Today Northwest ridgetop winds are expected to be in the 15-30mph range with gusts in the 40’s this afternoon. Loose surface snow (4-8” deep) can still be found in the heart of our forecast zone in the mid elevations and protected areas of the Alpine. Should winds reach the higher side of this spectrum, wind slabs 1-2’ thick will be likely to trigger on steep slopes. These slabs could be soft or hard, and may be forming on top of older wind slabs that exist on a variety of aspects. A brief wind event on Monday night (2/27) caused a natural avalanche cycle on the Southern end of our forecast zone (Lynx Creek to Summit Lake) with wind slabs ranging in the 12-20” deep. Its important to note that a NW flow can funnel winds through Turnagain Pass from a variety of directions and it’s not uncommon to see Southerly winds on the non-motorized side of the road. Today’s avalanche danger will depend on how strong the winds reach and how much snow is available for transport in the area you are traveling in. If large plumes of blowing snow are observed, this could add stress to existing weak layers deeper in the pack, and make it easier to trigger a deeper more dangerous slab. More details in Secondary Concerns. Shooting cracks will be an obvious clue that wind slabs are tender.
Questions to keep in mind on today:
A wind slab that failed upon isolation in a compression test on the North ridge of Silvertip yesterday afternoon. This particular ridge was impacted significantly by the Monday night wind event.
Monday/Tuesday winds were likely enough to overload the February 9th buried surface hoar layers on the southern end of the advisory area. This layer has been found to be quite a bit shallower (12 – 20” deep) on the southern end of Turnagain Pass, making it easier to trigger. In areas with a deeper overall snowpack (Seattle ridge, Tin Can, Sunburst, Girdwood Valley) this persistent weak layer is 2’-3’ below the surface and has been tougher to trigger in stability tests, but does continue to show the potential to fail and propagate.
Should strong winds occur today, the Feb. 9th buried surface hoar could be closer to its tipping point. Winds today could also be creating more trigger spots -thinner areas of the snowpack – scoured terrain features and rocky area. This type of avalanche is likely to break above you and propagate further than expected. Be aware that no red flags may be present.
Deep Persistent Slab: We continue to find various layers of weak faceted snow and depth hoar near the bottom of the pack in certain areas. This includes Summit Lake zone, and some areas in Girdwood Valley and towards the Southern end of Turnagain pass, near Johnson Pass and Lynx Creek. Similar to the problem above, these layers will be very tough to trigger, but a possibility remains in places with this poor structure.
A natural avalanche on the SW shoulder of Captain’s Chair that was triggered naturally during Monday/Tuesday’s wind event. Due to how wide this avalanche propagated the suspected weak layer is the Feb.9 buried surface hoar. This avalanche ran 1000 vertical feet – note the debris in the lower left corner.
Cornices: Winds today may add stress to already large cornices. These unpredictable hazards can release naturally and break farther back onto a ridge than expected. They also have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them.
Yesterday skies were partly cloudy and temperatures ranged between 0F and 15F. Winds were light from the NE and no precipitation was recorded. Overnight temperatures dropped back to around 0F and winds were light.
Today expect clear and sunny skies, and similar tempatures 0F-15F. Northwest ridgetop winds will increase late morning to 15-30mph and gusts may reach the 40’s mph. This wind event is expected to peak this evening, but moderate winds are expected to last through tomorrow evening.
Cold temperatures associated with a high pressure system over interior Alaska will continue to be our dominant weather pattern. This pattern will dominate Southcentral, Alaska into next week without much on the horizon of major changes in the extended forecast.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||3||0||0||64|
|Summit Lake (1400′)||1||0||0||30|
|Alyeska Mid (1700′)||8||0||0||59|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||4||NE||7||21|
|01/26/20||Turnagain||Observation: Pastoral||Allen Dahl|
|01/26/20||Turnagain||Observation: Tincan trees and north side Tincan Ridge||Joe Kurtak, Anchorage Nordic Ski Patrol|
|01/25/20||Turnagain||Observation: Magnum||Ryan Van Luit Forecaster|
|01/25/20||Turnagain||Observation: Tincan||Eric Roberts/ Kakiko|
|01/25/20||Turnagain||Avalanche: Sunny Side of Seattle||Peter Wadsworth|
|01/23/20||Turnagain||Observation: TIncan||Eric Roberts|
|01/23/20||Turnagain||Observation: Goldpan||Allen Dahl|
|01/22/20||Turnagain||Observation: Sunburst||Adrian Beebee|
|01/22/20||Turnagain||Observation: Sunburst||Ryan Van Luit Forecaster|
|01/22/20||Turnagain||Observation: Seattle Ridge||W Wagner Forecaster|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: email@example.com
|Area||Status||Weather & Riding Conditions|
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.