18-19
Weather and Avalanche Log for Wed Nov 28, 2018
Cracking and collapsing above Hebgen Lake.
GNFAC Avalanche Forecast for Wed Nov 28, 2018
<p>Since Thanksgiving, over a foot of snow (1+” <strong><a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2…;) fell with strong west to southwest winds. Folks saw a few natural avalanches up Hyalite (<strong><a href="https://www.mtavalanche.com/images/18/new-snow-avalanche-near-mt-blackm…;), and in the Bridger Range (<strong><a href="https://www.mtavalanche.com/node/19122">report</a></strong>), while skiers in Bear Basin in the northern Madison Range triggered a wind slab that they captured on <strong><a href="https://youtu.be/q1aqN4N6Gww">video</a></strong>. Avalanches were not widespread and were confined to the new snow. This matches our findings from the field which Alex describes in a <a href="https://youtu.be/CF0zmpxFeM8"><strong>video </strong>from Middle Basin</a> (north of Big Sky) as well as <strong><a href="https://www.mtavalanche.com/snowpits">snowpit profiles</a></strong> recently dug throughout our forecast area.</p>
<p>The underlying snowpack is generally strong and our primary concern is with today’s new snow. Snow and wind will create thick wind-drifts near the ridgelines which will be easily triggered. Recent avalanches or cracking (<strong><a href="https://www.mtavalanche.com/images/18/thin-slabs-cracking">photo</a></s…;) of this new snow are signs of a rising avalanche danger. Stay out of avalanche terrain if you witness these warnings. </p>
<p>The snowpack in the Lionhead area outside West Yellowstone is shallow, weak and unstable. Alex was there on Monday and found a 2’ deep snowpack that consisted of sugary grains of facets capped by 6” of new snow (<strong><a href="https://www.mtavalanche.com/images/18/shallow-weak-snowpack-lionhead">p…;). His <strong><a href="https://youtu.be/hl5lygIF7s4">video</a> </strong>shows the crumbly nature of the facets and their inability to support much new snow. With today’s snowfall and wind a skier or rider can trigger an avalanche, especially at the ridgelines where wind-drifts will be thick and unstable.</p>
<p>New this season, we added hyperlinks to the <u><strong><a href="https://www.mtavalanche.com/weather/wx-avalanche-log">Weather and Avalanche Log</a></strong></u> and a new Menu item <<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">Avalanches and SnowPits</a></strong></u>> with information on avalanche activity and incidents.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
TONIGHT! November 29, 30 and Dec 1, 2or 8, Intro to Avalanche w/ Field Day, more info here
A skier triggered this small wind slab along a wind loaded ridge in Hyalite. Although small, it's an obvious clue wind loaded slopes are unstable. Even small slides can have severe consequences if triggered in steep-exposed terrain or on slopes with terrain traps such as gullies, trees or rock bands. Photo: G. Antonioli
Slopes loaded by west-southwest winds are the main avalanche concern. Cornices and natural avalanches are bull's eye information slopes are wind loaded and unstable. Watch for and carefully assess all slopes with wind drifted snow. This photo was taken in the northern Madison Range. Photo B VandenBos
Skier triggered new snow avalanche
From e-mail: "Today while skiing Bat Ears Couloir in Bear Basin we encountered fast moving 12" deep wind loaded sluff however, it didn't step down."
Second e-mail: "Upon entering the couloir I performed a ski cut and released an 8 inch deep slab that was about 12 feet wide that ran about 700 vertical. Then we skied the slide path down and safely returned into beehive by exiting down bear basin. "
Yesterday at Lionhead Ridge near West Yellowstone we found a shallow and weak snowpack. A foot of weak, sugary snow on the ground will create unstable conditions where it is buried by thick drifts of snow, and when the area gets more snow later this week. Photo: GNFAC
Forecast link: GNFAC Avalanche Forecast for Wed Nov 28, 2018