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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, February 16th 2015
Created: Feb 16th 6:43 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The avalanche danger is HIGH in the Alpine elevations (above 2,500’) today, where dense slabs up to 3’ in depth have the potential to release naturally.  The danger is CONSIDERABLE in the Treeline elevations (1,000-2,500’) where avalanches releasing from above have the potential to run into this lower elevation band.

Travel in and below avalanche terrain is not recommended today.


Primary Concern

New snow and wind have combined to create very unstable slabs in the 8-12” range.  Ridgetop winds have picked up into the 40 mph range out of the East/Southeast overnight and will remain strong through the day.  An additional 10-12” of snow and, more importantly, 1” of H20 forecasted for the higher elevations will increase the size of these slabs into the 2 foot range.  These slabs will release naturally in some locations and will be very sensitive to human triggers.  Rapid loading that occurred overnight and will continue throughout the day is enough of a trigger to initiate avalanches.

This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” this problem today.


Secondary Concern

A layer of weak snow that sits anywhere from 8” to 3 feet below the surface is the most concerning layer today.  Avalanches occurring in the upper layers have the potential to step down to this layer.  In cases where this happens, the volume will be large and potential for burial, if caught, is high.  Avalanches occurring at this layer have a high propagation potential, which means that fractures can and will travel across slopes and over long distances.  

Because of this travel in avalanche terrain is not recommended today (have I mentioned that already?).  While this problem exists mainly in the Alpine elevations, it will be important to avoid the runout of terrain from above when traveling in the Treeline elevations.


Additional Concern

Rain falling on snow as high as 2,000’ will weaken the surface snow.  This will result mainly in wet loose avalanches.  Volume will be generally low, as the snow in the mid and lower elevations has already been hit with periods of rain over the past few days and has had time to adjust.  With that being said, it will be important to avoid steep terrain where the surface snow is wet.  If you find yourself sinking through the snow deeper than your boot it is time to move to lower angled terrain.  Consequences of wet loose surface snow moving will become high if pushed into or over terrain traps such as cliffs, gullies, glide cracks, or trees.


Mountain Weather

Yesterday brought a continuation of warm, wet and windy weather to the area.  Temperatures were in the mid 20s F along ridgetops.  Temps at sea level climbed into the high 30s - low 40s F.  A mix of rain and snow have been falling with the Center Ridge SNOTEL site picking up 5” of snow containing .5” of H20.  The rain/snow line fluctuated and was around the 1,800’ mark for most of the 24 hour period.  Winds cranked back up with Sunburst averaging in the 30 mph range with a max gust of 96 mph.

A strong surface low currently parked just south of the Alaska Peninsula is pulling a warm stream of moisture from the South over the area.  Today will bring intense periods of precipitation and high winds, with an additional 10-12” of snow and 1” of H20 above the rain/snow line.  The rain/snow line should be around the 1,600’ mark.  Winds will be strong out of the East at 40-50 mph.  Temperatures will remain warm with ridgetops approaching 30 degrees F.

Wind and precipitation intensity should begin to taper off by tonight.  Temperatures will cool slightly and a chance for showery precip will remain through the middle of the week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33 5 .5 39
Summit Lake (1400') 36 rain .1 9
Alyeska Mid (1700') 33 2/rain .4 27

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25 E 31 95
Seattle Ridge(2400') 27 SSE 27 63

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: Mar 25, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
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: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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