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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, April 9th 2018 5:25 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Warm weather conditions are keeping the avalanche danger MODERATE for wet loose avalanches and the chance for a slab avalanche. Wet loose avalanches will be possible to trigger on steep slopes facing South, East and Westerly. Triggering a slab avalanche 1-2' thick remains possible on Northerly aspects where soft dry snow exists. Watch for cornices and give them a wide berth.


 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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The sunshine that has been heating up the snowpack the past several days has been replaced with cloudy, warm and windy weather. Instead of cooling off and freezing overnight, the clouds have kept the heat in. This morning, temperatures sit near 40F below 1,500' and much of the wet surface snow from yesterday has likely seen very little re-freeze. To add to this, light rain could fall up to 2,500' today. Although the snowpack has been slow to undergo the springtime transition this year, the warm and cloudy weather today and tomorrow may start to push it over the edge. What this means is we could start seeing larger wet snow avalanches - something to keep in mind moving forward into the middle of April. 

Wet loose avalanches:  We have seen several small wet loose slides composed of last Wednesday's storm snow over the past several days. Today, these are possible again and most likely in the mid-elevation band where the temperatures are warmer. Triggering one of these is possible on steep slopes with wet and saturated surface snow (East, West and South facing). The rule of thumb is, if you find yourself in saturated snow up to your boot tops, it's time to head to lower slope angles or a different aspect with a drier snow surface.

Wet slab avalanches:  We have not seen any wet slab avalanche activity, but it's not out of the question a wet loose slide could trigger a wet slab today/tomorrow.

 
Recent wet loose avalanches on South facing Magnum Ridge (photo Allen Dahl).

 

Roller balls on Magnum's Northerly face. These occurred yesterday and a sign Northerly aspects are beginning to warm. Roller balls are also a sign that wet loose avalanches are possible.


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Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Triggering a slab avalanche 1-2' thick in the dry/moist snow on North shaded aspects is becoming more unlikely, but still possible. These slopes that harbored soft settled powder yesterday will become moister today. This change in surface character can add to instability in areas Wednesday's storm snow has yet to bond well with the underlying surface. Most slopes are showing good bonding, yet we know there are areas with a facet/crust combination under the storm snow that keeps this concern in our minds.

 Old storm slab on a Northerly aspect in Seattle Ck drainage (Main Bowl/1st Bowl) from last Thursday. Despite the initially poor bonding with the new/old snow last week, the snowpack was showing signs of good bonding now. 


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Additional Concern

Cornice

It's that time of year where the snowpack is slowly warming up and cornices will begin to break. We can't let ourselves get complacent when traveling along ridgelines - give these guys a wide berth.

Large cornice that forms yearly over Zero (Momma's) Bowl at the top of the up-track on Seattle Ridge. It's easy to get lured into thinking we are over ground when in fact we may be over only snow and air.


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Mountain Weather

Partly cloudy skies were seen over the region yesterday before becoming mostly cloudy overnight. Ridgetop winds over the past 24-hours have been Easterly in the 10-15mph range. Temperatures rose to 50F below 1,000' and up to the mid 30'sF along ridgetops. Overnight, clouds have kept temperatures warm and most elevations are reporting temperatures in the 30-40F range. No precipitation was recorded. 

For today, a warm and windy day is on tap due to a low-pressure system in the Gulf ushering warm moist air our way. Light rain up to 2,000-2,500' is expected with wet snow above this. Precipitation amounts expected are small, .2-.4" of rain and 2-4" of snow by tomorrow morning. Ridgetop winds will remain Easterly and increase to the 15-25mph range with stronger gusts. Temperatures will stay in the 40-50F range in valley bottoms and near 32F along ridgetops. 

Tomorrow, Tuesday, continued cloudy, warm and windy weather will remain before the low-pressure system slowly moves South allowing cooler and possibly drier air for Wednesday into Thursday. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 40  77 
Summit Lake (1400') 41  32 
Alyeska Mid (1700') 40  74 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 31  NE  12  34 
Seattle Ridge(2400') 35  SE  15  36 

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 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
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: ClosedClosed as of 4/27
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
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