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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, March 5th, 2015 - 7:00AM
Expires
Fri, March 6th, 2015 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Much of the terrain in the Turnagain Pass area has a LOW avalanche danger where triggering an avalanche will be unlikely. However, there are areas in the Alpine zones (above 2,500′) that continue to have a MODERATE  danger and triggering a slab avalanche 1-2′ thick is not out of the question. These areas are most likely to be found in the “steeps” – steep rocky terrain with unsupported slopes as well as steep gullies and rollovers. Avoiding lingering wind slabs in these areas will also hedge your bets.

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Thu, March 5th, 2015
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. 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
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

As most of us know, the mountains around Turnagain Pass are in much need of a refresher (snow to the road is yet another story). However, there is winter up high and Tuesday night we received a welcome 2-3″ of moist snow above 2,500′, which has improved riding conditions. In the big picture, it has been almost three weeks since our last significant precipitation event and avalanche cycle with the last of our avalanche activity ending 10 days ago. Since then, we have been monitoring a buried layer of weak faceted snow, weak snow surrounding sun crusts on Southerly aspects and wind slabs. All of these snowpack concerns are in the top 2′ or so of the pack and continue to show reactivity in pits in some areas but not all. What all this boils down to is, we are still concerned that someone could trigger a slab avalanche in the steep, more extreme, terrain above 2,500′.

Things to keep in mind today if visibility allows for travel in steep terrain:

1)  Safe travel protocol – one person at a time on a slope, watch your partners, have an escape route planned if the snow moves.

2)  No signs of instability are likely to be present, but that doesn’t mean the snowpack on the slope you are hitting is stable or the wind drift is locked into place.

 

Photos below are of Tincan yesterday in low light where 2-3″ of new damp snow covered old tracks and provided some fun carvey riding conditions!

   

Weather
Thu, March 5th, 2015

Overcast skies, mild temperatures and calm winds greeted backcountry travelers yesterday. The clouds just started to part at the end of the day as the low-pressure system that put down a few inches of new snow Tuesday moved out.

We should see a break from our warm temperatures after today as a cold front slides through Southcentral later tonight. Until then, partly cloudy skies and valley fog will remain through the day with temperatures in the upper 20’sF on the ridgetops and the upper 30’sF at 1,000′. Ridgetop winds will be 5-10mph from the East with a flurry or two that could be squeezed out of the clouds.

Beginning tomorrow, cold air slides in from the Northwest associated with a large-scale trough currently over the Bering. You can see this in the IR satellite image  – the cold front is just passing through Western AK this morning – exciting news.  Along with the colder air will be the chance for snow to sea level. This flow direction is not ideal for Turnagain Pass as opposed to Hatcher Pass, who could see a bit of snow.  Stay tuned on how this pattern change will develop for the weekend! And, if you are headed North  this weekend remember to check out  Hatcher Pass’s Saturday AM advisory.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33   0   0   40  
Summit Lake (1400′) 34   0   0   7  
Alyeska Mid (1700′) 35   0   0   24  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26   E    5 18  
Seattle Ridge (2400′) 28   n/a    10 17  
Observations
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02/22/24 Turnagain Observation: Turnagain, Seattle, Mt Ascension
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02/20/24 Turnagain Observation: Seward Highway across from Johnson Pass TH
02/19/24 Turnagain Avalanche: Base of Seattle Ridge
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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.