structure exists in many places across our forecast zone, but not everywhere. Due to the spacial variability of our current snowpack assessing the snow that is across an entire slope is difficult and near impossible. Many folks have been able to snowmachine or ski/ride on a variety of steep terrain without incident over the last few days. This speaks to the uncertainty of our current avalanche problem and the dangers of a stabilizing snowpack. The likelihood of triggering a deep persistent slab is decreasing, but the consiquences remain high should you find the wrong spot. The slab in Seattle Creek was reported to be 4-6' deep and the avalanche in Lynx 1-3' deep. This type of avalanche is often triggered in a thin part of the slab, near rocks or on the edge of the slab. These can also be triggered by multiple skiers/boarders and/or snowmachines on, near or under slopes. Remember just because the slope has lots of tracks does not mean the slope is safe. It may be the 3rd or 10th or 25th track that tips the balance. Above freezing temperatures in the Alpine and direct sunshine may also make these slabs easier to initiate.  This is a lot to factor into decision making this weekend, but please keep the following in mind: 

  1. An avalanche on a large open slope may propagate and run further than expected.
  2. Obvious signs like shooting cracks or collapsing “whumpfing” are unlikely today.
  3. Identify safe zones and travel one at a time between islands of safety.
  4. Make a plan and reasses with your partners as you travel. Radios can be very helpful.
  5. Be aware of other groups and if an area becomes too crowded it may not be possible to practice safe travel protocol. Consider going elsewhere. 

Seattle Creek Avalanche that occured on Friday, Feb.3 near the -3 bowl on a NE aspect. Photo courtesy of Brad Larson

 

This crown in Lynx Creek wraps around the ridge on a Northeast facing slope. Notice the vegitation and places where the ground is exposed. Photo by Mahear Aboueid

 

 

The crown of the Lynx Creek avalanche can be seen easily from the Johnson Pass trail head and shows the bigger view of the crown as it wraps around the slope. 

 


Additional Concern

In addition to deep persistent slab avalanches there are a few other avalanche concerns to pay attention to today. The sun is out and affecting the snow in terrain on the Southern half of the compass. Warm temperatures and direct sunlight may also play a factor in all of these concerns. Pay attention to changing conditions!

Wind Slabs: Old stubborn wind slabs as well as some newer ones may be triggered on leeward slopes. Look out for pillowed or drifted snow, listened for hollow sounds and avoid areas with stiff snow over soft snow. Warming temperatures and direct sunlight may make these slabs easier to trigger on solar aspects.

Loose snow: With 4-8" of loose snow on the surface over a dense base, watch your sluffs and watch how the sun is affecting the snow around you. These may pack enough punch to push you somewhere you don't want to go i.e. a terrain trap. 

Cornices: Yesterday large cracks were reported along the some of the cornices in the back bowls of Seattle Ridge. Cornces are unpredictable hazards and can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give ridge lines extra space - they may have a cornice on the other side. 

Sun triggered roller balls were observed on many South and East facing slopes. 


Mountain Weather

Yesterday a strong inversion caused ridgetop temperatures to reach a high of 43F during the heat of the day and pockets of cold air in valley bottoms were in the single digits. Winds were calm and variable. No precipitation has been recorded in many days.  Overnight ridgetop temperatures have been slowly dropping, but are still hovering around 32F. 

Today the inversion will start to weaken, but upper elevation temps could easily reach the mid 30F’s by mid day. Expect sunny and clear skies with light and variable winds. Over the next few days an arctic air mass is forecasted to shift south over Southcental, Alaska with a chance for single digits later in the week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29  53 
Summit Lake (1400') 17  23 
Alyeska Mid (1700')  29 47 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 39  var.  12 
Seattle Ridge(2400') 36  var. 

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: Mar 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
Skookum Drainage: OpenSKOOKUM DRAINAGE CLOSES TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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