Friday, December 30th 2016 5:09 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
A CONSIDERABLE avalanche danger exists in the mountians surrounding Turnagain Pass on all slopes out of the trees. Strong winds are expected to form wind slabs that could release naturally and be easy to trigger by a person. Winds could blow below ridgelines and load, or cross-load, slopes that sit near treeline that are exposed to wind.
In sheltered areas a MODERATE danger exists where triggering a slab avalanche 1-2' thick, that breaks in older snow, remains possible. This was the case yesterday when a human triggered slab avalanche caught and carried three skiers (Please see details in the 'Persistent Slab' section below).
Johnson Pass region: A shallower snowpack exists in the mountains South of Turnagain Pass. We have no information in this area yet - if you are headed this way, a conservative mindset is recommended along with easing into terrain. Triggering a slab avalanche is possible and could be triggered from below, similar to what occurred to three skiers yesterday.
Safe travel protocol will be essential if you choose to enter avalanche terrain: Expose one person at a time, group up in safe zones, watch your partners and always have an escape route planned.
|Show the Complete North American Avalanche Danger Scale|
|Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.|
|Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.|
Johnson Pass North and South are open as of 7am this morning to motorized use. Please stay on the designated motorized trail - map HERE. The snowpack is unknown and questionable in this area - please read the following forecast.
*Alaska DOT may not get to clearing the Turnagain Pass motorized lot this weekend. Please park safely and respect plow operations.
A quick moving storm is impacting Southcentral currently. We have seen light snowfall overnight with an additional 1-3" expected today. The big news is however, the WIND... Westerly winds are slated to ramp up into the 30-45mph range with stronger gusts along the ridgelines.
Snowfall Totals so far:
Girdwood Valley: 3-5"
Turnagain Pass: 2-3"
Summit Lake: 3-4"
WIND SLAB AVALANCHES:
With plenty of older loose snow available for transport and a few new inches, fresh wind slab avalanches should be expected. These could release naturally, or be easily triggered by a person. They could be anywhere from a shallow 6" slab to a thicker, more concerning, 18" slab. This flow direction is known to load Easterly slopes on Seattle Ridge, such as Repeat Offender. On the East side of Turnagain Pass, this flow often loads Northerly slopes on ridgelines such as Tincan, Sunburst and Magnum.
*Keep in mind that newly wind loaded slopes could overload buried weak layers and a wind slab avalanche could 'step-down', triggering a larger slab avalanche.
We are glad to report a positive outcome to a near miss avalanche yesterday on the Lipps ridge. Three skiers were caught and carried in a slab avalanche while they were ascending the common up-track on the lower portion of Lipps. The avalanche was triggered in a thin area and propagated above them. The slab washed over all three and they were carried 1-200' (estimate) before they all ended up on the surface of the debris. Forecasters will investigate this avalanche today and a more detailed report, with the events shared by the party members along with avalanche details, will be finalized soon. You can see more photos in the preliminary report HERE.
PERSISTENT SLAB AVALANCHES:
The Lipps slide was believed to be a persistent slab that broke in weak faceted snow 1-2' below the surface. This set up exists South of Turnagain Pass (including Johnson Pass and Lynx drainages). There is a variety of weak layers that sit 1-3' below the surface and triggering a slab breaking in the old snow remains possible. Pay attention to:
- Whumpfing / collapsing
- Cracking in the snow
- Hard stiff snow over softer old sugar snow
- Thin areas of the slab - these are likely trigger points
- These avalanches can occur when no signs are present as well - more reasons to follow safe travel protocols.
Photo from the Lipps avalanche yesterday taken by a member of the group involved. We thank these folks for their willingness to share.
Mostly overcast skies covered the region yesterday. Ridgetop winds were light from the North and East and no precipitation fell. Temperatures rose dramatically from single digits at 7am to 20F by 7pm (in response to a warm air mass moving through from the West).
Overnight, we have seen light snowfall in Girdwood, Turnagain Pass and Summit Lake as a warm storm system impacts Southcentral. This system looks to be favoring the Girdwood and Western Kenai Mountains, including Summit Lake, snowfall totals mentioned above and in chart below. Another 1-3" of snowfall is forecast for today before skies begin to break up. STRONG Westerly ridgetop winds (30-45mph) are expected during today bringing cold air - it should be chilly and blizzard like on the ridgelines!
Tomorrow, the cold single digit air mass will remain over us with clear skies and no precipitation expected.
PRECIPITATION 24-hour data (6am - 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880')||19||2||0.2||39|
|Summit Lake (1400')||17||3||0.3||12|
|Alyeska Mid (1700')||20||3||0.3||29|
RIDGETOP 24-hour data (6am - 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Sunburst (3812')||Under Repair||Under Repair||Under Repair||Under Repair|
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).
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: May 06, 2018 )
|AREA||STATUS||WEATHER AND RIDING CONDITIONS|
|Johnson Pass:||Closed||Closed as of April 20th|
|Placer River:||Closed||Closed as of April 17th|
|Skookum Drainage:||Closed||Closed as of April 1st.|
|Turnagain Pass:||Closed||Closed as of May 7th. Happy summer, see ya when the snow flies!|
|Twentymile:||Closed||Closed as of April 13th|
|Carter Lake:||Closed||Closed as of 4/27|
|Lost Lake Trail:||Closed||Closed as of April 13th|
|Primrose Trail:||Closed||Closed as of April 13th|
|Resurrection Pass Trail:||Closed||Closed as of April 20th|
|Snug Harbor:||Closed||Closed as of 4/27|
|South Fork Snow River Corridor:||Closed||Closed as of April 13th|
|Summit Lake:||Closed||Closed as of April 20th|
SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email email@example.com
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.