Storm slabs, wind slabs and cornice falls associated with the heavy snowfall two days ago are still an issue today. Although the bonding of the new snow to the old snow surface is occurring quickly, slabs and cornices may still be triggered. Yesterday there were three large avalanches seen/reported in the Turnagain Pass zone. Two of these were in Main Bowl of Seattle Creek and were storm slabs triggered by snowmachiners. One was triggered by a cornice fall and one was remotely triggered from above. The third avalanche was on the SE face of Seattle Ridge and is unknown if this was a natural slide or triggered remotely from a snowmachiner(s) on the ridge. An avalanche course heard the slide from across the valley. This third avalanche looks to have stepped down into deeper weak layers in the pack. See photos below.
For today, if visibility allows for travel to the upper elevations, know that these types of avalanches remain possible. Furthermore, cornices have grown and could break farther back than expected. It is only the 2nd day out of a storm and don’t expect all slopes to remain intact. Although triggering a storm slab or wind slab avalanche will be less likely today, these slides can be large and have high consequences. Quick hand pits and getting your shovel out to look at the new/old snow bonding is a good way to help assess the slopes you are interested in riding. Assessing deeper weak layers in the pack is more difficult – more on that below. Keeping with safe travel habits, chiefly exposing only one person at time if venturing into avalanche terrain is key. Watch your buddies closely.
Close up of the crown of avalanche above, note the dark bed surface, this avalanche ‘stepped down’ into weak snow near the ground
Yesterday a snowmachine triggered a cornice fall, which triggered this storm slab avalanche in Main Bowl (1st Bowl) in the Seattle Creek drainage.
Triggering a deep persistent slab is just as concerning, if not more concerning, as the avalanche issues in the new snow. This is because these can be larger and more destructive avalanches. Underneath the storm snow sit a variety of weak layers deeper in the snowpack. The first is the New Year’s buried surface hoar that is anywhere from 30″ to ~5′ deep (general snow depths vary widely due to wind distribution and snowfall differences). This layer was showing signs of being reactive in pits yesterday – it took a bit of force to fail, but once it fails, it’s sliding easily. There are also facets that have been found near crusts in the mid to lower pack as well as basal facets that sit near the ground. The point is, this is a complicated snowpack that just received a lot of weight – avalanches triggered deeper in the pack can be very large and unsurvivable.
Video of failure in the New Year’s buried surface hoar on Sunburst ridge, while the storm snow has bonded well in this area
Partly sunny skies filled the area yesterday with no precipitation. Ridgetop winds bumped up to the 30’s with gusts in the 50’s mph yesterday morning from the East before tapering off significantly in the afternoon and overnight have been light and variable. Temperatures remained warm, in the mid to upper 20’sF along ridgetops and in the mid 30’sF below 1,000′. A slight inversion is in place this morning with valley bottoms in the upper 20’sF.
Today, we are just on the edge of some instability showers to our Northeast. We may see partly clear skies with no precipitation, yet we may also see these showers back down our way to bring 1-2″ of snow above 1,500 and light rain (.2″) below this. Ridgetop winds are expected to be relatively light, 5-15mph from the East today and into tonight. Temperatures will stay on the warm side with mid 30’sF at 1,000′ and the upper 20’sF along the ridgelines.
Early tomorrow another warm storm system moves in from the East. As of now, the rain/snow line looks to be around 2,000′ and possibly higher. Models are showing precipitation amounts in the 1-2″ of rain and 1-2+ feet of snow up high by Wednesday night. Stay tuned and cross your fingers for a lower rain line.
*A big THANKS to the folks who cleared off the Seattle Ridge weather station yesterday!
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||0||0||60|
|Summit Lake (1400′)||28||0||0||15|
|Alyeska Mid (1700′)||33||trace||0.04||48|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||29||SE||15||30|
|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|
|01/22/20||Turnagain||Observation: Tincan||Allen Dahl|
|01/21/20||Turnagain||Observation: Tincan||Eric Roberts|
|01/20/20||Turnagain||Observation: Eddies||H. Thamm B. Edwards|
|01/20/20||Turnagain||Observation: Eddies||Andy Moderow|
|01/19/20||Turnagain||Avalanche: south facing aspect on 3800ft bump just northeast of 4940||Anonymous|
|01/19/20||Turnagain||Avalanche: Cornbiscuit & Magnum||Allen Dahl|
|01/19/20||Turnagain||Observation: Eddie’s||Kakiko Ramos-Leon|
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.