17-18

GNFAC Avalanche Advisory for Sun Apr 1, 2018

Snowpack and Avalanche Discussion

<p>The Bridger Range got 7” of new snow equal to .2” of snow water equivalent yesterday morning. Light to moderate westerly wind drifted this light powder into slabs that are possible to trigger today. These soft wind slabs are 6-12” thick and mostly found near ridgelines. Small avalanches of new snow are also possible on steep slopes, and wet loose avalanches are possible if the sun shines this morning. Avalanches in the new snow will probably be small today, and deeper avalanches are not likely.</p>

<p>Small wet loose avalanches and wind slabs can be deadly if they carry a person over cliffs or into trees, and a long ride in lower consequence terrain can still be harmful. Avoid wind loaded slopes if you see cracking of fresh drifts. Choose lower angle or lower consequence terrain if the snow surface gets moist or if you see dry or wet loose avalanches. Today, avalanches are possible to trigger and avalanche danger is <strong>MODERATE</strong>.</p>

<p>The mountains near Big Sky, West Yellowstone and Cooke City did not get any snow in the last 24 hours, and wind has been light to moderate out of the west-northwest. Strong westerly wind on Friday created fresh, 1-2 foot thick drifts that were easy to trigger. My partner and I were able to trigger these wind slabs near Cooke City on Friday, and we saw one that broke naturally (<a href="https://www.youtube.com/watch?v=epeP85qLoHg"><strong>video</strong></a>…;, </strong><a href="https://www.mtavalanche.com/images/18/natural-wind-slab-0"><strong>phot…;). Yesterday these slabs were less reactive and today they are difficult to trigger, but not entirely ruled out. Heavily wind loaded slopes, such as those near prominent ridgelines and below huge cornices, should be approached with caution.</p>

<p>Cornices are massive and dangerous (<a href="https://www.mtavalanche.com/images/18/winnebago-sized-cornices"><strong…;). They can fail under the weight of a person. Give them a wide distance along ridgelines and minimize time on slopes below. If the sun shines this morning, wet loose avalanches are possible on steep, sun exposed slopes. They will likely be small, but are something to keep an eye out for before clouds set in this afternoon. Today, avalanches are not likely or will be very small. Avalanche danger is rated <strong>LOW</strong>.</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&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Send us your observations on Instagram! #gnfacobs

Posting your snowpack and avalanche observations on Instagram (#gnfacobs) is a great way to share information with us and everyone else this spring.

GNFAC Avalanche Forecast for Sat Mar 31, 2018

Snowpack and Avalanche Discussion

<p>Yesterday, strong-gusty winds built slabs 1-2’ thick that failed naturally and with human triggers. Winds blew predominately out of the west-southwest, but seemed to affect all aspects and elevations. Yesterday, Alex found unstable conditions on wind loaded slopes around Cooke City (<strong><a href="https://www.youtube.com/watch?v=epeP85qLoHg">video</a&gt;, <a href="https://www.mtavalanche.com/images/18/natural-wind-slab-0">photo</a></s…;). Skiers up Hyalite also observed recent avalanches in wind loaded terrain.</p>

<p>Today, decreasing winds will reduce transport and give recently loaded slopes a bit of a breather. I don’t expect wind slabs to be as sensitive today, but I would still approach all wind loaded slopes with caution. Watch for signs of instability such as shooting cracks or recent avalanches and avoid steep, wind loaded slopes where these signs are present (<strong><a href="https://www.mtavalanche.com/images/18/small-wind-slab-hyalite">photo</a…;).</p>

<p>Strong winds also added significant weight and stress to cornices (<strong><a href="https://www.mtavalanche.com/images/18/winnebago-sized-cornices">photo</…;). These could fail naturally or under the weight of a single person. Give cornices a wide distance along the ridgelines and don’t have a picnic on slopes below.</p>

<p>There is a possibility the sun could come out this afternoon. This could create wet loose avalanches on steep, sun exposed slopes. It’s unlikely these will pose a significant threat, but it’s something to keep an eye out for later in the day.</p>

<p>Human triggered avalanches are possible today on wind loaded slopes which have <strong>MODERATE </strong>avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</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&gt;, email (<a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Send us your observations on Instagram! #gnfacobs

Posting your snowpack and avalanche observations on Instagram (#gnfacobs) is a great way to share information with us and everyone else this spring.

Recent snow was drifted by strong wind into 1-2' deep slabs that were reactive today (3/30). This snowmobile triggered slide is an indicator that fresh slabs are unstable and larger wind loaded slopes should be avoided.  Photo: GNFAC 

Cooke City, 2018-03-30