Hatcher Pass

uman-triggered avalanches occurred Tuesday March 12th.  These included several small and large storm slab avalanches, wind slabs, loose dry avalanches, two cornice triggered avalanches, and a wet loose avalanche.  The last natural avalanches observed occurred Tuesday March 12th, including several long running wet loose and loose dry avalanches on slopes steeper than 40 degrees. There were also several human-triggered and natural wind slab avalanches reported during the wind event on March 9 and 10 including a large wind slab human-triggered avalanche on a N aspect of Hatch Peak above $1000 run reported March 10.

Above: 2 larger (D1.5 to D2) slab avalanches, 3500′, estimated 6-12″ deep on NW aspect of Arkose (Punk Spines, due N of Stairstep), one of which looked to have sympathetically triggered another small slab avalanche below.

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Above: Several small (D1) soft storm slab avalanches, 4500′, 6-12 inches deep, on steep SW to W aspects of spines of Rae Wallace Chutes

Above: Cornice-triggered loose dry avalanche on SW aspect of Marmot at 4300′.

Above: Cornices have grown quite large along Marmot ridgeline and were sensitive to trigger on March 12.  This cornice was easily triggered resulting in a long running loose dry avalanche on the SW aspect of Marmot at 4300′. 

Above: Numerous long-running dry loose natural avalanches off steep (>40 degrees) S aspect of Microdot at 4600′.

Above: Long running loose dry avalanche on NE/E aspect of Skyscraper, 4500′, that ran from ridge into Eldorado Bowl about 700 ft.

Above: 100′ wide propagating human-triggered small (D1) wind slab avalanche on NE aspect of Lower Eldorado Bowl test slope at 3200′. 6-16″ deep soft slab. Observed on March 9th during wind event.

Above: Natural wind slab avalanches in NE aspect of cross-loaded Martin Mine Gully at 4000′ that is believed to have occurred overnight on March 8 during the wind event.

Above:Wind slab in W side of Hatcher Pass at 3900′ reported on March 9 during wind event.

Above: Natural wind slab that stepped down into buried persistent weak layers and failed at the ground in April Bowl at 4500′ on W aspect.  Reported on March 10 during the wind event. This path is a repeat offender and has avalanched many times this season.

East and Southeast winds gusting moderate to strong yesterday afternoon and overnight have formed fresh wind slabs 6-16″ thick in leeward and cross-loaded terrain, on predominantly W to N aspects. Southeast winds are expected to continue at 20-30 mph at ridgetops throughout today, which will continue to transport snow.  Human-triggered wind slab avalanches will be likely and natural wind slabs will be possible on W to N aspects, in mid and upper elevations. These avalanches could be large enough to bury, injure, or kill a person.

Pole tests will easily reveal stiffer snow sitting over weaker snow and will be a good indicator for the presence of wind slabs and slab thickness.

Above: Moderate to strong E to ESE winds Wednesday afternoon and night have built wind slabs 6″ to 16″ deep on leeward W to N aspects. 

It will be generally unlikely, but may be possible, to trigger an avalanche on deeper, buried persistent weak layers, SW to NE aspects, in mid to upper elevations, on slopes steeper than 35 degrees.  Small avalanches in isolated areas or extreme terrain. These avalanches may be up to 2′ thick and large enough to bury, injure, or kill a person.

13″ new snow and moderate to strong winds this week have built large cornices that have proven sensitive to trigger.  Give cornices a wide berth as they can break back much further back then they appear and cornices can trigger larger avalanches below.

Above: New snow and moderate to strong winds over the last week have built large cornices.  Pictured here are large cornices above Rae Wallace Chutes.