There were only a couple reports from the mountains during the storm yesterday, one was from John Sykes (forecaster) at Pete’s South and the other from a group in Placer Valley. Both parties reported storm slab avalanches that were easy to trigger. They stayed in the trees due to the stormy weather and avalanche concerns, but in the smaller terrain they could trigger slabs up to a foot deep at Pete’s South and over 2′ deep in Placer Valley where more snow has fallen.
Small storm slab avalanche on Pete’s South. Slab was skier triggered at 1700′ on a west aspect, about 12″ deep and 50′ wide. 1.28.22.
|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
Wow, what a few days of snowfall. Light to heavy snow has been falling since Wednesday afternoon with the highest rates seen yesterday. Snowfall totals over the past 24-hours were 18-24″ for mid/upper elevations in Girdwood and Placer Valleys and 12-14″ for Turnagain Pass. Check out the table below for the storm totals since Wednesday. Ridgetop winds have been fairly moderate out of the east until last night when they took a jump for 6-8 hours blowing 40-50mph with gusts over 70mph. All this new snow with those winds last night will keep storm snow avalanche issues front and center, especially wind slabs!
Storm total estimates for 2,500′ beginning Wednesday afternoon through last night:
Turnagain Pass: 14-22″ (1.4″ SWE at Center Ridge 1,800′)
Girdwood Valley: 24-36+” (2-3″ SWE)
Placer Valley: 24-36+” (~3″ SWE)
Summit Lake: 2-4″ (0.2 SWE)
For all those headed out today- the storm has just ended. We need to ease into terrain and not let powder fever get the best of us. Be sure to pay close attention to slopes with recent avalanches, and the other signs of instability (cracking in the snow around you and whumpfing). The deeper the new snow, the larger the potential avalanche. Safe travel practices are a must. Expose only one person a time, watch your partners, and have escape routes planned. Although the storm snow should be in the process of stabilizing, it can take a couple days.
Wind Slabs: These are likely to be easy to trigger and could be larger and more dangerous than expected. They could be anywhere from 1-3+ feet deep. Watch for signs of wind effect and steer clear of slopes and cross-loaded gullies with wind loading.
Storm Slabs: It will still be possible to trigger storm slabs similar to those yesterday on slopes out of the wind, including slopes in the trees. Storm slabs could be 1-2′ deep depending on how much snow fell in the area you are in. There is crust up to ~2,000′ under the new snow and this could slow the bonding in the mid-elevations.
Sluffs (loose snow avalanches): On slopes out of the wind, expect to trigger sluffs in the new snow. These could entrain a large amount of snow in larger terrain.
Cornices: Be extra cautious on ridgelines as cornices could be teetering on the brink of failure. They could trigger an avalanche below and potentially put others in harms way.
Cracking on a small test slope yesterday on Pete’s South. 1.28.22.
Persistent Slab: In addition to the storm snow avalanche concerns, there is an outside chance that a person could trigger a larger avalanche on weak snow near the New Year’s crust. This would now be buried 2-6+′ deep. This is a tricky problem with high uncertainty and low likelihood. The only known activity on this layer was a large human-triggered avalanche on Tincan Proper over a week ago (details here). As we head into a clear period and the storm snow stabilizes, we need to keep this issue in our minds.
Yesterday: Moderate to heavy snowfall across the forecast area. Girdwood/Placer/Portage Valleys saw the higher past 24-hour accumulations of 18-24″. Turnagain Pass was closer to 12-14″. Rain snow line crept up to 200-300′ overnight. Ridgetop winds were easterly, 20-25mph during the day and reaching 40-50mph around midnight with stronger gusts. Temperatures hovered in the 20’sF at the mid and upper elevations with sea level creeping into the mid 30’sF.
Today: The stormy weather is pushing out this morning and there is a chance for some clearing skies. A trace to no precipitation is forecast. Ridgetop winds have quieted down as well and slated to be 5-10mph out of the northwest today. Temperatures are in the 20’sF at most locations with lower elevations close to 30F.
Tomorrow: Mostly clear skies are expected for tomorrow and Monday with this break in storms. Ridgetop winds look to be light and variable. Temperatures should be cooling off to the teens and single digits in valley bottoms.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||13||0.8||98|
|Summit Lake (1400′)||26||0||0||35|
|Alyeska Mid (1700′)||30||18||1.2||N/A|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||SE||8||20|
|11/25/22||Turnagain||Observation: Sunburst||Hannah Smith|
|11/25/22||Turnagain||Observation: Sunnyside / Seattle Ridge||Matti Silta|
|11/25/22||Turnagain||Observation: Sunburst||John Sykes|
|11/25/22||Turnagain||Observation: Tincan Trees||Andy Moderow|
|11/25/22||Turnagain||Observation: Tincan||Galen Hecht|
|11/25/22||Turnagain||Observation: Top of Seattle Ridge uptrack||Nick Crews|
|11/24/22||Turnagain||Avalanche: Sunnyside/Main Bowl||Andy Moderow|
|11/23/22||Turnagain||Avalanche: Seattle Ridge||John Sykes Forecaster|
|11/23/22||Turnagain||Observation: Tincan Trees||Brooke Edwards|
|11/23/22||Turnagain||Observation: Tin Can Common Bowl||Melanee Stiassny|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: email@example.com
|Area||Status||Weather & Riding Conditions|
This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.