High winds yesterday afternoon through midnight, sustained around 40mph with gusts over 70mph, raked the mountains, scouring windward slopes and depositing a combination of new snow and existing snow onto leeward slopes and catchment zones. Even the mid and lower elevation snow saw substantial wind transport. There was likely a peak in natural wind slab acivity and HIGH danger at the tail end of these strong winds overnight.
Wind slabs that were just starting to be formed yesterday were 4-10” thick, very sensitive and could be cracked out and released with the slightest touch. Because these slabs have formed on very weak sugary snow they are not likely to bond anytime soon.
Steering clear of ANY wind deposited snow on slopes over 30 degrees will be prudent. These areas may not be obvious as 1-3” of new snow forecast with little wind today could mask these monsters. Remotely triggering a slope (i.e., from below or a flat area) is possible. Collapsing and cracking should be widespread – if you are on a slope steep enough it will probably avalanche.
Though the forecast for 2 feet of snow by this morning was a bust and yesterday evening’s quick and dirty onslaught was finished around midnight, the 8-12” of new dense snow above treeline is highly unstable. Not only did the storm come in cold and leave warm (creating an unstable upside down storm layer), it fell on extremely weak faceted snow – ball bearings – that will have little chance of allowing the new snow to stick to the sides of the mountains. Hence, areas lacking a wind slab will still be likely to avalanche with just the new layer of storm snow.
Snowfall numbers (storm total as of 6am 12/9):
Turnagain Pass SNOTEL 1880′: 9 € snow, .7 € water
Summit Lake SNOTEL 1400′: 3 € snow, .3 € water
Alyeska mid mtn: 10 € snow, .8 € water (1.2 € water at 2800′)
The leading edge of the first “real” storm system for over a month moved through quickly yesterday evening with strong easterly winds (sustained 40mph, gusting 70’s) and heavy snowfall in Eastern Turnagain Arm. As the storm weakens today there is a chance for another 1-3 € as well as a few more inches for Monday. The easterly winds have decreased substantially since midnight and should be in the 10-20mph range on the ridgetops today. Temperatures around treeline increased from ~20F yesterday to the upper 20’s today where they should remain. There is a light rain/snow mix this morning at sea level along Turnagain arm with slippery roads.
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).
Kevin will issue the next advisory Monday morning, December 10th.
|05/06/20||Turnagain||Avalanche: Pastoral Peak, north face||Andy Duenow|
|04/10/20||Turnagain||Avalanche: Wolverine||Mike Records|
|04/10/20||Turnagain||Observation: Eddies lookers right shoulder||Matt Yoder|
|04/09/20||Turnagain||Observation: Bench Peak||Mike Records|
|04/04/20||Turnagain||Observation: Pete’s North||Anonymous|
|03/26/20||Turnagain||Avalanche: Tincan – Proper (SW facing)||CNFAIC Staff|
|03/26/20||Turnagain||Avalanche: Seattle Ridge||W Wagner Forecaster|
|03/25/20||Turnagain||Avalanche: Sunburst Uptrack @ 2000′||J. Boisvert|
|03/24/20||Turnagain||Observation: Turnagain – Road Observations||W Wagner Forecaster|
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.