Triggering a 1-2′ thick slab avalanche on slopes 35 degrees and steeper is likely today. Wind loaded slopes are the most suspect. Yesterday the advisory area saw steady snowfall with an additional 4-10″ of snow (favoring Girdwood) and easterly wind loading throughout the day. Sunburst saw gusts into the 80s and Max’s into the 60s. Observers noted cracking and small test slopes being easily triggered later in the day. Visibility made Alpine observations difficult. The strong winds eased off in the evening and there was a break in the snowfall. Snow started again early this morning and is forecast to continue today throughout the advisory area. The old wind harden snow surface from before the storm and Saturday’s low-density snow will make it tough for the new snow to stick right away. ‘Upside-down’ snow was noted by observers yesterday. Today look for recent avalanches, shooting cracks and listen for whumpfs or hollow sounding snow. Choose terrain carefully. Cornices may be quite tender and should avoided.
Storm slab triggered on Sunburst at 1300′, 2-17-19. Photo: Elliot Gaddy
Storm slabs triggered on Tincan later in the day, 2-17-19. Photo: Ray Koleser.
New snow and wind loading have the potential to add stress to underlying weak layers. As we have been hammering home for weeks, in Turnagain Pass roughly 1-3′ below the snow surface sits a layer of buried surface hoar. Periphery zones such as Summit Lake and Johnson Pass harbor a poor overall snowpack structure with a variety of weak layers. Although these persistent weak layers have not been reactive lately, additional load may start to tip the balance. It is good to keep in mind that triggering an avalanche today could to step down into old weak layers and initiate a larger more dangerous slide. This is more likely in Summit Lake and the central Kenai mountains.
Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time. The best way to manage this problem is to avoid traveling on slopes directly below glide cracks.
Yesterday: Skies were obscured with snow falling throughout the day. Winds were easterly 20-40 mph gusting as high as 88 mph on Sunburst. Temperatures were in the 20Fs to mid 30Fs. Overnight skies were mostly cloudy and winds were easterly 5-15 mph gusting into the 20s.
Today: Mostly cloudy skies and snow showers, 3-8″ of snow forecast. Rain/snow line around 700′. Temperatures in the 20Fs to mid 30Fs. Winds will be southeasterly 5-15 mph with gusts into the 20s. Light snow showers continue overnight with temperatures cooling into the low 20Fs.
Tomorrow: Skies clearing in the early morning becoming mostly sunny. Winds shifting to the northwest and increasing to 20-30 mph with gusts into the 40s. Temperatures will be in the low to mid 20Fs. The next storm system is forecast to move into the area Wednesday afternoon.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||29||2||0.3||62|
|Summit Lake (1400′)||30||2||0.2||28|
|Alyeska Mid (1700′)||29||5||0.6||58|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||E||13||38|