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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Thursday, March 28th 2013
Created: Mar 28th 6:52 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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The Bottom Line

A MODERATE danger rating exists again today above treeline where shallow slabs yesterday proved quite easy to trigger on a variety of bed surfaces.  Expect these slabs to build in thickness today, as light density snow from Monday’s storm will be easily transportable under SE winds forecasted to be in the 30 to 45mph range.  If snowfall amounts exceed 6” during the day, with forecasted winds the avalanche danger will very likely increase to CONSIDERABLE by days end. 


Primary Concern

In the Turnagain pass zone yesterday my partner and I found shallow soft wind slabs (6-10” deep) that were easy to trigger in terrain greater than ~38 degrees.  This problem was shown to be quite manageable yesterday as these slabs were all small and relatively predictable.  Today is going to be an entirely different ball game as SE winds and new snow will build these slabs to ‘unmanageable’.  Slabs are sitting on a variety of crusts and stiff wind board on south, east and west aspects; all exhibit attributes of a slick bed surfaces.  To top it off, there do still exist pockets of facets acting as a weak layer from our prolonged mid-March sunny spell.  It’ll be wise to pay particular attention to leeward facing slopes and cross-loaded gullies, as this is where you’ll find deeper, wind loaded pockets ripe for a trigger today.  Pay attention to indicator slopes and/ or try and test the snow on smaller test slopes prior to committing to bigger or steeper terrain.

                              Shallow, easily triggerable wind slab yesterday.

 


Secondary Concern

With plenty of snow available for transport, moderate winds today and increasing temperatures on the horizon I think cornices warrant a brief discussion.  It’s been several weeks since we’ve seen a cornice fall so what this tells me is that they are continuing to grow and ripen as we near April 1st.  Cornices are nearly impossible to forecast for so what we can do is mitigate this hazard by reducing time spent below a cornices and travel well back from the roof of a cornice.  There are some enormous cornices in the backcountry right now and inevitably many of them will fail in the last month or so of our season.  Play it safe and avoid these backcountry bombs!


Mountain Weather

Temperatures warmed substantially yesterday from single digits to the low 20’s at 1000’ as we watched the approach of high clouds stream into south-central.  Southeast winds in the 30-45 mph range look to be the biggest game changer today as a warm front advances through the Gulf of Alaska and into our region.   Snowfall amounts throughout the day are expected to be in the 2-6” range with temperatures in the low 30’s, meaning mostly snow at sea level.  Overnight, winds and precip are expected to increase with the potential for another foot of snow by Friday morning. 


Fitz will issue the next advisory tomorrow morning, March 29th.

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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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.


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