Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 4th 2017 7:00 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

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. 

 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement
  • 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.

Avalanche Problem 1

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

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. 


Mountain Weather

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 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 27 
Seattle Ridge(2400')  38  NNW  4  13

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.

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