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Wed, January 4th, 2017 - 7:00AM
Thu, January 5th, 2017 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

A  MODERATE  avalanche danger remains in the Alpine where triggering an isolated wind slab or a deeper slab 2+’ thick is possible on steep wind loaded slopes that haven’t avalanched. At Treeline and below there is  LOW  avalanche danger, where triggering an avalanche is unlikely, but not impossible.

In the periphery zones of Girdwood, Johnson Pass and Summit Lake a much shallower snowpack exists and it may be easier to trigger a slab avalanche in these areas.   Check out the Summit Lake Summary  HERE  and click  HERE  for a recent observation from Max’s Mountain in Girdwood.  

Special Announcements
  • There is a Kenai Peninsula Avalanche Information Workshop this Sunday, January 8th at 5:30 pm at the Flats Bistro. Hope to see you there! More info HERE.

  • If heading to Hatcher this week – unstable conditions exist – check the Hatcher Pass advisory  HERE!    Mark your calendars for the FREE rescue workshop at Hatcher Pass on January 14th. More info  HERE.

  • For Turnagain Pass December Weather History Chart click  HERE.
Wed, January 4th, 2017
Above 2,500'
2 - Moderate
Avalanche risk
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
  • 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

Why you should still be concerned about PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW): Variable snowpack depth, hard slabs, persistent weak layers, and slopes that haven’t slid. The likelihood of triggering an avalanche is decreasing but depending on the specific slope the consequences could still be high. Things to remember today…

1) Its been 5 days since a big wind event loaded Northern aspects and cross loaded many Eastern aspects. This wind event as well as the Christmas snow storm caused widespread avalanching in the area. Avalanches were 1-3′ deep and large enough to kill or injure a person. Slopes that did not slide in either event should be approached with caution. Always consider how large a slope is and what other terrain it is connected to. Triggering a slab from below is still possible, especially on a snowmachine.

2) Several persistent weak layers are buried within the snowpack (facets and buried surface hoar), but strong supportable snow over top is making it stubborn to trigger.  The snowpack depths across the advisory region are variable. In the areas where a thinner snowpack exists several observers have experienced collapsing/whumpfing in recent days. Including an observer who felt/heard a loud collapse followed by a fast moving shooting crack on their second ascent up Max’s Mountain on SundayIt may be easier to find unstable snow in these areas. The tricky part is that obvious signs like cracking and ‘whumpfing’ are becoming less common in the Turnagain Pass area and may not be an early warning sign that a slope is still dangerous. 

3) Look for hard snow over soft snow – slabs can be strong enough to support the weight of a snowmachine or skier, allowing you onto them before they release. It could also be the 1st or 5th or 12th person or machine on the slope that tips the balance. Slabs on unsupported slopes in steep rocky terrain are prime suspects. Thin spots in the slab are likely trigger points. Always practice safe travel techniques in avalanche terrain.

  • Expose one person at a time
  • Watch your partners
  • Have an escape route planned
  • Watch for other groups
  • Consider, what will happen if the slope slides? 

Wind slab that propagated in a snow pit yesterday on Eddies on a Northerly wind loaded aspect. 

Avalanche on Magnum from the 12.30.16 wind event. Example of slide with high consequences and adjacent slopes that may still harbor a dangerous snowpack. 

Avalanche Problem 2
  • Announcement

The warm, above freezing temperatures at the ridge tops for over 36 hours is unusual. The snowpack has been settling steadily due to the temperatures and the Tincan Snow Profile Monitoring is showing that the snow near the surface is gradually warming. However, radiation is minimal at this time of year, no melting has been observed and clear nights with low humidity have allowed for radiant cooling. What does this mean for you traveling today? Probably not much but there is a chance that the settlement and warming have affected the slab character and could make triggering a little easier. 


Wed, January 4th, 2017

Yesterday was mostly clear in the morning with high clouds moving in during the afternoon. The inversion was in place again with valley fog and temperatures remaining above freezing in the alpine. Seattle Ridge again measured 40 degrees F a couple of times throughout the last 24 hours and has been recording above freezing since Sunday. Temperatures in the valleys were in the single digits to low teens. Winds were light and westerly.  

Today some high clouds may still be around but skies should be mostly clear. As the day progresses cooler air should filter in and help break up the inversion. Temperatures should be in the 30s at ridge tops and in the teens in the valleys.  Winds should start out light and westerly but get stronger throughout the day and shift to the NW.  

Tonight and tommorrow colder temperatures, clear skies and strong NW winds are on tap as a series of cold short waves from the Arctic move over the region. Winds are forecasted to really increase through the day tomorrow into the evening and continue through Friday. Temperatures should drop into the teens and low 20Fs. The pesky blocking ridge is still the main influence on the weather until sometime early next week. Expect much of the same weather throughout the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  33  0 0   36  
Summit Lake (1400′)  14  0  0  11
Alyeska Mid (1700′)  28  0  0  24

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 37    WNW 6   27  
Seattle Ridge (2400′)  38  NNW  4  13
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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.