20-21

<p>There are a number of avalanches concerns today, stemming from the new snow, old snow, winds, and strong spring sun.&nbsp;</p>

<p>With generally light winds, the new snow does not have much cohesion and won’t cause widespread issues by itself. Stay on alert for isolated places where the new snow was drifted into more cohesive slabs. The additional weight of new snow will slow down the stabilization of older drifts. With shifting winds recently (including strong, unusual east winds in the Bridger Range last right), these drifts could be found on any aspect. If winds pick up this afternoon, watch for reactive, freshly forming drifts.</p>

<p>Underneath the recent snow, on some slopes there is a thin layer of weak snow (called near-surface facets). Dave and I spent the last two days digging snowpits looking for this layer in Cooke City and only found it on west facing slopes (<a href="https://www.youtube.com/watch?v=CZ27CVuKWuA"><strong><u>video</u></stro…;). We haven’t found a similar pattern in the rest of our advisory area. Even in Cooke City, I’m not confident that it is confined exclusively to a particular aspect. Expect to find this layer on west facing slopes near Cooke City, but it’s worth digging to look for it on any slope.&nbsp; If you find it, move to another slope where it doesn’t exist. There are many slopes with good riding conditions where the recent snow is well bonded.</p>

<p>Pay attention if the sun comes out, because if it does, you will quickly be able to trigger loose snow avalanches in the new snow. Roller balls and pinwheels are clear signs that the conditions for loose avalanches are developing.&nbsp;</p>

<p>While we haven’t seen an avalanche on the weak layers at the ground in weeks, the load of recent snow is starting to pile up. 2.5” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</u></a> has accumulated in many areas over the last week. I don’t expect avalanches to break near the ground today, but the nagging concern is starting to creep back in.&nbsp;</p>

<p>With the possibility of triggering a range of different types of avalanches today, the avalanche 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><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

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<p>Last night 7-10” of snow fell in the Bridger Range and the mountains around Big Sky. The <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2… water equivalent</u></a> is .3-.6” (low density powder) and will be easily blown around. Continued snow and wind will create drifts and unstable conditions. It will be easy to get windblown snow to crack and avalanche near the ridgelines where the drifts are thickest. Yesterday, skiers north of Bridger Bowl found wind drifts whumfing and cracking, a sign of what’s in store today. On a few slopes the weight of new snow may trigger a weak layer found 2-feet deep. This layer is not everywhere or easy to detect. Wind-loaded slopes will be simpler to identify and easy to avoid. Today, avalanches on wind-loaded slopes are likely and the avalanche danger is rated CONSIDERABLE. Slopes sheltered from the wind need to be assessed carefully with a <a href="https://youtu.be/sqn0KFZqXYs"><strong><u>quick stability test</u></strong></a> since these have a MODERATE avalanche danger.</p>

<p>The Gallatin Range, southern Madison Range, Lionhead area and Cooke City have gotten 2-3” of new snow and should expect a few more inches today. The wind has been gusting from the southwest at 25 mph, strong enough to build drifts throughout the day which should be avoided.&nbsp;</p>

<p>Dave and Ian are in Cooke City where they hunted for a thin layer of weak snow (near-surface facets) buried 1-2 feet deep. We know the layer exists in all our ranges, we just don’t know which specific slopes. Our tactic is the same everywhere: dig and test. Yesterday, Ian and Dave dug 6 snowpits and found the layer in their last one (<a href="https://youtu.be/m8-qxey7678"><strong><u>video</u></strong></a&gt;). Since the layer is close to the surface it is quick and easy to do stability tests (<a href="https://www.mtavalanche.com/images/21/stopping-quick-stability-test"><s…;), the only way to detect it. It is not obvious until the test column snaps. You can’t see it. Dave and I hunted for it on Mt. Blackmore on Tuesday and did not find it in our 4 pits (<a href="https://youtu.be/FAQK-UJK3aA"><strong><u>video</u></strong></a&gt;). When you do get it to break, it’s memorable because the layer propagates fast and clean. We have hard evidence of its existence on slopes in <a href="https://www.mtavalanche.com/node/24673"><strong><u>Hyalite</u></strong>…;, <a href="https://youtu.be/zCKlHstJTqc"><strong><u>McAtee Basin</u></strong></a> and the <a href="https://www.youtube.com/watch?v=TAWRM8yRgUM&amp;list=PLXu5151nmAvQDzKmH… </u></strong></a>and <a href="https://www.youtube.com/watch?v=U1b5LjWLTac&amp;list=PLXu5151nmAvQDzKmH…; Ranges. Assume it is underfoot until you prove otherwise. Slopes with this layer can avalanche and should be avoided. The avalanche danger throughout these ranges is rated 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><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>