This storm pushed us into a deep slab problem at higher elevations. This means that we now have average slab depths of greater than 1 meter sitting on top of a persistent weak layer. The avalanche implications are the same as we’ve been seeing, but the volume and destructive force have increased.
With deep slab concerns a backcountry traveler will probably not see obvious signs of instabilty (whumphing, shooting cracks) until the slab actually avalanches. It is unlikely to be triggered at the deep points, but rather at the thinner edges near scoured ridges or exposed rocks. It may propagate large distances where it then pulls the deeper pockets. It may allow multiple tracks before somebody finds the trigger point and avalanches the entire slope.
Deep slab is a low probability, high consequence problem. With continued precipitation, warm temperatures, and high wind – steep terrain should be avoided. When active weather abates the safe terrain options will get better with time.
Below 2000 feet we had significant rain on snow on Friday. We can expect more rain today, perhaps as high as 1200 feet. The photos below show an example of the abnormal avalanche activity that can happen with rain and warm temperatures. This is fairly low in the Tincan trees. 3 distinct pockets released sympathetically on the steeper rolls as the weak layer collapsed. Debris from this was very dense.
Tincan avalanche 1550 ft elevation. 200 feet high by 1000 feet wide. 2-3 feet deep.
Friday’s storm deposited over 2 feet of snow at high elevations and over 3 inches of rain or snow water equivalent at some low elevations. Saturday gave us a break in the storm, but temperatures did not drop significantly.
Today, more rain and snow is expected. Another pulse of moisture is approaching from the south, originating at a deep 956mb low pressure center. Up to another inch of water is forecasted for the next 24 hours, with the bulk of that precipitation happening tonight. Temperatures will increase throughout the day, and snow level will rise from 500 feet to 1200 feet. Look for a southeast wind 51-74 mph, also increasing slightly as the day progresses.
Expect continued warm temperatures through the week with more rain and snow possible.
Current satellite image.
|01/15/21||Turnagain||Observation: Sunburst||Schauer/ Wunnicke Forecaster|
|01/13/21||Turnagain||Observation: Tincan||Johnston-Bloom / Moderow Forecaster|
|01/13/21||Turnagain||Observation: Center Ridge Meadows||Alaska Avalanche School Rec Level 1 Roberts|
|01/12/21||Turnagain||Avalanche: Seattle Ridge/Center Ridge||A Schauer Forecaster|
|01/11/21||Turnagain||Observation: Tincan Trees||Schauer/ Roberts Forecaster|
|01/10/21||Turnagain||Observation: Center Ridge Meadows||Alaska Avalanche School Pro 1 Course Latosuo|
|01/10/21||Turnagain||Avalanche: Tincan trees||Anonymous|
|01/09/21||Turnagain||Observation: Johnson Pass||Anonymous|
|01/08/21||Turnagain||Observation: Sunburst meadow between Hemlocks||Anonymous|
|01/08/21||Turnagain||Avalanche: Seattle Ridge||Wagner / Schauer|
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.