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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, March 30th 2018 5:08 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger continues to be MODERATE above 1500’ in the periphery of the forecast zone, such as Girdwood Valley and South of Turnagain Pass. Triggering a hard slab avalanche 2-4 feet thick remains a possibility and may be triggered remotely. A generally LOW danger exists in the core zone of Turnagain Pass where triggering this type of avalanche is trending toward unlikely. Pay attention to afternoon warming and give cornices a wide berth. 

Similar avalanche concerns exist in the Summit Lake area and other zones on the Kenai.


 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
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Size

As the days go by with little in the way of weather to contribute to avalanche danger, the chances for triggering an avalanche are decreasing. It has been over two weeks since the last snowfall, a week since the last human triggered avalanche and the snowpack is adjusting to the weak layers that sit in the middle and base of the snowpack. Terrain in the core Turnagain Pass zone is trending towards a LOW danger, meaning triggering a slab avalanche is unlikely - but not out of the question. Areas on the periphery, such as Girdwood Valley and the South end of the Pass towards Johnson and Lynx, we are more concerned with as they have a thinner snowpack and poorer structure.

Yesterday a large collapse was triggered under Goat Mountain in the Girdwood Valley (see Heather's video below). This is a sign the snowpack can still produce a dangerous slab avalanche. The slabs in questions are hard slabs 2-4' thick. The weak layers in question were formed in January and are various layers of facets and buried surface hoarThough these layers are becoming harder and harder to trigger, there is still a chance someone could hit the wrong spot. This is a low probability, high consequence situation and makes travel in avalanche terrain tricky. No obvious signs of instability may be present before a slope releases and it may be the 10th skier or snowmachiner onto a slope that finds the trigger point. These trigger points are often in thinner areas of the snowpack near rocks or in scoured areas along ridges. 

Sunshine:
If the sun shines in full force today be aware of warming later in the day on Southerly slopes. Especially steep southerly slopes with rocks that will help heat up the snow around them, aiding in possible wet avalanche activity. As we gear up for a weekend of sunny skies, keep the afternoon warming on your radar!

 

 Poor snowpack structure and poor pit results found in the Girdwood Valley yesterday. This video was taken in Gulch Creek under Goat Mountain near 3,000'.

 

A loot at Turnagain Pass from the top of the uptrack on Tuesday. It has been over two weeks since snowfall and surfaces are hard and crusty from either the sun, wind or both.


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Additional Concern

Cornice

Cornices are large in many places. As we head into warmer, sunnier weather remember this can help de-stabilize them. As always, give cornices plenty of space and limit exposure underneath them.


Mountain Weather

Partly cloudy skies were over the region yesterday. A few snow flurries were seen in the morning but no snow accumulated at Turnagain Pass. A few inches were found in the upper Girdwood Valley. Ridgetop winds have been light from the North and West during the past 24 hours (5-10mph). Temperatures were in the teens yesterday along ridgetops and in the mid 30'sF in valley bottoms. Overnight, valley bottom temperatures have cooled slightly to 25-30F. 

Today, Friday, partly cloudy skies this morning should give way to mostly sunny skies this afternoon as high pressure has built in over our area. Ridgetop winds look to remain light from the North in the 5-10mph range. Temperatures are expected to stay in the teens along ridgetops and warm to the mid 30'sF again at 1,000'. 

For the weekend, we can expect high pressure to remain, which will bring mostly sunny skies and Northerly winds. Cool temperatures look to stay in place for Saturday, but warmer a air mass may push in Sunday or Monday. This could bring more spring-like conditions.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  27 76 
Summit Lake (1400') 28  31 
Alyeska Mid (1700') 27  72 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 17  12 
Seattle Ridge(2400') 24  NW  23 

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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