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Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, March 14th, 2017 - 7:00AM
Expires
Wed, March 15th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

A  LOW  avalanche danger remains in the backcountry  at all elevations. Although triggering an avalanche is unlikely, it is not impossible on steep wind loaded features and in extreme terrain.  Be aware of old hard wind slabs and loose dry avalanches(sluffs) in steep terrain, as well as large cornices. Glide cracks continue to open – limiting exposure under these is recommended.

Good travel habits are important, even during ‘green light conditions’. These include exposing only one person at a time on a slope, watching your partners closely and having an escape route planned in case the snow moves.  

Summit Lake, South of Johnson Pass and North in parts of the Girdwood Valley (around Crow Pass):  A reminder that the snowpack remains thinner in these areas with a poor structure. There is still a chance for triggering an avalanche deeper in the snowpack in these areas. Read the  Saturday Summit Summary  HERE.

 

Tue, March 14th, 2017
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

The weather DJ seems to have left the buliding and the weather pattern continues to be stuck on repeat. Sunshine, sunshine, sunshine… Yesterday cloudy skies in the middle of the day were almost a tease. Today there will be an uptick in afternoon NW winds to add a little spice but really the story remains the same. We have seen 20 days without any precipitation and nine days since a wind event impacted our region. Despite the weather and snowpack conditions being mostly stable and the weak layers dormant, a hard wind slab 12-18” deep was triggered by a snowmachiner three days ago on a SE aspect of Seattle Ridge. This is a good example of a wind loaded terrain feature still harboring unstable snow and a good reminder that LOW danger does not mean NO danger. Kicking off even a small wind slab or loose snow avalanche in steep terrain may have high consequences. Things to keep in mind if you are headed to the mountains today:

Wind SlabsOld and hard winds slabs are easy to find but for the most part they are locked into place. Smooth pillowed snow on steep unsupported features or in rocky areas will be the most suspect zones for someone to initiate an old wind slab. Pay attention to blowing snow today if the NW winds start to pick up any soft snow. There is not much left to transport. Watch for shooting cracks if slopes are actively being loaded.

Loose Snow Avalanches (Sluffs): Dry sluffs on steep slopes are probable and have been fast moving this week.

Glide Avalanches: Glide cracks continue to slowly open above popular terrain on Seattle Ridge and in other areas of the advisory area. These could release at any time, watch for these cracks and avoid being under them.

CornicesCornices should always be given a wide berth from above and limit exposure time traveling underneath.

Persistent Slabs and Deep SlabsThere are various weak layers in our thin snowpack. Buried surface hoar sits 1-3+’ below the surface and faceted snow sits in the mid and base of the pack. These weak layers with varying degrees of strength are in a dormant stage due to plenty of time to adjust with a lack of changing weather. Although its unlikely, an avalanche breaking deeper in the pack isn’t completely out of the question in Johnson Pass, Lynx Creek and in parts of Girdwood Valley (especially around Crow Pass). 

This hard wind slab was initiated by a snowmachine just below the trees, lookers left side of photo, while exiting the slide path. This was on a SE aspect of Seattle Ridge at 2400′ in an area near ‘God’s Country’. Photo by Brian Bird.

 High clouds over Seattle Ridge yesterday. Note the series of glide cracks along the ridge that continue to open.

Weather
Tue, March 14th, 2017

Yesterday high clouds rolled into the region as a short wave passed over. Skies cleared in the evening. Winds were light and variable. Temperatures were in the teens to low 20Fs. Overnight the temperatures dropped into the single digits.  

Today is forecasted to be clear, sunny and cold. Valley temperatures may hit the low 20s but the ridge tops will remain in the single digits to low teens. NW winds are expected to pick up with gusts into the 20s. Tonight temperatures may drop below 0F.  

Tomorrow will be partly to mostly cloudy with a chance of light snow in the afternoon and the colder temperatures will continue. There is hope that the overall pattern will change more significantly early next week.  

*Seattle Weather Station tables and graphs are not recording temperature history.  The current temperature at 7 am was 7F.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 11   0   0   59  
Summit Lake (1400′) 8   0   0   28  
Alyeska Mid (1700′) 14 0 0   56  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  8 variable    3  9
Seattle Ridge (2400′)  *n/a variable    4    12
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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.