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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Saturday, February 4th 2017
Created: Feb 4th 4:18 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.
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BP Alaska
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. 

Placer and Twenty Mile: Travel is extremely difficult right now due to recent rain, warm temperatures and overflow. This area will remain open in anticipation of forecasted cooler temps but travel is NOT currently recommended for novice riders.

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. Above 1000’ on slopes over 30 degrees, triggering a persistent slab avalanche 2-4+ feet deep is possible and consequences remain high should you find the right trigger spot. 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

Yesterday the weak facets near the base of the snowpack showed their teeth and two snowmachiners had very close calls.  On the Seattle Creek Headwall a slope (that had been previously high marked and skied) was triggered just as the as snowmachiner that climbed it turned to travel back down. The rider tried to pull his airbag but was unsuccessful and was completely buried except for a 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. Snowmachiners in both locations remarked that there were no signs that the snowpack was unstable and in both cases there was already tracks on the slope. Many other skiers and riders enjoyed the mountains yesterday without incident. All these factors are characteristic of deep persistent slab, low probability of triggering but high consequences if you do 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. It may be the 3rd or 10th or 25th track that tips the balance. Observers have found weak faceted snow at the base of the snowpack across the area from Seward to Girdwood. However, another tricky part of the equation is that although this set-up is fairly widespread it is also variable making some slopes safe to ride and others very dangerous. The take away from the avalanches yesterday is that weak snow with a deep slab on top is poor snowpack structure and may remain suspect for days to come. Temperatures above freezing in the Alpine and direct sunshine may also make these slabs more easy to initiate.  All of this has to be a factor in decision making this weekend.  Remember signs of instability are not always present and slabs may break once you are well out onto them. As always practice safe travel protocols, be aware of other parties in the area, choose terrain wisely, carry rescue equipment and don't let the sunshine cloud your judgment. 

Seattle Creek avalanche. Photos: Chad Aurentz

Lynx Creek avalanche. Photos: Mark Guess

Snowpack near the Lynx Creek avalanche shows hard snow over soft weak snow near the ground. Photo: Travis Rupp

 


Additional Concern

In addition to deep persistent slab avalanches there are a few other avalanche concerns to pay attention to today. All of these concerns could be a hazard seperately or once initiated, trigger a larger persistent slab deeper in the snowpack. Warm temperatures and direct sunlight may also play a factor in all of these concerns. We have reached the time of year. The sun is out and affecting the snow in terrain on the Southern half of the compass. A small crust was observed forming on Thurday on steep southerly slopes. Pay attention to changing conditions!

Wind Slabs: Old stubborn wind slabs may be triggered on leeward slopes. Looked 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.

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: Give cornices wide berth, avoid travel on slopes below them and remember they can break farther back onto the ridge than expected.  If cornices do break and fall they could trigger an avalanche on the slope below. 


Mountain Weather

Yesterday was warm in the Alpine with temperatures reaching the 40Fs on some weather stations. Skies were clear and winds were light and variable. Valley fog moved out in the mid morning. Overnight the inversion kept temperatures cold in the valley bottoms with some areas seeing teens and single digits. Temperatures in stayed above freezing at higher elevations.

Today will be warm, temperatures are already in the 40s in the Alpine. Skies will be mostly clear and winds will be calm. The weather looks to be similar into early next week as a "high latitude blocking pattern remains firmly entrenched over mainland Alaska." Cooler temperatures and a chance for precipitation are a possibility by mid week! Stay tuned. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 25   0 54 
Summit Lake (1400') 14   0  0  23
Alyeska Mid (1700')  23  0  0 48 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  39  ENE  5 11 
Seattle Ridge(2400')  31  variable  3  7

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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