Saturday, January 6th 2018 4:54 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
The avalanche danger is CONSIDERABLE on all aspects and elevations above 2000’ where triggering a slab avalanches 1-3’ thick is likely today. At elevations above 3,000’ triggering a very large slab avalanche that breaks in weak snow near the ground is also possible. Cautious route-finding and conservative decision-making are essential. Sticking to low consequence terrain less than 30 degrees is recommended.
Below 2,000’ the danger is MODERATE where crusts have formed, and an avalanche releasing from above is still possible. Below 1000’ the danger is LOW where very little snow exists.
For a summary of avalanche conditions in Summit Lake click HERE.
|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.|
|Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.|
Turnagain Pass is now open to motorized use on the Western side of the Seward Highway. A Special Avalanche Bulletin has been issued due to elevated avalanche danger combined with the anticipated crowds of snowmachine traffic in the Turnagain Pass. Human triggered avalanches are likely today on slopes steeper than 30 degrees in the alpine, above treeline and alder line.
The Chugach National Forest wants to remind riders to avoid areas with thin snow cover like “Rookie Hill” and the Southern end of Turnagain Pass towards Bertha Creek. Johnson Pass remains closed due to lack of snow. You can keep tabs on the current riding status of other areas of the National Forest at bottom of this page.
Wind loading from yesterday and today is adding additional stress to an already tenuous snowpack. Several persistent weak layers are sitting under the New Year’s storm that ended on Wednesday and left 1-3 feet of snow across our region (Turnagain Pass and Girdwood.) This storm covered up a widespread layer of surface hoar that has been reactive in stability tests over the last few days. It is unknown how this layer will respond to a bigger trigger like a snowmachine. Only one steep slope has been tested by numerous skiers/boarders, Common Bowl on Tincan. No incidents were reported. Otherwise very limited information exists as to how well the snowpack is adjusting to it’s new load. We also don’t know how intact the surface hoar remains across any given slope.
Be aware of newly forming wind slabs on leeward features. These slabs are like to be small and isolated, but could have high consequences should someone initiate a wind slab that steps down to a deeper layer of the snowpack. Wind loading is an additional reason we urge folks to use caution and chose low consequence terrain in the alpine, slopes less than 30 degrees in steepness.
Today keep in mind:
- Several tracks (snowmachine, ski, or snowboard) may be on a slope before someone triggers an avalanche
- Remote triggering from the top, side or bottom of a slope is possible
- The larger the slope the larger the avalanche
- Obvious signs like “whumpfing” and shooting cracks may or may not be present.
*In addition to the buried surface hoar problem, weak faceted snow sits near the ground in avalanche paths that released in early December. Places like the SW face of Sunburst and Seattle Creek Headwall are suspect of this structure.
Propagation potential has been found in stability tests during and after the storm on a widespread layer of surface hoar.
In the Alpine, above 3,000’, a human triggered, large and dangerous deep slab avalanches is still possible. A hard slab, 3-5+ feet thick sits on weak sugary snow (basal facets) near the ground. This is a high consequence avalanche problem that is impossible to outsmart, and will take a long time to heal. A big trigger like a snowmachine or a slab avalanche in the upper layers of the snowpack may be enough force to initiate a deep slab avalanche. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.
Yesterday skies were clear and Easterly ridge top winds increased in the afternoon to Moderate. Sunburst weather station averaged 14mph with a few gusts in the low 40s mph early this morning. An inch of snow was recorded overnight at Center Ridge Snotel in Turnagain Pass and temperatures have increased from the low 20F’s to 30’s F at 1000’ this morning.
Today 1-4” of snow is possible (.2” SWE) and Moderate Easterly winds are expected to decrease by late afternoon. Skies should remain overcast with limited visibility. Temperatures should remain in the low 30F’s at 1000’, and rain/snow could reach 600’.
Snow flurries are possible tomorrow, but minimal accumulation is expected. Temperatures will be in the mid 20F’s and winds should be light and variable. Clearing skies and cooler temperatures are expected Monday into Tuesday.
PRECIPITATION 24-hour data (6am - 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880')||27||1||.1||44|
|Summit Lake (1400')||13||0||0||16|
|Alyeska Mid (1700')||25||trace||.04||36|
RIDGETOP 24-hour data (6am - 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
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 firstname.lastname@example.org
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.