20-21

<p>We issued an Avalanche Warning for the Bridger, northern Madison and northern Gallatin Ranges. The snow is piling up and adding weight to a weak snowpack. Weather stations are showing 20-30” of snow since early Monday measuring 2.2” of&nbsp; <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</u></a>-SWE in the Bridger Range and 1.4” SWE in Big Sky and Hyalite (1” SWE in last 24 hours). Reports from ski patrols indicate high snowfall rates. Big Sky Ski Patrol measured 3” of snow falling in an hour after they closed, something the weather stations did not pick up on. I’m nervous because even though the snowfall/SWE numbers may not seem like much, reports from the field indicate otherwise. We have a weak snowpack with sugary facets near the ground. On Sunday a splitboarder died from injuries he sustained in an <a href="https://www.mtavalanche.com/accident/21/02/16"><strong><u>avalanche in Beehive Basin</u></strong></a>. Last week two snowmobilers got very lucky when they were not caught after triggering a large avalanche in <a href="https://www.mtavalanche.com/node/24219"><strong><u>Portal Creek</u></strong></a>, and skiers saw large avalanches on <a href="https://www.mtavalanche.com/node/24299"><strong><u>Divide Peak in Hyalite</u></strong></a>.&nbsp;</p>

<p>A big snowstorm makes big avalanches. Our mountains have a weak snow structure and recent avalanche activity means we should expect more avalanches today. The danger is rated HIGH on all slopes. Stay away from all avalanche terrain including runout zones.</p>

<p>The southern Madison and southern Gallatin Ranges got another 4” of snow yesterday bringing their storm total to 15”, measured as 1.2” of SWE. The snowpack structure is weak with sugary facets at the bottom of the snowpack that can avalanche. The new snow will also be unstable at the interface of the new/old snow a foot under the surface. Wind-loading from west-northwest wind will further increase the load at the ridgelines and starting zones. Ian was in Teepee Basin last week and saw avalanches (<a href="https://youtu.be/Zyj4LwxoEaU"><strong><u>video</u></strong></a&gt;), and a rider was caught in a <a href="https://www.mtavalanche.com/node/24253"><strong><u>slide in Cabin Creek</u></strong></a> on Saturday. All this snowfall is creating dangerous avalanche conditions. Triggering slides, potentially large and deadly ones, is likely. Today is a day to stay out of avalanche terrain because the danger is rated CONSIDERABLE on all slopes.</p>

<p>The mountains around Cooke City and West Yellowstone have not had a big snowstorm, but they are getting incremental loading and wind. In the last 3 days 9” of snow has fallen measuring .6-.7” of SWE. Winds was strong from the west to northwest Monday and Tuesday, but is dying down today. The major concern are wind-loaded slopes and slopes that have facets near the ground. Facets are found on most slopes in Lionhead and in thin areas (less than 4 feet deep) around Cooke City.&nbsp; Recent avalanche activity, even on small slopes, is a sign of instability (<a href="https://youtu.be/JaB-L-41KvA"><strong><u>video</u></strong></a&gt;). Dig, test and be cautious traveling in avalanche terrain, especially where the snowpack is thin and wind-loaded which I explain in this <a href="https://youtu.be/7zv-hg9gzOI"><strong><u>video</u></strong></a&gt; from the weekend. For today the avalanche danger is rated MODERATE on all slopes.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>In the last 48 hours, the Bridger Range received 20” of snow equal to 1.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</a>-SWE. New and wind-drifted snow are likely to avalanche in steep terrain today under the weight of human triggers and avalanches breaking deeper into the snowpack on sugary facets near the ground are a growing concern as the weight of the new snow adds up. On Sunday,<em> before</em> the new snow fell, Alex and I choose to stay off steep terrain due to continued concerns about the weak structure of the snowpack (<a href="https://www.youtube.com/watch?v=DW0RqKtnxUw&amp;list=PLXu5151nmAvQDzKmH…;). Today, obvious signs of instability such as fresh avalanches, collapsing or whumphing, and shooting cracks will be more likely. Heed these warning signs.</p>

