Easterly winds blowing 15-30 mph with gusts into the 50s overnight will have moved any soft storm snow left available to transport into leeward areas. Additional snow falling today may also get blown around with 1-4″ in the forecast. Wind effect from the very strong winds during the wet storm on Friday and Saturday was evident in the Alpine yesterday. However, there was minimal signs of wind slab. Today that may have changed, wind-loaded, steep unsupported slopes above 2500′ may be tender. Look for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. Loading patterns can be very localized and it is crucial to look for clues indicating where the snow is being distributed.
Wind effect on the Tincan uptrack, 12-9-18
Observations yesterday in Turnagain Pass found signs that the storm snow is bonding well to the old snow surfaces. We do not have evidence that there currently is a persistent weak layer issue in the this core area of the advisory zone. Above 2,500′ there is a thin layer of buried surface hoar anywhere from 2-5′ deep in the snowpack but it is not showing signs of reactivity and at this point is being regarded as a dormant layer to track. As we move south and the 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 in Summit Lake. If traveling in this area the likelihood of triggering a dangerous avalanche remains. Choose terrain carefully.
Red flags to watch for:
– Recent avalanches
– Whumpfing (collapsing) of the snowpack, a sign to avoid avalanche terrain.
– Shooting cracks, likely to be seen near ridgelines where the wind has formed wind slabs.
Summit snowpack observation: Tenderfoot, 12-3-18
Yesterday: Skies were mostly clear and sunny. Temperatures were in the 20Fs to mid teens. Winds during the day were light and variable. Overnight easterly winds picked up blowing 15-30 mph with gusts into the 50s. Temperatures initially cooled into the evening and then rose again in the early morning into the 20Fs and low 30Fs.
Today: Cloudy skies and snow showers throughout the day. 1-4″ of snow above 300′. Easterly winds 10-20 mph with gusts into the 30s. Temperatures in the low 30Fs to mid 20Fs. Continued snow showers overnight with snow to sea level, 2-5″.
Tomorrow: Continued snow showers with more cold air moving into the region Tuesday night. From the National Weather Service: The colder air which moved across the Gulf and Southcentral yesterday was the beginning of what appears to be a prolonged shift to a more “typical” Alaska weather regime for this time of year. There are a number of features in the forecast that we will keep tabs on for the week! Stay tuned. Timing and precipitation amounts are still uncertain.
*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||26|
|Summit Lake (1400′)||19||0||0||4|
|Alyeska Mid (1700′)||24||0||0||
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||20||*no data||*no data||*no data|