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Strange weather makes strange avalanches

Hermit Lake caretaker, Pat and I went to make some field observations in Tuckerman today despite the ludicrously cold temperature and wind. Our safest choice for travel was higher on the right side of the Bowl since there was still some active wind loading going on and would allow views of Right Gully and Sluice while hopefully allowing us to get a sense of the sensitivity of our current wind slab issues. We picked our way among the rocks, trying to avoid walking on the rock-hard melt/freeze crust while simultaneously staying out of the runouts of Right and Sluice. As I struggled to get decent photos, Pat pointed out the blocky debris to our left in the rocks. A sharp feature in the snow,  barely visible between short periods of whiteout yesterday morning, emerged from the murky gray whiteout. This feature had caught my eye yesterday morning but was in such an odd location for a crown, in a spot where we frequently see sharp wind lines, that I thought little more about it. From our vantage point and with the debris below, it was pretty clearly a small avalanche crown not running out of Sluice but starting, more than likely sympathetically with the larger avalanche that tore through the Ravine Thursday night. I did a really hasty crown profile due to really harsh weather and found the 40m long crown, 35-40cm thick hard slab (P) had a soft layer (F) beneath from the 8 inches we received earlier in the week. All this was on top of the melt-freeze crust. Though much of Tuckerman and Huntington is scoured down to this boilerplate crust, lots of slabs similar but larger than this one in the photos below are lurking around in the Ravines and resting on the weak 4% density snow deposited in low winds. On my way down I walked along some drifts which formed soft slabs at the base of Lunch Rocks, testing steeper pockets and getting lots of short but insistent cracking. As I entered flat terrain of the floor, just out of the runouts, walking across a long 2 foot thick drift a loud whoompf jump started my heart and was a good reminder that our snowpack may be lean but it is really dynamic. Near crust faceting may be further weakening this weak layer on the melt/freeze crust so stay heads up out there and keep a close eye on the coming storm on Monday. More load on this weak layer will likely result in more avalanche activity.

20160122_LR crown drawn in

This photo (from Jan 22, 2016) shows the very rough location of the crown from Friday’s avalanche cycle in the Lip and Center Bowl and the approximate location of the crown in the accompanying photos below. The slope angle was in the low to mid 30’s and beneath the rollover below the bowl like feature under Sluice ice and to the right of the slight rollover marking the lookers right edge of Chicken Rock gully. This is often the point of access for people entering Chicken Rock gully from Right Gully since it is generally flat, low angle and avoids the rollover above.

upper Lunch Rocks crown

Left side or inverted V shaped crown with the top right of the crown visible in the distance.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Elevation relative to Lip and Chicken Rock

The rocks in the background mark the top of the feature we call Chicken Rock Gully. The crown starts near the upper right corner of the photo though you can’t pick it out in the photo. It was -20F or so and blowing like heck (50mph on summit 35 mph+ in the Bowl) so operating the phone was problematic.

 

Debris in Lunch Rocks.

Looking down from a point 200′ or so feet below the crown. As you can see the debris reached and flowed over and around the Lunch Rocks rescue cache. The cache is located to the left and just out of frame of the large boulders below.

-Frank