Observers yesterday reported triggering small wind slabs in steep, wind-loaded terrain. Look and feel for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. Loading patterns can be very localized and it may be hard to tell where the wind effect is as new snow today covers up the evidence. There is a lot of soft snow available for transport and more on the way. Winds today could form new wind slabs and/or increase the depth of existing ones. Keep in mind the consequences of the terrain should even a small slab pull out from underneath you.
Loose Snow Avalanches: In steep terrain where winds aren’t an issue sluffs may be large enough to knock you off your feet and carry you.
Storm Slabs: Pay attention to changing conditions and to how the new snow falling today bonds to the snow below. If the snow is cohesive enough shallow storm slabs may form. Temperatures are forecast to be warmer than the previous storm so slabs may form more quickly with the density difference. Hand pits and small tests slopes will be useful ways to assess bonding.
Wind affected surface snow on Seattle Ridge. 12-15-18
We are tracking buried layers of facets and crusts that sit 1-3′ under the snow surface. These layers are more prevalent in the mid-elevations (2000’ – 2700’). Snow pit data and a lack of avalanche activity has been pointing to an unlikely chance for an avalanche releasing deeper in the pack. Additional snow load especially in the Summit area could start to tip the balance. Evaluate the snowpack and terrain as you travel. The thinner the snowpack the more suspect it is. Observers keep finding spots that whumpf on facet/crust combinations reminding us not to forget about this potential avalanche hazard.
Glide cracks are beginning to open up in many places, including Sunburst’s SW face under the weather station, SW face of Tincan Proper, Gold Pan area (behind Cornbiscuit/Magnum) and the one shown below in the Johnson Pass area. These cracks can release at any moment, as this one did below in Johnson Pass. They are not associated with human triggers and the best way to manage the hazard is to avoid being on or beneath slopes with cracks.
Johnson Pass area glide avalanche, 12-13-18. Photo:Matt McKee.
Yesterday: 1-2″ of snow fell in the morning before the system moved out around 9 am. Skies were overcast, winds were easterly 10-20 mph with gusts into the 40s. Temperatures were in the 20Fs. Overnight winds were light and temperatures remained in the 20Fs.
Today: Skies will be overcast becoming obscured as the next storm moves in. 2-7″ of snow is forecast to fall with a rain/snow mix possible at sea level. Temperatures will be in the mid 20Fs to low 30Fs. Winds will be easterly 15-25 mph with gusts into the 30s. Overnight an additional 5-10″ of snow is forecast with temperatures staying in the 20Fs to low 30Fs.
Tomorrow: Snow showers continue with calm winds and temperatures dropping into the low 20Fs as cooler air moves into the region by the afternoon/evening. Cooler temperatures and a chance of snow are the theme for the week. We will pay close attention to the next low developing over the Aleutians. Stay tuned!
*Seattle Ridge anemometer (wind sensor) is rimed over and not reporting.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||24||1||0.1||31|
|Summit Lake (1400′)||21||0||0||11|
|Alyeska Mid (1700′)||24||2||0.2||21|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||24||*no data||*no data||*no data|