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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, March 24th 2016
Created: Mar 24th 5:57 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.
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'
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The Bottom Line

The avalanche danger is CONSIDERABLE at Treeline (below 2500’) in Turnagain Pass where glide avalanche activity has been especially active in the last two days. Due to a wet and saturated snowpack human triggered wet loose avalanches in steep terrain (greater than 35 degrees) are also possible in the mid elevation zone and will be more likely in the afternoon with the influence of solar heating. Cautious route-finding and terrain evaluation are essential today to avoid being under the runout of glide cracks.

In the Alpine above 2500’ the avalanche danger is MODERATE, where triggering a cornice, wind slab or wet loose avalanche are possible and will increase with daytime temperatures. 

*If you are headed to the Summit Lake area don't forget to check Summit Lake Summary here and an HERE for observation from yesterday.


Primary Concern

We have been talking about glide cracks and glide avalanches for months and the past couple weeks have been notably active. In the past couple days our concern for glide avalanches has become more elevated with a wet saturated snowpack and four nights of above freezing temperatures. New cracks are appearing and releasing, and old large cracks are also releasing without warning. The entire East face of Seattle Ridge is covered including the area of Repeat Offender, which has seen accelerated movement in the last two days. The area near the ‘uptrack’ is getting more cramped, with little wiggle room for safely playing in this area. The idea of parking under or someone getting a machine stuck under a glide crack is a total dice roll. Navigating through the mid-elevation band is getting more and more complex. The only way to mange this hazard is avoidance. 

Yesterday glide activity on Seattle Ridge was impressive and several small lobes released near the uptrack. Click HERE for an observation of glide activity from Yesterday.

 

 

Many new glide avalanches were observed yesterday in Girdwood, Twentymile, and Turnagain Pass, including this one on the SW shoulder of Pete's South. 

 

Uptrack is on far right side of picture; glide cracks cover and have almost connected the entire lookers left side of Repeat Offender on Seattle Ridge

 


Secondary Concern

Yesterday temperatures reached the 50F’s at sea level, and for the fourth night in a row the mid elevation zone remained above freezing. This is not helping our wet and saturated snowpack stabilize very quickly. Wet loose natural activity was observed yesterday on all aspects, and on solar aspects the activity was larger and more notable.

Today triggering a wet loose avalanche will be possible below 2500’ on slopes steeper than 35 degrees. Wet avalanches once initiated can entrain more snow rapidly and are very hard to get out of. They can be particularly hazardous if they push you into a terrain trap and bury you deeply. If your skis or snowmachine are sinking deep into wet snow this is an obvious clue that the snow is unstable. Stick to low angle terrain and avoid runout zones where avalanches from above may catch you. Today’s weather forecast is for scattered rain showers, which could mean periods of sun. If the sun becomes more of a theme than cloud cover, expect natural wet avalanche in the alpine on solar aspects as well.

Wet loose activity observed yesterday morning on the West face of Magnum before the sun and day time temperatures started playing a roll.

 


Additional Concern

Wind slabs and Cornices:

Finding a lingering wind slab 1-2’ thick is possible in steeper terrain today and will be more likely to trigger during the heat of the day on solar aspects. Watch for cracking in wind-loaded areas and avoid travel on or under cornices. Today’s warm temperatures will make cornices more likely to fail. 


Mountain Weather

Yesterday daytime temperatures reached a high of 48F at the Center Ridge weather station and a high of 51F at Bird Flats. Ridgetop winds were calm and skies were mostly sunny throughout the day.

Overnight temperatures barely reached freezing (31F) at Seattle Ridge weather station as of 6am. At Center Ridge weather station there was an overnight low of 37F, which has an elevation of 1800’. Ridgetop winds were light from the Northeast and no precipitation was recorded in the last 24 hours.

Mid elevation temperatures will likely reach the mid to high 40F’s and temperatures in the alpine will also be above freezing for most the day. Scattered rain showers will move through the area, but only a trace of precipitation expected. Expect Northeast ridgetop winds to be in the 10-20mph range.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 40  127 
Summit Lake (1400') 38  42 
Alyeska Mid (1700')  38 106 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 32  NE  15 
Seattle Ridge(2400') 35  SE  12 

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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