Snow does not like rapid change. When rapid change occurs, weak layers have a hard time adjusting to the load. Winds overnight have brought about this rapid change. Slabs have been actively growing on leeward slopes in the higher elevations. Winds have been mainly out of the East. The important thing to remember about wind is that direction changes are common in mountainous terrain. With that said, recognition of wind loaded slopes is a better assessment tool than reading the weather station data when it comes to wind direction and loading patterns.
Shooting cracks and collapsing are obvious indicators of unstable slabs. Stiff, hollow and upside snow should be avoided today in leeward starting zones and cross loaded terrain features. These slabs could build into the 12” range and have enough volume to injure or bury a person.
A layer of weak faceted snow sits anywhere from 2-16” below the surface. This layer is widespread throughout the forecast area. This layer is deepest on the North end of Turnagain Pass (Eddies, Pyramid) where snowfall earlier in the week put down slabs up to 12” thick. Heading South along the Pass that slab gradually gets thinner and less continuous across slopes with averages in the 6-8” range. As a result we have seen more reactive snow where that slab is thicker, including remotely triggered avalanches within the last 2 days. In the Girdwood Valley we have a different setup, where older dense wind slabs 4-8” thick that formed a week ago are sitting on this weak layer and concealed by 6″ of snow that has fallen this week.
To put it simply, we have the perfect recipe for a slab avalanche in many areas today; slab + weak layer. Add into the mix the right terrain (slopes 35 degrees and greater) and a trigger (humans or rapid loading of snow) and the result is avalanches.
Avalanches could occur within newly formed wind slabs and they could also step down to this weak layer. Regardless of the actual failure layer, it will be important to avoid slopes 35 degrees and over that have this slab/weak layer combo.
A continuation of above freezing temperatures in the mid elevations along with occasional rain will make wet loose avalanches another concern today. Volume of these will be generally low. Despite this it will be important to recognize and avoid steep terrain that is holding loose, weak and damp snow. This snowpack issue becomes more concerning when traveling above terrain traps such as cliffs, gullies and trees.
The greatest change in the past 24 hours is in the wind category. Ridgetop winds picked up overnight with the Sunburst weather station averaging in the 20-30 mph range since 10 pm. Light rain and snow have been falling with the rain/snow line fluctuating between 1,500 – 2,000′. Temperatures as you might guess have been warm with ridgetops in the low 30s F.
Today expect snow and rain showers throughout the day. Rain/snow line should hover around the 1,500′ mark. Snowfall amounts will be in the 2-3 € range above this line. Winds will be out of the East at 15-20 mph with higher gusts. Temperatures will remain mild with ridgetops in the low 30s F.
The extended outlook shows a continuation of warm temperatures and precipitation. Sunday night into Monday looks to bring the next round of more significant moisture and warm temperatures to the area.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||32||1||.1||36|
|Summit Lake (1400′)||28||0||0||9|
|Alyeska Mid (1700′)||31||Trace||.1||26|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||30||NE||8||34|
|04/19/21||Turnagain||Avalanche: Triangle, Seattle creek||Will Morrison|
|04/18/21||Turnagain||Avalanche: Turnagain Pass Road Obs||Andy Moderow|
|04/18/21||Turnagain||Observation: Seattle Ridge, approximately 300 yards south of the up track||Brent Byrne|
|04/17/21||Turnagain||Avalanche: Road obs||Johnston-Bloom / Moderow Forecaster|
|04/16/21||Turnagain||Avalanche: Seattle Ridge||Wendy Wagner Forecaster|
|04/16/21||Turnagain||Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge||CNFAIC Staff Forecaster|
|04/16/21||Turnagain||Observation: Sunburst||Lance breeding|
|04/15/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|04/13/21||Turnagain||Observation: Turnagain Pass Road Obs||A Schauer Forecaster|
|04/12/21||Turnagain||Observation: Tincan||Johnston-Bloom / Latosuo 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: firstname.lastname@example.org
|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.