Wind Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–2
Through rain and snow, Santa appeared,His sleigh aglow, his reindeer cheered.“Christmas comes, whatever may fall,Be it rain, or snow, or none at all!”
Happy Holidays everyone! After a week of rain down low and snow up high we could see a short break in weather this afternoon before a few more inches of snow falls Thursday (to 500' possibly). This morning ridgetop winds are still blowing 15-20 mph with gusts near 30 from the east but should lighten up later today. A few inches of snow fell yesterday to 1,000', which sits on a freezing rain crust that transitions to just dry snow higher in elevation. With strong winds last night, wind slab avalanches and cornice falls will be the main concern for anyone headed out in search of dry snow in the upper elevations.
Today will be a day to look for active wind loading and areas the previous winds have loaded slopes and grew cornices. New wind slabs should be fairly easy to identify by watching for smooth rounded surfaces, stiff snow over softer snow, and of course cracks that shoot out from you. They could be anywhere from 6" to a couple feet deep. How quickly these will bond is the question and since they could be less than 24 hours old, that's well within the window of still being easy to trigger.
With all the weather over the past week there is likely to be multiple generations of wind loading. Hence, wind slabs could be very deep in some places. Additionally, a week ago before all the snow, a layer of surface hoar existed that was destroyed where it rained and where the wind blew it down. But... it may have survived in some high elevation wind sheltered zones. Something to keep in mind when skies clear and folks head out to the higher and less traveled terrain. If this is the case, a surprise large avalanche could be triggered.
Holiday storm cycle snowfall estimates from Thursday through Wednesday morning above 2,500' with rainfall amounts below 2500':
- Girdwood: 24-36+" snow (4-5.5" water)
- Portage: 40 -60+" snow (15" water)
- Turnagain Pass: 20-36" snow (4.2" water)
- Summit Lake: 7-9" snow (0.8" water)
- Seward/Lost Lake: 14-20" snow (2.1" water)
Wet snow avalanches? In the mid elevations, where rain fell for several days, the wet snow is beginning to freeze as temperatures cool slightly. Because of this, we don't expect wet snow avalanches to be an issue.
(12/24/2024)
Skin track near the top of treeline on Tincan, looking across Turnagain Pass to Seattle Ridge. A few inches of snow is covering the rain crust making for more enjoyable turns in the mid elevations.
Photo: Caleigh Warner
