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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, March 16th 2018 6:11 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Today spring like conditions and above freezing temperatures have elevated the avalanche danger to HIGH across our forecast zone. Natural avalanches are anticipated and human triggered avalanches are likely on all aspects and elevations. Triggering a dangerous slab 2-5’ thick is very likely in avalanche terrain and natural wet loose and large slab avalanches are also likely today. The only way to manage this avalanche problem is by avoiding avalanche terrain, slopes steeper than 30 degrees and their runout zones.

A skier remotely triggered an avalanche on the skin track in Summit Lake Monday - see Saturday's Summit snowpack and avalanche summary and recent observations HERE.


 Show the Complete North American Avalanche Danger Scale
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.
Special Announcement

*Dangerous avalanche conditions are being seen region-wide. Recent human triggered and natural avalanches have been observed as far South as Lost Lake and North in Eagle River and Hatcher Pass.

**Roof avalanches are a serious concern today with warm temperatures, particularly around Girdwood where there is still a lot of snow on roofs. Be mindful of where children and pets are playing, vehicles parked and entrances to buildings in relation to loaded roofs.

 


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
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Possible
Unlikely

Chance

Historic
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Large
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Size

Spring time avalanche danger is upon us! Overnight temperatures remained above freezing below 1500’ and light rain has been falling in the lower elevation band. This is the first night without a freeze in the mid and lower elevations and today’s warming is expected to increase the danger. In the Alpine Easterly winds 15-45mph have been loading leeward slopes and adding stress to a very stressed out snowpack. Weak faceted snow is sitting 2-5’ below the surface and has proven to be very reactive this week. Everyday since Monday we've had reports of large human triggered avalanches across the region including Girdwood, Placer, Turnagain Pass, Lost Lake, Summit Lake and Grandview. Some natural avalanches have also released including an avalanche on a NE aspect of Skookum Valley with a crown almost a mile wide on Tuesday. Most of these avalanches have occurred below 3000’ and have been large enough to bury and kill a person. Some of these avalanches have been remotely triggered while others have released after the skier or snowmachiner was well onto the slope. So far we have not received any reports of anyone fully buried or injured, but several people have taken rides and deployed airbags this week. All avalanche terrain including smaller unsupported features and steep terrain in the trees are suspect. 

Three snowmachine triggered avalanches on Southerly aspects in Lost Lake on Wednesday that filled up a terrain trap with 20' of debris.  A big thanks to Leif Hagen for letting us share your photos and posting these on social media.

 

On Wednesday a skier-triggered avalanche caught and carried 3 skiers in small terrain on Silvertip (southern Turnagain Pass) on a NE aspect around 1500’. 

 

Yesterday a handful of skier triggered and remote triggered avalanches occurred in the Girdwood Valley of Notch Mountain. Its unknown if anyone was caught or carried. If you have any photos or info consider submitting an observation HERE. Reporting a near miss could save the life of others.

 


Avalanche Problem 2

Wet Loose

Almost Certain
Very Likely
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Unlikely

Chance

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Wet loose avalanches or roller balls today are indicative of solar radiation and/ or daily warming temperatures affecting change on the snowpack.  Wet loose avalanches could be small or large and have the potential to trigger larger, more dangerous slabs, particularly on southerly slopes greater than 30 degrees. We have been seeing this throughout the week and today it will be more likely if the sun pokes through the clouds.

 


Mountain Weather

Yesterday was overcast becoming obscured in the afternoon by rain and snow showers. Temperatures remained above freezing at 1000’ and light rain fell as high as 1500’ overnight. Two to four inches (.2” SWE) is estimated in the upper elevations. Easterly ridge top winds increased in the afternoon and evening to 15-45mph.    

Today skies are expected to remain overcast, but clouds may be thin allowing some sun through in the afternoon. Ridgetop winds will decrease this morning (5-20mph), but remain in the 30’s mph in the gap areas of Portage Valley. Scattered snow showers are possible in the morning with up to 1-2” of snow in the upper elevations. Rain/snow line is expected to remain around 1700’. Daily temperatures could rise into the low 40F’s by mid-day at sea level. Temperature in the upper elevations may reach the mid 30F’s this afternoon. 

Temperatures are expected to remain warm, but we may see freezing tonight if skies clear. Clear skies and sun are expected tomorrow and day time temps will be in the mid 30s and could increase into the 40F’s at sea level. Winds will be light and variable. Snow and rain showers may resume again on Sunday with an active pattern still in the forecast. There is talk of cooler temperatures returning to our area next week.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  .3  87 
Summit Lake (1400') 30  33 
Alyeska Mid (1700') 30   2 .26  81 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 22  ENE  15   44
Seattle Ridge(2400') 26  SE  20  52 

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 20, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: Open
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: Open
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: Open
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
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