CAIC

CAIC: Colorado Avalanche Information Center

BC Zone Observation Report

Saturday, January 16, 2016 at 12:00 AM
Front Range

Details

Date: 2016/01/16

Observer: Scott Toepfer Mike Cooperstein
Organization: Forecast Staff, Colorado Avalanche Information Center

Location

BC Zone: Front Range
Area Description: St. Marys

Weather

Ridgeline Wind Speed: 40+ mph
Ridgeline Wind Direction: W
Wind Loading: Intense
Sky Cover: Few
Weather Description: Winds at the lake were very strong. Hard to stand up during some gusts. Temperatures were mild which made the winds tolerable

Snowpack

Snowpack Description: Wind slab resting on facet layer on top of the same mix for 185 cm where we dug out snow pit. Large avalanche to the north of our pit had initiated as a wind slab resting on a 3 cm wind crust. We believe the slab quickly began to step deeper into old persistent weak layers, and eventually to the ground in some areas.

Snowpack Obsvervation #1

Cracking: None
Collapsing: None
Comments: Wind drifted slab of various thickness found here. Recent avalanche activity on similar slopes steep enough to slide give pause to any thoughts of riding steep terrain. Persistent weak layers near and below treeline mean any release could doze deeper.

Avalanches

Avalanche Description: Hard slab avalanche stepped to ground. East aspect, at 11,400 feet. Width estimated at 1,200 feet. Ran 650 vertical. Crown was blown back in, but would estimate some 36 to 48". Starting zone slope angle on the south end was 36 degrees, steeper as you went north.

Date

Location/Path

#

Elev

Asp

Type

Trig

SizeR

SizeD

View

2016/01/16 ^†

Other

1

TL

E

HS

U

R3

D2.5

Media

Images

<b>Figure 1:</b> Looking down at avalanche debris that ran onto the lake. St. Mary's glacier. Note the concentric "pressure wave" rings in the ice out from debris piles. 1.16.16 (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/wdhv9ix0udcnu1mwzk7y89d159cd?ixlib=php-3.1.0&s=2d39267fe72d2c7a7ed347f4fe897cdc','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 2:</b> Blocks of ice in the avalanche debris. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/n9y752mzrtkdduulesfum6hbbhcx?ixlib=php-3.1.0&s=419c4539729e738d694891691271989d','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 3:</b> Blocks of ice in the avalanche debris. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/0xixlgp6nyyk2ps8zhft1f8cmuqi?ixlib=php-3.1.0&s=a5e10b219b3746f96fd10009336e3e31','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 4:</b> Looking at the south flank of the avalanche. The black line shows where we could see an old crown. Much of the old slab boundary may have refilled during the strong wind drifting after the avalanche. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/z6qqevo55j3zgtqf337m65vbrn99?ixlib=php-3.1.0&s=ce15fb878ce38a2298c7b97b31c2167f','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 5:</b> Looking at the north flank of the avalanche. Black line shows where we could see the old crown. Deepest debris was at this end of the path, over 3 meters. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/h9ekhsuko6tvt6tru62m0727a3s7?ixlib=php-3.1.0&s=4a69dcd64dbb690c570002d405686fb7','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 6:</b> Looking at the toe of the avalanche debris at the south end of the slide. Debris surface smoothed from strong winds (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/1vfkm30pmt3um81j4nzeksnbj7qm?ixlib=php-3.1.0&s=463855f6f3407e2861aedd41c8bbb043','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 7:</b> Snowpit from far south end of path. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/xge2e8sofcfiinphc2rwnn3qh14f?ixlib=php-3.1.0&s=ec8ed3a94f8006a9deb063c6240f5174','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 9:</b> This lobe of debris calved into the lake when when the avalanche plunged into the lake & ice broke. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/lkiynp51mz87tqoaksh37dyw95uv?ixlib=php-3.1.0&s=ce70bf2ca58a61aa8930f8cb2bbad96b','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 10:</b> Looking north along the lake with debris lobes spread onto the ice. Deepest debris was on the north end. (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/mebesb61xjc28744dosbkx3fue4n?ixlib=php-3.1.0&s=8c304dce178b5712e0b3df7e15a1157c','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)

<b>Figure 11:</b> Lake ice block wrapped up in avalanche debris. CAIC forecaster for scale (<a href=javascript:void(0); onClick=win=window.open('https://caic-production.imgix.net/01whegdrwlblpxeu0bpoyaqrf3ci?ixlib=php-3.1.0&s=ebdf5fb5f658023c74f04161e3f54e68','caic_media','resizable=1,height=820,width=840,scrollbars=yes');win.focus();return false;>see full sized image</a>)