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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, December 29th 2014
Created: Dec 29th 6:33 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The avalanche danger is CONSIDERABLE in the alpine today.  Wind slabs building into the 12-16” range could release naturally and will become increasingly sensitive to human triggers as the day progresses.  The trend for instability will be on the rise throughout the day.

It will be possible for avalanches originating in the higher elevations to run into the lower elevations today.  Because of this the avalanche danger is MODERATE at and below treeline.  Human triggered wind slabs up to a foot in depth will also be possible in the treeline elevations. 

Avoid steep leeward slopes in elevations where new snow and wind is actively forming fresh wind slabs.  Avoid being in the runout of terrain that is above you.


Primary Concern

High ridge top winds, in the 40 mph range have been blowing out of the East since yesterday morning.  While the amount of snow available for transport has been minimal (in the 2-4” range) slabs have been forming and rapidly loading leeward slopes.  Due to the rapid nature of this loading, natural avalanches are possible today. When winds are at these speeds, slabs tend to form lower down on slopes and in a more scattered pattern.  Because of this it becomes possible to travel through starting zones without being on a wind slab only to find yourself on top of unstable snow part way down.   

Fortunately the weather today will make getting into starting zones very difficult, as poor visibility will make travel challenging in the alpine.  Despite this, should you find yourself in upper elevation terrain be on the lookout for signs of wind loaded snow.  Shooting cracks will be the first indicator that the snow below your feet is unstable.  Snow that has an upside down feel to it, is stiff and is on the leeward side of slopes or along cross loaded gullies should be avoided today. 

Expert level terrain assessment skills will be necessary for travel in the mountains today, as avalanches have the potential to release naturally and run through multiple elevation bands.


Secondary Concern

In the back of our mind today are persistent slabs.  Weak snow 2 feet below the surface is present in the snowpack.  From Turnagain Pass down to Summit Lake that layer is widespread buried surface hoar.  In the Girdwood Valley that layer is in the form of facets and exists in pockets.  Several skier triggered avalanches have occurred over the past 2 weeks on these layers and are worth keeping in mind when out in the mountains today.  

The buried surface hoar on Turnagain has quieted down for the time being.  Skiers in the Girdwood Valley triggered an avalanche on Saturday on a steep upper elevation slope with a thin snowpack.  Avalanches occurring in the new snow have the potential to step down to these deeper layers.  Because of this it will be possible for avalanches to increase in volume; avalanches occuring within the new snow could pull out deeper slabs and be large enough to injure and bury a person.

 


Mountain Weather

Yesterday ushered in winds in the 40 mph range out of the East.  Temperatures have been creeping up into the low 30s at 1,000’.  Rain at sea level began overnight.  Snow has been falling above 1,500’ with the Center Ridge SNOTEL showing 3” of accumulation in the past 24 hours.

Today expect a continuation of this pattern - warm, wet, and windy.  Temperatures will remain in the low 30s at 1,000’, ridge top winds will be out of the East at 40 mph, and  2-6” of snow will fall in the higher elevations.  The rain snow line should hover around the 1,000-1,500’ elevation through the day.

The plume of moisture moving over us will continue to pull warm air from the South.  We should expect to see continued snow and rain, high winds and mild temperatures through Tuesday.

Alaska DOT has the Turnagain Pass Weather station back up and running.  This is a great resource for checking weather info and webcams at road level (1,000’).

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31 3 .3 31
Summit Lake (1400') 34 0 .1 6
Alyeska Mid (1700') 31 2 .3 23.6

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23 E 35 87
Seattle Ridge(2400') 24 SE 37 77

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.

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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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