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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, February 10th 2014
Created: Feb 10th 6:45 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.
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.
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The Bottom Line

There is a MODERATE avalanche danger today at elevations above 2,000', these areas are just below treeline and above treeline. Human triggered soft slab avalanches 14-20" deep are possible on slopes 35 degrees and steeper. Most likely places to find and trigger a soft slab are slopes with recent wind loading or where the new snow from Friday is still a cohesive slab. The majority of Friday's snow is loose and unconsolidated.

Below 2,000' the danger is LOW. These lower elevations harbor 2-14" of loose snow over either ground or a crust and triggering an avalanche is unlikely.


Primary Concern

A bump in wind this morning will be the main player in the avalanche game today. There has been a change in the weather overnight and skies are cloudy with a chance for 1-2" of snow. The winds have just begun to increase from the East and are expected to reach the 25-30 mph range before decreasing this afternoon. Though this is a relatively small bump in wind with little new snow, we do have ample light snow available for transport - especially in the Turnagain Pass area. This is from Friday's localized snow storm that deposited up to 18" on Turnagain Pass.

The real concern, however, is how the wind may form slabs that can overload the weak faceted snow which sits underneath the recent storm snow. Friday's storm snow has become very loose due to Saturday and Sunday's clear and cold weather (see a couple more obsevations sent in yesterday HERE and HERE). This has decreased the slab properties that were present on Saturday and subsequently no new avalanche activity was seen on the Pass yesterday. Today's winds however could change that by forming new wind slabs. Any fresh slabs formed have the potential to be quite sensitive to human triggers as they will be be sitting on weak snow.

For anyone getting out today, keep an eye out for areas where Friday's snow is cohesive and especially where it is supportable to your weight. Watching for recent wind deposited snow, cracking or collapsing as well as quick hand pits are good ways to assess this.


Secondary Concern

At the upper most elevations, weak snow exists near the ground under the majority of the snowpack (4-6+' deep).  This is responsible for the deep slab problem. There is a low likelihood of triggering a deep slab in comparison to the shallow persistent slab.  However, the possibility lingers for triggering a slab that can pull out snow to the ground. Avoiding likely trigger points, especially areas where slabs are thinner, will lower the likelihood of triggering a deep slab avalanche. 

This problem is not a concern below 3000ft where the previously water saturated layers have now frozen into a very strong and stable crust layer.


Mountain Weather

Clear skies and ample sunshine greeted folks that were out yesterday. Winds were calm and though temperatures were in the 10F range, it felt quite warm. Valley bottoms remained cold and in the single digits. 

Overnight, clouds have moved in and a trace of snow has fallen with a possible 1-2 inches expected through the day. Winds have just starting to increase this morning and are forecast to be in the 25-30 mph range with stronger gusts from the East. Temperatures should increase as well to 20F at 1,000' and the low teens on the ridgetops. This change in weather is due to a low pressure center spinning in the Northern Gulf that is just strong enough to send a bit of moisture our way.

This system should exit this afternoon and a return to dry weather and mostly sunny skies are in store for Tuesday and Wednesday. For later in the week, we might start seeing more of a classic wintertime pattern with a low setting up over the Aleutians - which means possible snow in the forecast.

Sun effect?
Believe it or not the sun has been able to create a crust on southerly slopes. This was seen mainly in the mid and lower elevations (2,500' ish).

 

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 15, 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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