Turnagain Pass RSS

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, December 17th, 2016 - 7:00AM
Expires
Sun, December 18th, 2016 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a HEIGHTENED  MODERATE avalanche danger at all elevations in the mountains around Turnagain Pass. Very sensitive wind slabs have formed over the past 24 hours due to 3-7″ of new snow and moderate winds. These slabs are shallow, around 4-10″ thick due to the low snow amounts, but are expected to be easy to trigger. With limited snowfall data, watch for thicker, more concerning winds slabs in areas receiving more snow/wind.

It will be very important to monitor how much new snow has fallen in the area you are traveling. This will determine how thick wind slabs will be.  

AVALANCHE DANGER is expected to rise tomorrow as a powerful storm moves through.

*Ice climbers and hikers: The potential exists today, and more so tomorrow, for debris to run through gullies into terrain below 1000′ in the Portage Valley; due to an avalanche occurring above. More snow and wind exists in Portage than other areas.  

Special Announcements

What are you doing Tuesday night?? Come to the  Blue & Gold Boardshop for a CNFAIC presentation on the ‘Turnagain Pass snowpack’!! This will be an interesting discussion considering the interesting snowpack! Details on link.

Motorized use:  The Chugach National Forest is monitoring snow coverage across the Forest daily for a motorized opening. A 36 € base is a general number the Forest uses to determine adequate coverage – this could be more or less depending on snowpack density. Thanks for your patience and don’t let up your snow dance €¦.. The forecast looks promising!  With an opening on the horizon, have you got your rescue gear out, practiced?? Check out this successful rescue a couple days ago in Colorado.

For Hatcher Pass avalanche conditions see their Saturday advisory  HERE.

Sat, December 17th, 2016
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Dangerous avalanche conditions. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

We have had very little snow so far in our upcoming week of stormy weather, but the snowpack is already showing its cards. Two shallow wind slabs were triggered yesterday by skiers/riders on Tincan and Eddies. These slabs were only 4-6″ thick, but are so touchy because they are sitting on VERY weak faceted snow. With another 2″ of new snow overnight and continued winds, we can expect today’s wind slabs to be a bit thicker – and just as touchy. 

What to watch for today:

    • Look for areas where the winds have deposited snow
    • Watch for cracks in the snow that shoot out from your feet
    • Although slabs are thin and avalanches expected to be ‘low volume’ they can still pose a problem if you get knocked off your feet and sent into a terrain trap

Remember safe travel protocol: expose one person at a time, have an escape route planned, group up in safe zones and be aware of groups around you.

Photo below from Adam Rothman showing the shallow wind slab on Tincan. This is a classic slope for wind slab avalanches. Keep in mind, it has likely reloaded and could be ready for another release.

So what about this snowpack???  

“This is a great layer for making avalanches.” Quote from Jim Kennedy, former Alyeska Snow Safety Director and current Alaska DOT Avalanche Program Director. 

What Jim is talking about is the snow surface from our two-week cold and dry spell, shown in the video below. Faceted snow is notorious for causing avalanches once it is buried – this is the EXACT set-up we have now. With only 3-7″ of new snow causing low volume avalanches now, this is a pre-cursor to what is to come with additional snow in the forecast for tomorrow.

 

Weather
Sat, December 17th, 2016

Yesterday saw mostly cloudy skies with a few snow flurries. Ridgetop winds bumped up and averaged in the 20-25mph range with gusts to 51mph from a Southerly direction. Temperatures warmed to 36F at sea level (ugh….), to the upper 20’s at 1,000′ and low 20’sF on the ridgetops.

Overnight around 2″ of moist snow fell above 300′ with light rain/drizzle falling at sea level. The rain/snow line looks to be around 200-300′. Snow amounts overnight for Portage Valley and the higher elevations could be in the 4-6″ range.  Today we should see cloudy skies and intermittent snow showers. Snowfall amounts during the day are expected to be anywhere from 0-2 inches. Ridgetop winds will be 5-10mph from a Southerly direction. Temperatures are expected to remain warm with a rain/snow line right around sea level.

The BIG news is how tomorrow’s storm is going to shape up. We are expecting winds in the 50-60mph range and snowfall in the 6″ to 1 foot range. Stay tuned on tomorrow’s advisory!!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   2   0.2   23  
Summit Lake (1400′) 29   0   0   9  
Alyeska Mid (1700′) 29   2   0.25   14  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 22   21   NE   51  
Seattle Ridge (2400′) 23    22 SE   48  
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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.
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