Leeward, steep, unsupported slopes above 2500′ may still harbor wind slabs today from the winds Sunday night/Monday morning. 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 with the few inches that fell yesterday and overnight. Another 2-5″ is forecast to fall today.
Additionally, pay attention to how new snow falling today bonds to the snow below. As the inches slowly stack up over the hard wind-blown snow surface or over the melt-freeze crust at lower elevations loose snow avalanches may be a possibility in steep terrain. If the snow is cohesive enough shallow storm slabs may form. Hand pits and small tests slopes will be useful ways to assess bonding.
Wind effect in Tincan Common, 12-9-18
As is often the case we are concerned with the snowpack in the periphery zones of our advisory area, Crow Pass and Summit Lake. Where the Alpine snowpack is shallower, the potential to trigger a persistent slab avalanche on weak snow near the ground increases. Observations prior to the storm showed weak facets near the ground in Summit Lake. We have limited information from north of Girdwood but suspect a weak set-up. If traveling to these areas the possibility of triggering a dangerous avalanche remains. Choose terrain carefully.
Red flags to watch for:
Yesterday: Skies were cloudy with snow showers throughout the day. Temperatures were in the 20Fs to low 30Fs. Winds were easterly 5-15 mph with gusts into the 30s. Snow showers continued overnight, winds were light and temperatures dropped a few degrees.
Today: Snow showers continue with 2-5″ forecast to fall today with an additional 2-6″ tonight. Temperatures will start in the mid to high 20Fs and drop slowly throughout the day into the low 20Fs and teens tonight. Winds will be variable and light.
Tomorrow: Snow showers and cooler temperatures are the trend for the week. Thursday may see a brief window of clearing. The pattern remains active into the weekend. Stay tuned as we watch storm tracks and temperatures!
*Seattle Ridge anemometer (wind sensor) is rimed over and not reporting.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||29||4||0.4||29|
|Summit Lake (1400′)||27||1||0.1||5|
|Alyeska Mid (1700′)||28||3||0.3||12|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||*no data||*no data||*no data|