17-18
Cornices have grown very large and are severely overhung. They sometimes break much further back than anticipated and can take you for a nasty, sometimes fatal ride. Plus they are excellent at triggering avalanches in the wind pillows below them. This photo was taken on the ridge north of Bridger Bowl. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Wed Feb 21, 2018GNFAC Avalanche Advisory for Thu Feb 22, 2018GNFAC Avalanche Forecast for Fri Feb 23, 2018GNFAC Avalanche Advisory for Sat Feb 24, 2018GNFAC Avalanche Advisory for Sun Feb 25, 2018GNFAC Avalanche Advisory for Mon Feb 26, 2018GNFAC Avalanche Advisory for Tue Feb 27, 2018
A skier observed large cornices north of the Bridger Bowl boundary, despite the east wind several days ago eroding some snow at higher elevations. Always give these beasts a wide berth, and remember that they can break farther back than expected. Photo: H. Coppolillo
GNFAC Avalanche Forecast for Tue Feb 20, 2018
Snowpack and Avalanche Discussion
<p>Although winds have calmed around Cooke City, there was 3’ of new snow over the weekend that got blown around on all aspects and elevations. This snow measured 3” of <a href="http://www.or.nrcs.usda.gov/snow/about/swe.html">snow water equivalent</a> and even on slopes untouched by the wind, avalanches are still possible. Wind drifts of snow can be triggered by a skier, sledder or falling cornice. Yesterday a skier saw a 4-6’ deep avalanche on a wind-loaded slope on Mt. Republic (<strong><a href="https://www.mtavalanche.com/images/18/natural-avalanche-mt-republic">ph…;) that likely broke during the storm. It’s been 24-hours without snowfall, winds are decreasing, and the danger is dropping as the snowpack adjusts to this weekend’s load. For today, the avalanche danger is rated <strong>MODERATE</strong> on all slopes.</p>
<p>Yesterday, while I was warm and toasty in the office, Eric and his partner skied up Hyalite into Maid of the Mist and froze. They found the snowpack to be generally stable <u>except</u> on wind-loaded slopes. They ran into two others who triggered a slide when they unexpectedly broke off a large cornice mere inches from their feet as they traversed the ridge. The cornice triggered a slide on the wind-loaded slope below which erased part of their up-track (<strong><a href="https://www.mtavalanche.com/images/18/skier-triggered-cornice-hyalite">…;). This story illustrates the avalanche concern from the Bridger Range, to Big Sky and West Yellowstone. Two feet of snow since Friday was blown into drifts and fed cornices. On Sunday, Alex and I saw super-sized overhangs on Buck Ridge (<strong><a href="https://www.mtavalanche.com/images/18/cornices-second-yellowmule">photo…;), and snow rangers found an avalanche on a heavily wind-loaded slope in Teepee Basin (<strong><a href="https://www.mtavalanche.com/images/18/avalanche-wind-loaded-slope-tepee…;). Winds since Friday were all over the compass, so be wary of slopes under cornices or in gullies where drifts are most likely to be found. Alex warned us about wind-loading during Saturday’s trip to Fairy Lake (<strong><a href="https://youtu.be/qUooGmpF9Ss">video</a></strong>),which mirrored Eric’s visit on Friday to Cabin Creek (<strong><a href="https://youtu.be/0j-w-w85tDM">video</a></strong>). For today, slopes that are wind-loaded have a <strong>MODERATE</strong> avalanche danger while all others have a <strong>LOW</strong> danger.</p>
<p>Cornices break easily and have killed many unsuspecting people, some friends of mine. They fool us into thinking we are on solid ground when, in fact, we are standing on a thick diving board of snow. Give cornices a wide berth (<a href="https://www.mtavalanche.com/images/18/cornice-illustration">illustratio…;).</p>
<p>If you get out and have any avalanche or snowpack observations to share, drop a line via our <a href="https://www.mtavalanche.com/node/add/snow_observation">website</a>, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Upcoming Avalanche Education and Events
BOZEMAN
Feb. 28th, Know Before You Go avalanche awareness, 7:00 p.m. @ Procrastinator Theater, MSU
March 2nd and 3rd, SheJumps Companion Rescue Clinic, Info and Register HERE
Cornices break easily and have killed many unsuspecting people. They fool us into thinking we are on solid ground when, in fact, we are standing on a thick diving board of snow. Give cornices a wide berth.
This natural avalanche was observed on an east aspect around 9000' on Mt. Republic. Crown estimated at 4-6' deep, on a rocky wind-loaded convex rollover. 3" of SWE and heavy winds have drifted wind slabs at various elevations. Photo: B. Fredlund
Skiers up Hyalite triggered this cornice on Mt. Bole as they traversed along the ridgeline. The cornice triggered a small slab avalanche that took out the skiers skin track. Cornices are under a lot of stress from this week's snow and wind and should be given a wide distance along ridges. Photo GNFAC