October 30th UPDATE
Get ready for some rain…! A warm, wet and windy storm is closing out October 2021 and creating dangerous avalanche conditions. After a week of chilly, and mostly benign weather, this weekend the faucet is turning on as an ‘atmospheric river‘ points our way. Between 8-10″ of rain is expected to fall in Girdwood and 6-8″ at Turnagain Pass from Friday night into Monday – wow. Ridgetop easterly winds are slated to be in the 50-90 mph range as well. The only problem for snow lovers is the rain line is looking pretty high… the National Weather Service says:
“Snow level rising from 2,500 ft today to near 3,000 ft by Saturday evening. Hazardous gusts up to 80 mph are expected by Saturday afternoon. High end snow accumulations expected above 3,500 ft.”
Avalanches are most common during and just after a storm.
A very large storm is over the region now. Large natural avalanches are likely this weekend and through the extent of the storm. These will be wet snow and glide avalanches in the mid elevation band and dry snow avalanches in the high alpine. Avalanches could send wet debris down into snow-free zones and over hiking trails. Avoiding avalanche terrain, including summer trails that have steep slopes above them is recommended.
Right now the snowpack is near zero at the parking lots at Turnagain Pass, but a good 3′ deep at 2,500′, and up to 5′ deep at 3,500′. If rain really does fall to 3,000′, this will cause a definite uptick in glide avalanche activity as well as wet snow avalanches near 3,000′. Above the rain line, in the high alpine, several feet to 6-8 feet, of new snow will cause a significant rapid loading event. It will be no surprise to see large new snow avalanches at elevations above 3,500′. That all said, it’s a good weekend to do some shopping, enjoy Halloween, watch football, or better yet, check out this awesome talk by Karl Birkeland on ‘Advances in our understanding of Avalanche Release’! It’s around 30 minutes, find his presentation HERE.
Quantitative Precipitation Forecast (QPF) is the water amount expected to reach the ground from Friday night through Monday. Below the snow line, this is the same as rain.
Infrared image of the current atmospheric river pointed at Southcentral from the GOES West satellite. Image taken 10.30.21 at 7:10am.
There was a known weak layer of facets in early October, but this layer has been buried by several feet of snow and shown only signs of healing with the warm conditions. We have not, nor have any observers, found a weak layer in the pack for several weeks. The pack is a moist homogenous layer under 4,000′, with crusts below 2,500′. Because it is so warm, the pack as a whole is oozing down the slopes creating glide cracks and many of the cracks are releasing into glide avalanches. All the avalanche activity seen recently has been these glide avalanches, which produce those tell-tale ‘brown frowns’ and ‘skid marks’. We can expect to see many more of these once the weather clears.
Glide cracks and avalanches on the SW face of Sunburst. Photo taken 10.26.21 by Isaac Swanson.
Glide cracks and avalanches on Tincan. 10.24.21.
Snowfall to date @ Turnagain Pass 2,500′ – 3,500′:
Sept 22-24 storm: 16-20″ snow, ~2 – 2.5″ of SWE
Sept 30-Oct1 storm: 12-16″ snow, ~1-1.5″ of SWE
Oct 6-8 storm: 6-8″ snow, 0.7″ SWE
Oct 11 storm: 6″ snow, 0.6″ SWE
Oct 14 storm: 8″ snow, 0.6″ SWE
Oct 17-21 storm: 20-30″ snow, 3.3″ SWE
Oct 22-23 storm: 10″ snow, 1.1″ SWE
Oct 28: 5″ snow, 0.4″ SWE
Snow depth at the Turnagain Pass SNOTEL (1880′) as of Oct 30, 6am: 30 inches
Snow depth estimated at 3,000′ as of Oct 30: 4-6 feet
Keep tabs on this Halloween storm on our weather page!
- The Avalanche Center will begin issuing intermittent snow, weather and avalanche updates as conditions warrant through mid November.
- Daily avalanche forecasts are planned to begin around Thanksgiving week.
- We will be hosting several ‘Forecaster Chats’ this December into January. Stay tuned for dates and topics.
- The best way to keep tabs on current events/information for the early season is on our Facebook page and Instagram.