It’s been snowing – a lot! Anchorage got a significant dump last night. That snow extended to Girdwood and beyond. This is the kind of maritime storm pattern that we are famous for, and we’ve been missing during this drought winter.
The storm snow problem is least stable during the active part of the storm, and tends to stabilize quickly over time. The big message today is that we got a LOT of snow and it will need time to settle out, bond, and stabilize. We are still within the 24 hour window since active storming, and still within the window of high probability to trigger avalanches in the new storm layers.
Storms also create wind slabs and build cornices. Cornices are likely to be bigger and less stable than they were last weeekend.
Time will make these storm layers stable, but today is not the day to test them in big and dangerous terrain.
Underneath all the fresh snow from the last 5 days is the prominent crust layer that formed in February. Just above this crust is a weak layer of faceted snow mixed with buried surface hoar.
We did some snow pit testing yesterday. Results indicated the most concerning weak layer (above the Feb. crust) is difficult to initiate, but propagation potential is high. The triggering is difficult because our slab layer (40-50 inches of new snow) is thick and strong. This information tells us that avalanches may be difficult to trigger, but when they do the resulting avalanche can be large and deep.
This kind of deep slab problem is most likely to be triggered from an area of shallower snow. Wind loading patterns during the storm caused scoured ridges which quickly transition to deeply loaded slopes on the downwind side. A skier or snowmachiner is more likely to trigger this problem near the scoured ridge than far into the deep pocket. Once initiated, it could propagate across into the deeper snow.
Larger triggers are also more likely to initiate the deep slab. Snowmachines have the disadvantage here with 600+ pounds of sled and rider weight impacting the slope.
This has been a great week for snowfall. Turnagain Pass more than doubled the total snow on the ground from 42 inches on Sunday to 88 inches last night. Total new snow water equivalent is 5.9 inches. Wind during the storm was predominately from the east on Sunburst. Rain did reach up above 1000 feet at times during the storms, but the snow dried out at the tail end of the storm all the way to sea level.
Last night we got a final shot of snow during a cooling temperature trend. This last bit of the storm was widespread from Anchorage to eastern Turnagain Arm.
A chance of snow continues today, with a couple more inches possible. Decreasing clouds through the day may allow the sun to poke through at times. Temperatures should be cooler, in the low 20s. Wind will be light from the south.
|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.