Strong Easterly winds have been changing the surface conditions of our forecast zone over the last 4 days creating hard wind slabs on leeward features. Many ridgelines have been exposed down to rocks, dirt and old crusts. Observations yesterday found hard supportable wind slabs as low as 1600’ on Eddies. These slabs averaged around 5” thick and were failing in hand pits on old weak snow. Any wind slabs today will be hard and supportable (to a skiers weight) and may lure a skier well onto a slope before it fails. Be suspect of unsupported slopes steeper than 30 degrees that have a fat, smooth, pillow-type shape to them. Listen for that hollow, drum-like sound below your skis or use a pole to probe for that hard snow over weak set up. These slabs could be as thick as 1-2’ deep in upper elevations and have the potential for initiating a much larger and more dangerous deep slab avalanche. More on this below.
A handpit that failed on isolation on weak snow below, near surface facets and buried surface hoar. Yesterday at Eddies at 1900′ on a West aspect.
Many windward slopes have eroded down to rocks, dirt, and crusts, but cross loading is still possible around gullies and terrain features on windward slopes. Photo of the SE face of Seattle Rigdge near Pyramid Peak.
The recipe for deep slab avalanches has been found in the upper elevations of our forecast zone, above 3000’ on slopes that did not avalanche during the early December storm cycle. The snowpack ranges from 3-5+’ thick and is sitting on weak basal facets. Observations over the last few weeks indicate this poor structure is widespread across our region in the alpine elevations. This is a high consequence avalanche problem that is impossible to outsmart.
When dealing with a deep slab avalanche problem, keep in mind:
This Deep Slab avalanche on the NW face of Pastoral was remotely triggered from below on Dec.20 by a party of two skiers who were able to run out of the way of the debris. This is an example of the potential that still lingers in upper elevations, above 3000′ on slopes that haven’t avalanched. For more details on the snowpack structure click HERE and for a description of what happened click HERE.
Yesterday Strong Easterly winds decreased to Moderate, averaging 15mph with gusts in the 30’s. Temperatures at lower elevations were above freezing, mid to low 30F’s at 1000′ and low 40F’s at sea level. Temperatures at ridge tops remained in the low 20F’s. An inch of new snow fell yesterday.
Today a trace of snow is possible and winds are expected to be East, 5-20mph. Skies could range from overcast to partly sunny. Temperatures in the lower elevations should start cooling into the 20F’s today.
High pressure is expected to settle over mainland Alaska this week with several lows tracking South of the Gulf of Alaska. This should allow for some clear skies and cooler temperatures. Northerly gap winds are possible this week as well as an occasional snow shower.
*Center Ridge SNOTEL is reporting erroneous temperature data. See Turnagain Pass DOT weather station for accurate temperature at 1000′
**A max gust of 72mph occured at 7am on 12/24/17 at Sunburst Wx Staion before winds decreased and gusts were averaging in the 30’s mph most of the day.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||*34||1||0.1||30|
|Summit Lake (1400′)||31||1||0.1||11|
|Alyeska Mid (1700′)||31||2||0.2||27|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||26||ESE||15||48|
|04/19/21||Turnagain||Avalanche: Triangle, Seattle creek||Will Morrison|
|04/18/21||Turnagain||Avalanche: Turnagain Pass Road Obs||Andy Moderow|
|04/18/21||Turnagain||Observation: Seattle Ridge, approximately 300 yards south of the up track||Brent Byrne|
|04/17/21||Turnagain||Avalanche: Road obs||Johnston-Bloom / Moderow Forecaster|
|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|
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.