<p>Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential due to dangerous avalanche conditions. Human-triggered avalanches are likely and the danger is rated CONSIDERABLE.</p>

<p>The Lionhead area and the Madison and Gallatin Ranges received 8-14” of new snow in the last 48 hours equal to 0.5-0.9” of SWE. Sunday’s fatal avalanche accident in Beehive Basin is a tragic reminder that slides breaking deep within snowpack on weak facets near the ground are a very real possibility. Preliminary <a href="https://www.mtavalanche.com/index.php/node/24274"><strong>information and photos</strong></a> are available on the website and we published a <a href="https://www.youtube.com/watch?v=_gLB_fAZsb8&amp;lc=UgyAxJPwsRH7phS4Pyt4… </strong></a>explaining the events after our visit to the accident site yesterday.</p>

<p>Ongoing snowfall and wind-transported snow are adding weight to a structure near or reaching its failing point. Yesterday, skiers in the Divide Cirque saw two enormous avalanches that broke an estimated 1200-1500’ across and up to 6’ deep in wind-loaded, high elevation terrain (<a href="https://mtavalanche.com/node/24299"><strong>details and photos</strong></a>). Skiers near Hebgen Lake felt the snow in shallower, low elevation terrain whumphing as they toured toward their destination (<a href="https://mtavalanche.com/node/24300"><strong>details</strong></a&gt;). This evidence along with avalanches at <a href="https://www.mtavalanche.com/images/21/lionhead-snowmobile-triggered-sli…;, <a href="https://www.mtavalanche.com/images/21/remotely-triggered-slide-portal-1… Creek</strong></a>, and <a href="https://www.mtavalanche.com/node/24253"><strong>Cabin Creek</strong></a> within the last week tell us what we need to know (<a href="https://www.youtube.com/watch?v=Zyj4LwxoEaU"><strong>video from Teepee Basin</strong></a><strong><u>)</u></strong>. Avoid steep, wind-loaded terrain today and utilize a conservative travel plan along with careful snowpack evaluation. Human-triggered avalanches are likely in wind-loaded terrain and the danger is rated CONSIDERABLE. Avalanches are possible on non-wind-loaded slopes and the danger is MODERATE.</p>

<p>The mountains around Cooke City received 7” of snow in the last two days equal to 0.5” SWE. The snow is starting to add up and riders and skiers should stay off of steep slopes if they observe signs of instability such as recent avalanches, cracking, and collapsing (<strong><a href="https://www.youtube.com/watch?v=JaB-L-41KvA">Small Avalanches are a Warning video</a></strong>). When Doug visited Cooke City last weekend he noted two areas of particular concern, the terrain where slabs of wind-drifted snow are loading slopes and terrain with a shallower and weaker snowpack&nbsp;(<a href="https://www.youtube.com/watch?v=7zv-hg9gzOI&amp;list=PLXu5151nmAvQDzKmH…;). Numerous avalanches occurred within the last week on steep slopes where one or both of these factors existed (<strong><a href="https://mtavalanche.com/images/21/natural-avalanche-west-side-woody-rid… photo West Woody Ridge</a></strong>, <a href="https://www.mtavalanche.com/images/21/large-avalanche-mt-abundance"><st… Abundance</strong></a>, <a href="https://www.mtavalanche.com/images/21/natural-avalanche-town-hill-cooke… Hill</strong></a>, <a href="https://www.mtavalanche.com/images/21/woody-ridge-avalanche-wide"><stro… Ridge</strong></a>, <a href="https://www.mtavalanche.com/images/21/natural-avalanches-near-zimmer"><… Zimmer</strong></a>, <a href="https://www.mtavalanche.com/node/24248"><strong>Hayden Creek drainage</strong></a><strong><u>)</u></strong>. Today, evaluate the snow and terrain carefully avoiding these features of concern. Human-triggered avalanches are possible and the danger is MODERATE.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>