Human triggered (skier or snowmachiner) storm slabs are likely today on slopes steeper than 30 degrees. The first in the series of storms forecast to impact the area is moving out this morning. The storm brought sustained strong winds yesterday and last night and heavy snow overnight. Do not let the potential for decent visibility today lure you into avalanche terrain. Look for signs of instability. Recent avalanches are the best clue that the snowpack is unstable.
24-hour precipitation and wind:
With the strong winds and new snow we expect a buffet of storm related avalanche issues today. New snow was landing on a layer of surface hoar and may not bond well to the old snow. The temperatures increased during the storm putting heavier snow over lighter snow. Storm slabs may be very sensitive. Look for cracking and collapsing. With the buried surface hoar potential these slabs may be very reactive even on slopes in the Tincan Trees. Remote triggering may be possible. Avoid travel in runout zones.
Wind slabs: Strong winds will have the blown snow into the leeward start zones. Due to the high wind speeds slabs may have formed further down the slope than expected. Look for pillowing, drifting and cracking. Be suspect of hollow sounding snow or hard snow over soft snow.
Cornices: High winds and blowing snow will have added to already large cornices. These may be very sensitive and a cornice fall could trigger a large avalanche on the slope below. Remember these can break further back than expected.
Heavy snow overnight on Turnagain Pass.
Surface hoar observed 12-28-18, Photo: Trip Kinney
Glide avalanches have been releasing over the past week. Remember these avalanches are not triggered by people and are unpredictable. The most recent release of a glide crack (glide avalanche) was noted Saturday on Lipps. The new snow may have covered some of the glide cracks up. Don’t forget they are looming over popular ski and snowmachine terrain and limit as much time under them as possible! The glide cracks are on the move… Don’t mess with the brown frown!
Lipps glide avalanche, 12-29-18. Photo: Andy Moderow
South of Turnagain: As we have been mentioning for some time, a shallow and poor snowpack structure exists in the Summit Lake zone. Buried weak layers of facets associated with crusts sit 1-3′ below the surface near the base of the snowpack. Although Summit did not get much precipitation in this first storm it will be important not to forget the possibility of triggering a larger avalanche that could release near the ground if recreating in that zone. Check out the Summit observations HERE for the most current information.
Yesterday: Skies were overcast to obscured with snow and rain showers throughout the day intensifying overnight. Rain/snow line was around 500′. Winds were easterly 25-40 mph gusting as high as 102 on Sunburst. Temperatures were in the 20Fs to mid 30Fs.
Today: Skies will be mostly to partly cloudy. There is a chance of snow showers during the day. Winds will be easterly10-20 mph with gusts into the 30s. They shift to the north this afternoon and ease up briefly. Temperatures will be in the high 20Fs to mid 30Fs. This evening the next storm moves into the area with easterly winds increasing 20-40 mph gusting into the 50s. Precipitation may be heavy again with rain/snow line around 800′-1000′.
Tomorrow: Rain and snow in the morning decreasing in the afternoon. Winds will decrease as well. Temperatures will be in the high 20Fs to high 30Fs. The pattern remains active for the week but the model confidence remains low. Stay tuned for storm details.
*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||30||15||1.3||67|
|Summit Lake (1400′)||30||3||0.3||15|
|Alyeska Mid (1700′)||30||20||1.5||55|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||*N/A||*N/A||*N/A|