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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, December 28th 2014
Created: Dec 28th 5:39 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'
 Show the Complete North American Avalanche Danger Scale
BP Alaska
The Bottom Line

A MODERATE avalanche danger continues on all aspects above 2,500'. The potential remains for triggering a 2-3' deep slab avalanche on slopes over 35 degrees. This includes slopes that have already been traveled. There were two skier triggered avalanches yesterday in the Girdwood Valley - see details on those below. Fresh wind slab avalanches 6-10" thick will also be possible to trigger due to strong winds moving in currently ahead of a multi-day storm.

At the treeline elevations (1,000'-2,500') there is a LOW danger where it will be unlikely to trigger an avalanche. However, keep in mind what is above you. If an avalanche is triggered from a party above, could it wash into your location?

Early season hazards (rocks, stumps, alders) continue to be a challenge below 1,500' with the minimal snow cover.


Primary Concern

A beautiful day yesterday saw many folks out enjoying the backcountry. Slowly but surely people are testing the steeper slope angles - but not the real steeps, yet. This is due to an 11-day old and stubborn layer of buried surface hoar 2-3' deep in the snowpack.

In the Girdwood Valley, however, things were a bit different yesterday where two skier triggered avalanches occurred. This was in the Raggedtop zone and, interestingly enough, in the same spot. No one was caught, luckily. You can read the account HERE and watch the video. The second avalanche took out the entire first avalanche as the fourth person in the group skied down a very similar line to the first three. The weak layer is suspected to be facets near the ground. Although this is a different weak layer than the buried surface hoar at Turnagain Pass, it is still a "persistent weak layer" that sits under a slab and the same caution applies.

Photo below: The second avalanche triggered on Raggedtop by the fourth skier down the slope - seen on the right. (East facing ~4,000')

 

For today, forecasted cloud cover and strong winds may deter travel in the upper alpine, but if you do decide to get into bigger and steeper terrain, it will be crucial to manage yourself and your group appropriately: 

Avoid trigger points, such as steep rollovers, rocky zones and areas where the snowpack is thin
Only expose one person at a time
Utilize islands of safety
Have an escape route planned, and communicate plans and decisions effectively


It is getting to the point where the buried surface hoar is harder and harder to trigger in our test pits and time is on our side. Chances are steep upper elevation slopes can be ridden without incident, but there is still a chance you could pull out a slab too.  Slabs have the potential to propagate across slopes and carry enough volume and speed to injure and bury a person.


Secondary Concern

Both old and fresh winds slabs will be something to watch for in areas above treeline. Old wind slabs 8-12+" thick, that formed during Christmas Day's strong Southerly winds, may still be touchy where they are sitting on weak faceted snow (Summit Lake area or Girdwood Valley).

Today the winds are forecast to become strong from the East - averages in the 30-40mph range - by the afternoon. In this case, watch for new wind slabs forming on leeward slopes. There is not a lot of loose surface snow available for the winds to transport, but enough I suspect to form 4-10" slabs in some areas. Additionally, the wind direction is East as opposed to South, as in the Christmas event, that will possibly provide the wind additional loose snow to work with.

Watch for plumes off peaks today and steer clear of slopes seeing current wind loading. Areas below 2,500' will not only have less wind effect and lower avalanche danger, but will harbor the better riding conditions as well.


Mountain Weather

Yesterday was the calm before the storm. A few high clouds filled the skies in the afternoon while the winds were calm to light and variable on the ridgetops. Temperatures were mild, in the mid 20'sF at 3,000'.

Today, we will see the first part of a large storm system move in that is currently impacting areas to our West. A series of low pressure centers following a warm southerly flow will bring strong ridgetop winds to our neighborhood. Winds are forecast to average in the 30-40mph range from the East. Precipitation is not likely to start until tonight when 2-3" of snow is forecast at 1,000' and possibly snow all the way to sea level. Temperatures should remain in the mid 20's on the ridgetops and near freezing at 1,000'. 

Monday and Tuesday, the warm, wet and windy southerly flow will continue. We are on the dry side of the mountains to some degree and models now are showing 3-5" of snow for both Monday and Tuesday. If the models are right, by Wednesday we could have around a foot of new snow. The rain/snow line looks to hover right around 1000-1500', but this line could change fast.

A high pressure looks to build later in the week bringing clear skies. Stay tuned.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29   0   0  29 
Summit Lake (1400') 18  0 0
Alyeska Mid (1700') 28   0  23.5 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  29 
Seattle Ridge(2400') 24  SE  11  36 

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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