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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, March 11th 2013
Created: Mar 11th 5:22 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.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The avalanche hazard is generally LOW in many areas today.  Exceptions are on and below steep upper elevation South/Southwesterly aspects where the threat of cornice fall and loose snow avalanches will increase the hazard to MODERATE as the day warms.


Primary Concern

While the likelihood of triggering a cornice today will vary from slope to slope, the consequences of being near or under a cornice as it releases will be high.  Cornices have grown very large over the last several series of storms.  We have seen what can happen when one of these backcountry bombs impacts a slope.  We also received a report of a large cornice fall over the weekend in the Goldpan area that pulled out snow to the ground (stay tuned for more info on this avalanche).  Most cornices in the Turnagain Pass area are found on South and Southwest aspects.  Pay attention to what's above you when traveling up valleys and what is below you while moving along ridgecrests.  Try to imagine what would happen if one of these beasts broke below your feet or sled or came hurtling down towards you and adjust where and how you travel accordingly.  The tricky part about potential cornice release is that it is hard to predict when they will release.  The chances of them releasing will get better as the sun hits those South and Southwest aspects. Planning your day by moving off of sunlit aspects as the surface becomes damp will allow you to minimize your expsoure to cornice falls as well as loose snow avalanches today.


Secondary Concern

As the day heats up on sunlit aspects, expect loose snow avalanches to become easier to trigger.  Combine these relatively small avalanches with isolated pockets of wind slabs and volume will increase to the point where snow could easily knock you over.  Getting knocked over above terrain features such as cliffbands, gullies and trees will make these avalanches harder to walk away from unscathed.  Loose snow sluffs will be dry on shaded northerly aspects and be more damp on southerly aspects.  As such expect sluffs to be moving faster on shaded aspects and have potentially higher volume on sunny slopes.

 

Additional Concern

Wind Slab
Yesterday my partner and I encountered fresh shallow wind slabs above treeline in the Girdwood Valley.  Average depth of new wind slabs are less than a foot where they exist.  Many areas did not recieve enough wind to create wind slabs.  However, there was enough variation in wind patterns over the weekend that isolated pockets exist.  Also be on the lookout for older pockets of wind slab that were created with the high winds of last week.  These will be less likely to trigger but are still out there, particularly in steep upper elevation starting zones.


Mountain Weather

In the past 24 hours the mountains around Turnagain Arm have picked up a few inches of new snow.  Winds have been generally light out of the East at 10 mph with gusts to 20 mph.  Temperatures have been in the upper teens at 3,880' with freezing level remaining around sea level.

This morning lingering snow showers should give way to clear skies by this afternoon.  Winds will average 10mph out of the North.  Temperatures at 1,000' will be in the low 30s F.

High pressure will dominate over the next several days with clear skies and relatively mild temps.

__________________________________________________________________

Wendy will issue the next advisory tomorrow morning, March 12th.

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be 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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
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