Yesterday marked the second, and most intense, period of rain on snow. Many wet loose avalanches were observed on all aspects along with two wet slab avalanches between 1500ft to 3000ft (photos below). Today precipitation is expected to decrease with potentially .3-.5″ of rain falling below 2500ft.
Wet avalanches are common during extended periods of rain and warm temperatures. They typically start on steep terrain with rollerballs initiating under cornices, trees, rocks or underfoot that subsequently entrain more and more snow as they gain momentum and move downslope. If caught in a wet avalanche it is very difficult to escape as the heavy wet snow can quickly knock you off your feet, twist a knee or break a leg. Debris has the potential to run further than expected due to a melt/freeze crust 8-18″ below the surface (mid-pack) providing a uniform sliding surface.
Photo below is a wet slab avalanche on the West face of Lipps Ridge (2800ft).
Wet loose avalanches off of Tincan’s Southwest facing CFR ridge (2500ft)
Despite the grim facts concerning the wet snow stated above, at the high elevations it is snowing. Above 3,500′ new snow amounts during the past 48-hours are estimated between 2 and 3+ feet in the Turnagain Pass zone – up to twice that in other areas such as Portage and the Girdwood Valley. We have little information on how this new snow is adjusting, however what we do know is this is a significant load in a short period of time that warrants respect.
Storm snow instabilities will be in form of wind slab, cornices and loose snow sluffs. With ridgetop winds and precipitation decreasing overnight, these instabilities should gain strength rather quickly. This is due to the warm temperatures of the new snow along with no known preexisting weak layers in the snowpack at these upper most elevations.
Although we did not see any glide avalanche activity yesterday, the poor visibility and known existence of glide cracks between 1,500 and 3,500′, is enough evidence that these types of avalanches remain a concern. As with the travel advice for wet avalanches above, today is a day to avoid slopes steeper than 35 degrees and to steer clear of runout zones.
Yesterday’s weather was warm, wet and windy. During the past 48-hours Turnagain Pass has received 2.5 inches of water with greater amounts in the Girdwood and Portage Valleys. The rain/snow line hovered ~2000 feet yesterday and possibly up to 2500 feet in areas. Ridgetop temperatures have been ~30F and winds were predominantly from the East, averaging 30-40mph with gusts in the 60’s.
Overnight, temperatures have increased slightly and the rain/snow line looks to be just above 2000 feet with precipitation diminishing. Winds have also decreased and are remaining steady in the teens to 20’s mph along ridgetops from the East. Today, Tuesday, we are expecting .3-.5″ of rain below 2000-2500′ with 2-4″ of wet snow above. Ridgetop Easterly winds should remain in the 10-20mph range with temperatures near 30F.
The low-pressure system that moved through yesterday is headed inland today bringing a slight break in precipitation. However, warm temperatures are expected to continue over the next few days with periods of light rain and freezing rain. This should continue through Thursday, followed by another low-pressure system that could bring more precipitation closer to the weekend for Southcentral Alaska.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||36||0||1.4||19|
|Summit Lake (1400′)||35||0||0.2||4|
|Alyeska Mid (1700′)||37||0||1.3||12|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||31||E||18||47|
|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: 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.