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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Sunday, April 3rd 2016
Created: Apr 3rd 6:34 am
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Silverton Mountain Guides
Special Announcement

CNFAIC is going to Arctic Man for the fifth year in a row! We are excited be there all week and to offer two FREE companion rescue workshops. Click HERE for more information. We hope to see you there! Stop by the blue trailer and practice in the beacon park! Don't forget your beacon, shovel and probe!


The Bottom Line

The avalanche danger is CONSIDERABLE below 3000’ due to an increase in frequency of large destructive glide avalanches. There are several areas where glide cracks threaten popular terrain and travel in these zones is discouraged. Today warm temperatures and sun will increase the likelihood for human triggered wet avalanches below 2500’ adding to the danger in the Treeline zone. Cautious route-finding and careful terrain evaluation are essential to avoid being under the runout of glide cracks.

In the Alpine, where a stout surface crust has formed, the avalanche danger is LOW. Remember it is springtime and if the sun melts this crust, wet loose activity is possible later in the day.

*Summer use trails with avalanche terrain above should be avoided due to serious threat of natural avalanche activity from above. Byron trail in Portage Valley is not a recommended and the Turnagain Arm Trail between Bird and Girdwood, remains CLOSED, due to dangerous avalanche conditions.

*If you are headed to the Summit Lake area don't forget to check Summit Lake Summary


Primary Concern

Glide avalanches are unlike any other avalanche problem and don’t fit well in the North American Danger Scale. They release without warning and are not associated with human triggers. They are a high-risk low likelihood avalanche problem, and the only way to mange this problem is by avoiding terrain with glide cracks.

SO WHAT DOES THIS ALL MEAN?

We as avalanche forecasters have NO IDEA which glide cracks are going to release on any given day. What we do know is the frequency of glide avalanches is on the rise. Since Friday (4/1) five large glide avalanches occurred on Seattle Ridge, including one mid-day yesterday. Another handful of glide avalanches were also observed yesterday between Girdwood and Turnagain Pass.

The reason this is so alarming is that new glide cracks are appearing daily and many threaten popular terrain. The Seattle Ridge uptrack is one of our biggest concerns because a large crack now puts this popular route in the line of fire. If you were to be in the wrong place at the wrong time you would not survive a glide avalanche. High marking or setting a skin track under a glide crack is not recommended EVER!

 

Recent high marking was observed yesterday below a large glide crack on Seattle Ridge. Notice how portions of the uptrack are also within the runout of this fast growing glide. 

 

 

We were impressed by the frequency and size of the glide activity on Seattle Ridge yesterday compared to the day before.

 

A glide avalanche occured mid day yesterday on Seattle Ridge accross from the Sunburst parking lot.

 


Secondary Concern

As we work our way through this springtime regime and transition from a winter snowpack to a summer one, it's time to think about how the surface is warming/softening, or not warming/softening. This is not only for sussing out good ski/riding conditions but for wet avalanche hazards as well. Yesterday we saw unsupportable and wet snow below 2,500' where it was easy to initiate wet sluffs in steep terrain. Has this wet snow frozen overnight? Most likely there has been a shallow re-freeze limiting any wet avalanche hazard. However, temperatures climbing today and the likelihood of sunshine may soften surface crusts again, allowing for wet avalanche activity to increase throughout the day. Mid elevations below 2500’ will be the most suspect, but you should still pay attention to solar aspects in the Alpine.

Wet snow rule of thumb: If the snow is wet and mushy enough for your boot to sink in up to your ankle, or more, wet sluffs are possible and it's time to find a more supportable slope. Also, wet sluffs can be quite dangerous as the debris is heavy, can generate a lot of momentum and be extremely difficult to escape.

 This a great way to test the strength of the snow. If the snow is unsupportable and you are punching through avoid steep terrain. 


Additional Concern

We have yet to start seeing cornices begin to fall in earnest, yet it is still wise to give these very large snow features a wide berth along ridgelines and limit your time below them. Cornices typically calve off around now as we move into a springtime snowpack.


Mountain Weather

 

Yesterday skies were mostly cloudy and scattered showers left a trace of new snow in the Alpine. Daytime temps reached a high of 42F at Center Ridge SNOTEL and overnight temps reached a low of 28F. In the alpine temperature remained cooler, mid to high 20F’s and ridgetop winds were Light to Moderate from the East.

Today will be mostly sunny and temperatures will likely reach the mid 40F’s at 1000’.  In the alpine temperatures are expected to reach the mid 30F’s and Ridgetop winds be light, 5-10mph, from the East. Overnight temps are expected to drop into the 20F’s.

Tomorrow looks like more cloud cover with a chance of scattered rain/snow showers and patches of sun. Similar temps and winds are expected tomorrow.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 35  trace  0.1  118 
Summit Lake (1400') 35  37 
Alyeska Mid (1700') 35  trace  0.01   105

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  NE  23 
Seattle Ridge(2400') 27  SE  14  31 

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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