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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Saturday, March 7th 2015
Created: Mar 7th 6:47 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
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The Bottom Line

The avalanche danger is generally LOW and will rise to MODERATE in the Alpine late in the day.  Fresh shallow slabs up to 10” in depth could be triggered on steep leeward slopes.  Low volume sluffing is also possible in steep terrain in the higher elevations today.

The danger is LOW in the Treeline elevations, where avalanches are unlikely.


Primary Concern

Issues directly related to new storm snow will be at the forefront of our avalanche concerns today.

4” of snow overnight combined with another 3-4” today will help to build small slabs in the Alpine.  These slabs will be thicker on leeward slopes and require terrain at least 35 degrees in steepness to trigger.  Bonding of these slabs will be generally good as the current storm progression is going from warm to cold, laying down “right side up” slabs.  The exception to this will be in isolated pockets on steep leeward slopes.  It is in this terrain where wind slabs could become as thick as 10” by the end of the day.  Avoid slabs in this terrain that sound hollow, are "punchy", or produce shooting cracks.

Low volume sluffing will be possible in very steep terrain (over 40 degrees).  These should be slow moving and easy to avoid.  Sluffs will be dry above 3,000’ and gradually more damp as you lose elevation.  Heightened awareness of sluffing will be important when traveling above or towards terrain traps such as gullies, cliffs and trees.


Secondary Concern

Weak layers buried 1-2’ deep seem to be dormant for the most part around Turnagain Pass.  More uncertainty exists in the Girdwood Valley where we have less information about this layer.  Yesterday my partner and I had a good look at the late January facet layer in steep Alpine terrain and found it to be unreactive.  Testing over the past week has been consistent with what we found.  New snow will not be enough of a load to awake this layer today.  However, the possibility still exists to trigger slabs in the 2 foot range in isolated pockets in very steep (over 40 degrees) terrain.  Focused assessment of this layer will be important if you find yourself venturing into steep Alpine terrain.


Mountain Weather

Warm air continued its chokehold on the region over the past 24 hours.  Temperatures have begun to dip slightly in the early morning hours with freezing levels around 1,000’.  Moisture associated with a large system moving in from the Southwest has brought light amounts of snow with the Center Ridge SNOTEL recording 4”/.4 H20 and Alyeska Midway station with 3.7”/.3”H20.  Ridgetop winds have been light to moderate out of the East.

Today we can expect to squeeze another 3-4” of snow/.3” of H20 out of this system.  Ridegtop winds will be out of the Southeast at 15 to 20 mph.  Rain/snow line will be around the 1,000’ level and slowly drop to 500’ by the evening hours.

The extended outlook is showing a gradual clearing and cooling trend.  Precipitation will linger through the weekend with clear skies and daytime highs in the teens by the beginning of next week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33 4 .4 44
Summit Lake (1400') 36 trace .1 7
Alyeska Mid (1700') 34 4 .3 25

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 26 E 10 31
Seattle Ridge(2400') 27 n/a 16 32

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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