Monday, February 24th 2014 6:28 am by John Fitzgerald
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
The avalanche hazard is MODERATE today above and below treeline. It will be possible for snowmachiners, skiers and snowboarders to trigger wind slabs 1-3’ in depth that formed yesterday on a variety of aspects and elevations. A layer of weak snow deeper in the snowpack also has the potential to release slabs anywhere from 2-4’ in depth in steep terrain.
Avoiding wind loaded features and steep terrain are your best bets for staying out of trouble today.
|Show the Complete North American Avalanche Danger Scale|
|Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.|
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Strong and gusty winds created very sensitive wind slabs during the day yesterday (see video & observation HERE). An ample amount of light density snow was moved easily by these winds and formed slabs 2-3 feet thick. We received one report of a snowmachine triggered avalanche in one of these wind loaded areas yesterday. details HERE. Natural and human triggered avalanche activity was observed and reported by multiple parties over the weekend.
Snowmachine triggered avalanche in a wind loaded starting zone in Triangle Bowl. No one was injured or buried. (Photo: Kolin Smith)
Today expect the sensitivity of these slabs to be on the decline. It will still be possible to trigger slabs in many areas, as the winds affected slopes above and below treeline yesterday. It’s important to learn how to recognize wind slabs. Gullies that have been cross loaded, cornices and wind lips at the top of slopes, and any snow that has a smooth, rounded or pillowy look to it are worth avoiding today.
Weak faceted snow that is sitting between the late January crust and the snow that has fallen in February continues to hold the potential for deeper slabs to release. This layer has been slowly gaining strength but still warrants your attention. Combine this problem in areas where newly formed wind slabs are up to 3 feet on their own and the consequences (volume and depth of debris) are potentially unsurvivable.
Choosing lower angled terrain, <35 degrees, is the simplest way to avoid triggering slabs up to 3’ in depth. Avoiding spots where slab depth quickly changes from thin to thick (i.e. starting zones, cross loaded gullies) will also help in avoiding trouble today.
The most significant weather factor contributing to instability over the last 24 hours was wind. Wind data from ridgetop stations were the following:
Sunburst- 13 avg - 55 gust out of the East
Seattle- 22 avg - 53 gust out of the South
Fresno- 18 avg - 40 gust out of the North
Temperatures over the last 24 hours averaged 17 degrees F at the Sunburst weather station. It has been 6 days since the last precipitation has fallen.
Today expect sunny skies. Winds speeds will remain elevated, averaging in the 20-30mph range out of the Southeast. Temperatures at 1,000’ will be in the high 20s to low 30s F
A ridge of high pressure over most of Alaska is preventing moisture from reaching our area. There is a slight chance for some light precipitation tomorrow, but much of that depends on the ability of that high pressure ridge to prevent low pressure from the south and west to move over us. The rest of the week looks to be dry and clear with slightly warming temperatures as high pressure will continue to dominate.
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: Jan 13, 2019 )
|AREA||STATUS||WEATHER AND RIDING CONDITIONS|
|Twentymile:||Closed||Closed. Forest Service is monitoring conditions.|
|Lost Lake Trail:||Open||Please stay on trail to avoid resource damage through forested areas.|
|Primrose Trail:||Open||Please stay on trail to avoid resource damage through forested areas.|
|Resurrection Pass Trail:||Closed||Closed for the 2018/19 season. Next season will be open to motorized use.|
|South Fork Snow River Corridor:||Open|
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