Deep southerly flow yesterday brought .4- 1.1” of water (4-12” of heavy, wet snow above 1,500’) across the eastern Turnagain Arm region with the Girdwood and Portage valleys being favored. Any new snow fell on a stout melt-freeze crust and the big question today is ‘how well is the new snow bonding to this pre-storm surface’? It’ll be prudent to ease in to terrain today and seek out small no-consequence test slopes to investigate the storm/ crust interface. Quick hand pits will also help distinguish how this interface is acting. With an increase in elevation expect to move from more of a wet snow avalanche problem to a wind slab avalanche problem in the upper elevations.
Heavy, wet snow was plastering to all windward surfaces yesterday including this vehicle in the motorized parking lot at Turnagain pass. photo: Ryan Lewthwaite
Wet avalanches: These can be easy to initiate in steep terrain (greater than 35 degrees) and will have the potential to entrain a significant amount of storm snow while gaining mass and momentum. These can be particularly dangerous when paired with a terrain trap. Unseasonably warm temperatures today, rain on snow or direct sun will further act to promote wet avalanches failing naturally.
Wind slabs: A brief period of wind toward the end of the storm yesterday likely built tender wind slabs in the alpine. These may be touchy, particularly on leeward (south and west), wind-loaded slopes. Expect wind slabs to be in the 16-24” range, again deposited on a stout melt-freeze crust that was found up to ridgetops before the storm.
With warming temperatures today and through the week, we could see another spike in glide avalanche activity. Glide cracks have been avalanching, several per day over the last couple of weeks with at least a couple caught on video HERE and HERE. Avoidance of the crack is best; but easier said than done at this point with glide cracks threatening very popular and well-traveled backcountry routes on both sides of the highway thru Turnagain pass. Continue to maintain vigilance and limit your exposure to slopes with glide cracks.
Cornices warrant mention today as well. We haven’t seen a real active day of widespread cornice failure yet this season. This just means they continue to grow and creep closer to failure. Warming temperatures this week could act as a catalyst for cornices to fall. Keep a wide berth both on ridges and when moving below corniced terrain.
Moisture-rich southerly flow moved into the region Sunday night bringing storm clouds and consistent rain/ snow showers throughout the day yesterday. Girdwood and Portage saw the lion-share of moisture with over 2 € of water since Sunday evening. The rain/ snow line was generally between 1,000 €“ 1,500′ with a bit of wet snow falling as low as a couple hundred feet yesterday morning. Temperatures at Turnagain Pass averaged in the mid-30’s F at 1,000′ with winds generally light from the northeast before picking up yesterday in the late afternoon. Gusts late last night hit 64 mph at the Sunburst weather station (3880′) before dying off after midnight.
The moisture looks like it’ll mostly shut off today as the main band of precip moved just east of us overnight. Temperatures will continue to warm into the mid-30’s at 3,000; some of the warmest temperatures we’ve seen all winter are forecasted this week. Winds will be light (10-20mph) from the SE with perhaps just a few light rain showers this morning.
Another wave of moisture moves in late tonight and tomorrow before we see a day of drying on Thursday.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||33||4-6||.4||129|
|Summit Lake (1400′)||35||1-2||.1||42|
|Alyeska Mid (1700′)||32||7-12||1.1||119|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||SE||28||61|
|04/16/21||Turnagain||Avalanche: Seattle Ridge||Wendy Wagner Forecaster|
|04/16/21||Turnagain||Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge||CNFAIC Staff Forecaster|
|04/16/21||Turnagain||Observation: Sunburst||Lance breeding|
|04/15/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|04/13/21||Turnagain||Observation: Turnagain Pass Road Obs||A Schauer Forecaster|
|04/12/21||Turnagain||Observation: Tincan||Johnston-Bloom / Latosuo Forecaster|
|04/10/21||Turnagain||Observation: north sides||lance breeding|
|04/09/21||Turnagain||Observation: Girdwood to Turnagain Road Observations||W Wagner Forecaster|
|04/05/21||Turnagain||Avalanche: Resort bowl Seattle creek head wall||Clint Kyffin|
|04/04/21||Turnagain||Observation: Center Ridge||Andy Moderow|
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: firstname.lastname@example.org
|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.