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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, March 29th 2017
Created: Mar 29th 4:12 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
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The Bottom Line

The avalanche danger is HIGH on all aspects and elevations today. 1-2' of new snow sits on weak snow. Both natural and human triggered loose snow and slab avalanches are likely.  More snow fell in Portage, Placer and Girdwood Valley than on Turnagain Pass, avalanches will be larger in those areas. Travel in avalanche terrain is not recommended.

Keep in mind the additional springtime possibility of the sun shining during a pocket of afternoon clearing and natural avalanches on Southerly slopes. 

Hiking in Portage Valley: Travel past the end of the designated Byron Glacier trail in not recommended due to exposure to avalanche terrain. Natural avalanches are likely today.

Summit Lake: Read the Saturday Summit Summary HERE.


Primary Concern

An active weather pattern has finally returned to Southcentral. Yesterday saw periods of heavy snow, rain showers up to 1100' and gusty winds along ridge tops. There was also an afternoon spike in temperature bringing the warmest we have seen this spring. Snow continues to fall this morning bumping storm totals to over foot across the region and up to 2' in Girdwood Valley, Portage and most likely Placer. Spring storms can bring somewhat complicated avalanche conditions to mountains due to the variety of issues. Today due to active loading and the chance of clearing in the afternoon with direct sunshine we recommend avoiding travel in avalanche terrain. Avalanches may run into the flats below. Avoid runout zones. 

STORM/WIND SLABS: Snow surface prior to this storm consisted of surface hoar with loose faceted snow underneath on shaded aspects, and a sun crust on solar aspects (SW - SE). Both of these surfaces will be hard for the new snow to stick to. Storm related slabs are likely and are expected to be easy to initiate. Easterly ridgetop winds yesterday will have also made slabs more cohesive on leeward slopes. These could be hard to distinguish due to new snow on top. 

DRY LOOSE SNOW AVALANCHES (SLUFFS): Both natural and human triggered dry loose snow avalanches on steeper terrain are likely especially on slopes with slick sun crusts and features protected from any wind. 

WET LOOSE AVALANCHES: If snow turns to rain wet loose activity will be likely at low elevations. In addition, if there is afternoon clearing and the sun pokes out warming the snow surface, wet loose avalanche activity on Southerly slopes will also be likely.

Tincan yesterday. Photo: Andy Moderow

Petes South at 6:00 pm. Recent loose snow avalanches on the south face after a period of clearing. 

 


Additional Concern

Over the weekend there were two human triggered avalanches. On Saturday there was a snowboard triggered slide in Warm-up Bowl on a slope with previous tracks on it. On Sunday there was a small slab avalanche on a steep Northern chute on Orca, near Girdwood. These are good reminder that some slopes harboring old slabs 1-2' thick are sitting on weak faceted snow. These slabs are composed of last week's storm snow. There is a chance that avalanches occurring today could step down to weak layers deeper in the snowpack, another reason to avoid avalanche terrain today. 

 

 

Warm-up Bowl snowboard triggered avalanche. Photo: Craig Brokensha


Mountain Weather

Yesterday was an active weather day with periods of heavy snow, rain showers below approximately 1100', pockets of clearing, gusty SE winds and rapidly warming mid-day temperatures. Accumulations ranged from around 6" at Turnagain Pass to over a foot in Girdwood, Portage and Placer. Temperatures spiked in the late afternoon with Center Ridge hitting 39F around 1 pm. Precipitation turned from rain to snow at lower elevations for a few hours. SE Winds were 10-20 mph and gusted into the 30s. 

Overnight temperatures dropped into the 20s and snowfall picked up early this morning adding to the snow totals. Snow is expected to continue today with an additional 3-11" forecasted. Winds will be light and easterly. Temperatures will be in the 20Fs to low 30Fs. There will be a break in systems this evening with the next storm moving in tomorrow afternoon. This next storm is forecasted to be stronger and warmer. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  6 .4  69
Summit Lake (1400') 29 7 .4 36
Alyeska Mid (1700') 30 13 .9 72

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 21   ENE  12 37 
Seattle Ridge(2400') 24  SE  12 30 

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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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