Early Season Avalanche Mitigation 2012-2013 Alyeska Ski Patrol

Published on Jan 3, 2013

Happy New Year from the Patrol and Snow Safety Departments

A message to all Alyeska skiers and riders:

This year our October, November, and early December weather pattern left us with a blanket of sugary, faceted snow on the entire mountain. In addition, several wind events during this time created hard slab conditions on top of the sugary, faceted snow in many of our avalanche starting zones. On December 24, a large change in the weather pattern began a stream of moisture, wind, and snowy weather that has left us with over 190" of snow and 18" of snow-water equivalent. This significant cycle of weather has created avalanche conditions not seen by many of the old-timers around here for 20+ years. In light of this, it has been very challenging to keep up with avalanche mitigation measures so we can safely set up the mountain for the public.

Many of you have likely seen the myriad of recent avalanche warnings and High Danger levels posted by the local avalanche center. We wanted to share a few anecdotes and stories with those of you familiar with the terrain here at Alyeska to illustrate the unique nature of the problems we are dealing with this year.

On Christmas Day mid-morning while we were assessing the regular area, we discovered a natural avalanche on the North Face. This slide had a crown of approximately 5-7 feet deep and propagated from the area near Lolo's over past Pandora's and Ragdoll. This slide ran 90% of the climax release for this path and deposited significant debris on the kettle ponds under the tram at the base of Last Chance Cliffs. Two days later, on the afternoon of December 27th, another natural avalanche occurred in the exact same area. This 2nd natural slide had four different pockets in the Banjo area break out 4-5 feet deep and the debris ran down past the North Star Gate in the lower West Line area, approximately 65% of the climax release for this path.

On two different occasions within 3 days of each other, the entire Gail's Gulley and Prospector areas released 3-5 feet deep and deposited debris down past the bottom of Main Street, into Champagne, and down to the top of Alpine Gulley. Debris depth at the bottom of Main Street was 8-10 feet deep on both occasions.

A unique event for all of you Silvertip Face lovers occurred one morning a few days after Christmas during an artillery mission. The Saddle Center shot point (located at the boot pack for the Headwall hike) released a Class 3 avalanche 4-6 feet deep and ran down onto Silvertip flats. Although the toe of the debris did not quite reach the Silvertip Nose, the rumble of that slide sympathetically triggered the entirety of Silvertip Face 4-6 feet deep and ran down to the Ego Flats area. Sympathetic triggers occur when an avalanche descends, especially in very unstable conditions, and triggers avalanches on nearby slopes.

Another area to note that normally isn't a problem when we have our maritime snowpack is the lower South Face above the Top of Chair 4 area. On one occasion, a patroller remotely triggered an avalanche above the top of Chair 4. This patroller checked their speed on the flats above the rollover of this path and triggered a slide 100 feet away that was 3 feet deep, broke to the ground, and ran down to the top of the Chair 4 area. On numerous other occasions, explosives mitigation measures on the Lower South Face sent avalanches 3-5 feet deep down across the Hammel Highway, past Radiation Grove and the Runway Cliffs and onto the Runway.

We are sure many of you longtime Alyeska lovers can extrapolate these results to other areas. We are seeing large, unusual avalanche problems such as Brown Shorts, White Shorts, Kitchen Wall, Ashtray, Bird Hill, Wicks Knoll, Gun Mount, Main Street, Gear Jammer etc. etc. A majority of the 160+ avalanches (Class II or larger) we have seen inside the ski area boundary this year have been in old snow layers and many have been natural triggers.

Amidst all this, the artillery missions have of course been sending large amounts of debris time and time again down from the Glacier Bowl, Headwall, and Shadows.

As a team, this means we have, and will continue, to approach with extreme caution, with the utmost suspicion of the stability of the snowpack. To our pass holders, many of whom we know by name and recognize by your outfits, we realize these times can seem agonizingly slow for a ski town population craving their share of powder snow. For what it is worth, please know we are working as hard as we possibly can within the limits of the snowpack and acceptable risk to ourselves. Skier compaction from our loyal powder hounds is one of our favorite tools for snowpack stabilization and we will let you all have it just as soon as we can. We appreciate you all hanging in there with us this season.

All the best,

Alyeska Patrol and Snow Safety
January 2013