21-22

<p>Today is a serious day in the northern ranges. Snowpack stability is changing for the worse, and fast. It has been 72 hours without freezing temperatures between 8-9,000 feet in the Bridger Range, Hyalite and Big Sky area. Mountain temperatures are expected to rise into the high 40s with sun and minimal wind, a trifecta of ingredients for wet avalanches. Conditions will worsen throughout the day. Stay away from avalanche terrain and avalanche runout zones that are getting sun or are wet. Wet loose and wet slab avalanches are likely. Avoidance is the key to staying safe. Digging a snowpit is not required, just situational awareness.&nbsp;</p>

<p>If you can magically port yourself onto cooler, upper elevation, north facing (shaded) slopes, then you’ll need to contend with a few wind drifts that could break, but this concern is secondary (<a href="https://www.mtavalanche.com/avalanche-activity"><strong><u>avalanche activity list</u></strong></a>). First you’ll have to navigate lower elevation, wet avalanche territory, our primary concern. Avalanche danger will rise from MODERATE to CONSIDERABLE on all slopes that are getting sunshine.</p>

<p>The southern mountains from Big Sky to West Yellowstone have temperatures that are below freezing by a couple degrees. Warm temperatures and some sunshine will create wet avalanches, but these will likely be loose slides on the surface instead of deeper slabs. Wet snowpacks are dynamic and can surprise us, so be extra cautious today. Faceted and weak snow are found in the top 6-18” of the snowpack. In a few areas wind drifts have added enough weight to create instability. Ian and I had a <a href="https://www.mtavalanche.com/node/26053"><u>whumpf yesterday</u></a> in a snowpack that had a thick wind slab over faceted snow, a recipe found throughout our southern ranges. If the snow is dry, dig to test the weak snow. If the surface is wet, stay out of avalanche terrain. For today avalanches are possible and the danger is rated MODERATE on all slopes, wet or dry.</p>

<p>In the mountains around Cooke City there are two issues to be concerned with: a weak layer of faceted snow buried 2 feet deep, and wet loose avalanches on steep slopes that are getting sun.&nbsp; A skier triggered and was caught in an avalanche on Tuesday near Goose Creek on this weak layer. He was luckily unharmed (<a href="https://www.mtavalanche.com/node/26049"><strong><u>photos and details</u></strong></a>). This is the most recent slide in a list of avalanche activity (<a href="https://www.mtavalanche.com/avalanche-activity"><strong><u>avalanche activity list</u></strong></a>, <a href="https://www.youtube.com/watch?v=SxPaEcKATts&amp;list=PLXu5151nmAvT1nrM2…;). Yesterday a skier noted many wet, loose avalanches in steep terrain on Mt Abiathar in YNP (<a href="https://www.mtavalanche.com/node/26056"><strong><u>details</u></strong>…;). I expect to see similar wet avalanches around Cooke City today. Do not get into steep terrain if you see recent slides, or find instability. It remains possible to trigger avalanches and the danger is rated MODERATE.&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>As we noted in Beehive Basin yesterday, a mixed bag of weather including strong winds, light snow, light rain and warm temperatures, brings a mixed bag of avalanche problems to the mountains around Bozeman, Big Sky and West Yellowstone (<a href="https://www.youtube.com/watch?v=NpVCxX2idUs"><strong>video</strong></a&…;). Keep your senses keen for changing conditions and signs of instability associated with wind-loading, wet snow and persistent weak layers.</p>

<ol start="1" type="1">
<li>Recently winds loaded slopes with large drifts&nbsp;could avalanche. In the Bridger and Northern Gallatin Ranges this weekend, skiers and riders triggered avalanches breaking up to several hundred feet wide and 18” deep, small slides and shooting cracks (<a href="https://www.mtavalanche.com/avalanche-activity"><strong>avalanche activity list</strong></a>). On Monday, Doug and his partner got brutalized by the wind to make a <a href="https://www.youtube.com/watch?v=Yaw6TM1HXIE"><strong>video</strong></a&…; telling us that wind-loading is a problem. Listen to his advice and avoid wind-loaded slopes.</li>
<li>Wet snow avalanches are a concern where the snowpack did not freeze last night and there was light rain yesterday (primarily the Bozeman and Big Sky areas). The snow will continue to weaken and wet snow avalanches will become more widespread with continued warm temperatures. Recognize increasing danger if you are sinking into unsupportable wet or slushy snow.</li>
<li>A weak layer of facets buried 6-18” deep will exacerbate the above issues. This layer could result in localized instability on its own, especially where there is more new snow. Dig and test the snowpack for these layers.</li>
</ol>

<p>Plenty of safe skiing and riding exists. However, stay heads up for changing conditions, signs of instability and utilize safe travel practices. The danger is MODERATE.&nbsp;</p>

<p>The mountains around Cooke City received 5” of new snow equal to 0.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314… water equivalent</a> in the last 48 hours and moderate winds are transporting snow onto slopes with weak layers buried around 2’ deep. Yesterday, a group of skiers near Goose Creek triggered an avalanche that broke 60’ wide and 12-16” deep on these weak layers. The skier lost a ski in the debris but was otherwise unharmed (<a href="https://www.mtavalanche.com/node/26049"><strong>photos and details</strong></a>). Riders and skiers triggered five other avalanches that we know of last weekend and Alex triggered a “whumph” on Sunday, indicating unstable snow (<a href="https://www.mtavalanche.com/avalanche-activity"><strong>avalanche activity list</strong></a>, <a href="https://www.youtube.com/watch?v=SxPaEcKATts&amp;list=PLXu5151nmAvT1nrM2…;). Larger avalanches like that on Mount Abundance last week are less likely but remain possible (<a href="https://www.youtube.com/watch?v=LHkbEAf1rlM&amp;list=PLXu5151nmAvT1nrM2…;

<p>Today, if you observe signs of instability, get unstable test scores or see a poor snowpack structure, make more conservative terrain choices. 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>