Avalanche Activity

2/17-18-  A Significant avalanche cycle occurred during this time period.  Most of the activity failed on deep persistent weak layers.  These were the 1/24 facet-crust combo and the November facets.  Numerous hard slab avalanches were observed that failed near the ground.

Deep hard slab activity included: Billy Mitchell, Happiness, 40.5 Mile Peak, NE Crudbusters Multiple spots around the Tonsina Glacier, West side of Iguana backs (really wrong place), Multiple spots in the Tsaina valley, Girl Mountain, Cracked Ice, Python, Buttress west of Nicks (this is has slid multiple times this year), North Oddessey shoulder.  This is only a portion of the activity that occured.  

Most of the activity occured around 4000′, although there were outliers at upper elevations.

Billy Mitchell

Iguana Backs (Really Wrong Place)

Girls

Python

Cracked Ice

Tonsina Glacier

North Oddessey Shoulder

2/17 – Keystone Canyon was reported to have many size 1-2 loose avalanches on the steep canyon walls.  Crowns with depths of 10-15″ have been reported as well on the ice climbs Simple twist, Bridal Veil and Green Steps.  Photo approach to Simple Twist

2/15- A large deep persistent avalanche occurred on “Back It In” near Mt Dimond.  The trigger is unknown, but was most likely triggered remotely by a helicopter landing on a recon mission.  It appears that a cornice fall triggered a shallow slab over rocks which then stepped down creating a deep slab ~500 feet wide that entrained the entire snowpack.  Several other deep slabs failed sympathetically below.

2/13 – Meteorite ramp was reported to have released full path failing at the bedrock.

2/9 & 2/10- Numerous natural avalanches occurred during this time period.  

Mt tiekel (50 mile) and 38 mile ran naturally, with 38 mile depositing a small amount of debris on the road.  

 The entire Python Buttress failed naturally close to the ground with a crown line approximately 1/4 mile in length. Numerous avalanches in the gully to the east occured as well.  Debris from both areas extended ~200 meters across flat terrain.  

 Gully 2 and Nicks had significant slides run into their fans.

 Snowslide Gulch ran naturally and hit the road.  

DOT mitigation efforts produced activity at Three Pigs and Snowslide Gulch.

Natural activity was more extensive than noted.  Snowfall continued after the event refilling crowns and preventing a good look at the extent of natural activity.

1/30-Several natural persistent slab avalanches were observed in the intermountain and continental zone.  

• Remote snowmachine triggered avalanche on Little Girls/ SE aspect/~3500′.   Member of group reported that 2 members of a larger party were waiting on the lower angle ridges (bro bowl up route) below the slide pictured waiting for the rest of a larger group.  Rider 2 went to play on a small hill nearby when rider 1 felt a large collapse and the slides pictured came down.  The rest of the group gathered up and about 5 minutes after the remote trigger felt an earthshaking collapse that had alders swaying and group reported the feeling of dropping/settling a vertical foot.  A noise that was described as a bomb quickly followed.  The group left the area immediately and did not observe any further avalanche activity caused by the collapse.  Other collapses were noted later in the day.
• Natural avalanche on the Little Matterhorn buttress/ North/ ~3500′.  This avalanches’ width implies that it was more than a wind slab avalanche and failed on a persistent weak layer.  The interesting thing was how wide this avalanche was, and that the depth was much shallower than other persistent slabs that have been noted.  The takeaway point is that our area has a lot of spatial variability, meaning that dangerous facets snow may be buried deep in some areas making it very difficult to affect.  And in other areas weak faceted snow from November exists close to the surface in some locations, making it easier to affect.  Use caution in steep areas with thin snowpack.
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• Natural D3 persistent slab avalanche Area 51/ North, east, and west aspects/ ~3500
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• Natural D3 persistent slab avalanche Pt 6153 just north of Averys/ ~5500′

Natural D3 Persistent slab avalanche/ Shovel/ northeast aspect/~5000′.

South aspect hogback ridge/~3000′

Snoopys/East aspect/~4000′

1/29- Observed numerous D2 avalanches on Billy Mitchell (cry babies area) and one D3 on Happiness.  These were all northerly aspects.  On Billy, slides originated between 3-4000 feet and on Happiness ~5000′.

1/28- During brief break in the clouds, observed a Natural D3 avalanche on Catchers Mitt.  It is likely this slide failed on a persistent weak layer, as the crown was deep (3-4) feet and ran a considerable distance.

1/22-1/24- A D3 natural avalanche was observed on 1/22 in snow slide gulch that ran to just below the summer trail.  

On 1/26 2-D3 naturals were seen on the east face of Mt Tiekel (beyond forecast zone) that ran half way through their aprons.  These likely occured between the 1/22-1/24 time period.

Clouds prevented observation of where these slides originated

1/22-  Clouds made observing avalanche activity difficult, although numerous large wet loose slides were observed on south aspects of Town Mountain in the Port of Valdez.

1/13- Multiple large natural avalanches were noted following the snowfall on 1/13.  Most were near high elevation ridge lines, although mid elevation storm slabs were noted on north aspect of Catchers Mitt and south aspect of Mile high.  Other avalanche not shown in photos include Goodwills north aspect and Oddeyssey north aspect.

1/1-1/4-  The new years day wind event created an avalanche cycle that was difficult to document due to crowns being rapidly reloaded by 80 mph winds.  Below are photos of a couple very large slides that were still visible in the Hippie ridge area.  Naturals were also noted on Three Pigs, 40.5 Mile, Crudbusters, Python Buttress.

12/29-  Multiple natural wet loose D1-D2’s were observed in the Port of Valdez with no step downs noted.

12/23- Berlin Wall north face ~5000′ HS-N-R3-D2-O.  It is possible this occurred on 12/21, although it was not observed until 12/24.

12/21- Numerous natural avalanches observed all along the north side of Thompson Pass, as a result of strong NE wind event along with a couple inches of new snow and rising temperatures.  Observed naturals on all aspects except windward slopes with crowns originating from 1000 feet to 5500 feet in elevation.  Most of these were hard slab avalanches.  Crown depths were difficult to discern due to reloading, although some crowns looked to be up to 2 meters in depth.

12/19- D 2.5 natural avalanches were observed on the north facing buttress west of Gully 1 and Schoolbus.  

12/14-  Several natural avalanches were observed although poor visibility prevented a full view of the action.  The most notable natural was observed in Nicks Happy Valley on a NW aspect ~4000′.  Crown depth was not visible.  Debris ran down the valley and piled up at the typical snowmachine pickup.

12/8- Large remote trigger/ sympathetic avalanche event occurred 12/8 with avalanches extending from Gully 1 to Nicks.  Avalanches were soft slabs that ranged in size from D1-D3.  Over 10 separate avalanches were counted with crown depths averaging 2-3′.  One avalanche had a crown length of half a mile while another was triggered over a mile away from the point of collapse.  See observation section for full report and more photos.

12/7- Only a few natural avalanches were noted during the last storm.  It is likely there were more during the storm, but crowns may have been filled in by subsequent wind and snow.

D2’s on Town mountain was observed ~3000′

A couple of D2’s were noted in N. Oddessey gully and Big Oddessey.

D2 on 40.5 mile peak ~5500′.

12/2-12/3- Several natural D2 avalanches were noted on south aspects of Three pigs, Hippie Ridge and Averys.  These windslab avalanches originated between 4000-5500 feet elevation.