18-19

GNFAC Avalanche Forecast for Sat Mar 9, 2019

Snowpack and Avalanche Discussion

<p>This recent storm was a bit of a bust. Snow totals were on the low end of forecasted amounts. Without a significant loading event, avalanche conditions aren’t as dangerous as they could be. Today the primary concern is a thin layer of facets buried 6-12” deep, possibly deeper on wind loaded slopes. This layer of facets has produced natural and human triggered avalanches in the mountains around Bozeman, Big Sky, and Cooke City. It doesn’t appear to be a problem in the mountains near West Yellowstone (<strong><a href="https://www.youtube.com/watch?v=oSgQnpBdkj0">video</a></strong>).</p&gt;

<p>Yesterday, skiers near Hyalite Peak in the northern Gallatin Range observed recent avalanche activity on wind loaded slopes and experienced unstable test results on facets buried 8-12” deep. Doug is in Cooke City and saw multiple human triggered slides that occurred yesterday. These slides only involved the new snow and mainly took place on south facing slopes (<strong><a href="https://www.mtavalanche.com/images/19/snomobiler-triggered-avalanche-ne…;). I highly recommend digging a quick snowpit and testing the new snow/old snow interface before committing to steep terrain (<strong><a href="https://www.youtube.com/watch?v=5X-yLt211Vw&amp;list=PLXu5151nmAvRNl9ku…;). &nbsp;</p>

<p>Slopes with wind drifted snow will be the most unstable and should be approached with caution (<u><strong><a href="https://www.youtube.com/watch?v=EP2us1tKA0E&amp;list=PLXu5151nmAvRNl9ku…;). Be especially observant of surface conditions in steep high consequence terrain. Even small slides can be deadly if they push you into trees or carry you over rocks (<strong><a href="https://www.mtavalanche.com/images/19/skier-triggered-mt-blackmore">pho…;). &nbsp;Conditions will become less touchy as time goes on, but human triggered slides remain possible today.</p>

<p>For this reason the avalanche danger is rated <strong>MODERATE</strong>.</p>

<p><strong>Avalanche Activity</strong>: Use the Regional Pages under the Forecast tap to find out what avalanche activity has been reported in the area you plan to visit.</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&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), 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.

COOKE CITY

This Friday and Saturday, Rescue Training and Snowpack Update. Friday 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.

Avalanches in new snow in Cooke City

COOKE CITY
Cooke City
Code
SS
Notes

These are observations from Doug Chabot's field trip on 3/8, Friday:

  1. One slide was triggered on a steep (40 deg) southeast facing slope at Round Lake outside Cooke City. It failed 8" deep on a layer of graupel and small facets. An adjacent hill slid at the same depth beforehand. This layer is not on most slopes, but as this slide shows it is on some. Doug was in the area and dug a pit in the crown soon after it was triggered.
  2. A slide under the cornice on the northeast face of Abundance looked to be 1 foot deep and 200' wide.
  3. A snowboarder reported triggering an 8" deep slab on the south face of Scotch Bonnett in one of the Rasta's.
Multiple Avalanches
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Problem Type
New Snow
Weak Layer Grain type
Near surface faceted particles
Weak Layer grain size
0.30mm
Slab Layer Grain Type
Precipitation Particles
Slab Layer Hardness
F+
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

This slide was triggered on a steep (40 deg) southeast facing slope at Round Lake outside Cooke City. It failed 8" deep on a layer of graupel and small facets. An adjacent hill slid at the same depth beforehand. This layer is not on most slopes, but as this slide shows it is on some. Doug was in the area and dug a pit in the crown soon after it was triggered. Photo: J. Fritz

Cooke City, 2019-03-08

This large natural avalanche occurred in the Absaroka Mountain Range outside of Paradise Valley. The slide broke hundreds of feet wide and 2-4' deep. It was likely triggered by a falling cornice. Notice the long distance it ran. This is a good reminder that low angle slopes can still be avalanche terrain. Always pay attention to the terrain above you. Photo: J. Negri  

Out of Advisory Area, 2019-03-08

GNFAC Avalanche Forecast for Fri Mar 8, 2019

Snowpack and Avalanche Discussion

<p>A few inches of snow overnight won’t be enough to spike the avalanche danger. Today, wind loaded slopes will be most prone to producing human triggered slides. Winds have been fairly light, but upper elevation gusts out of the west-southwest have been strong enough to transport snow and form fresh slabs below ridgelines. These slabs will be 1-2 feet thick and could fail under the weight of a skier or rider.</p>

<p>On some slopes, fresh wind slabs rest over a thin layer of facets that formed last weekend. Conditions will be touchier on slopes where this layer exists. On Wednesday, a skier unintentionally triggered a slide on Mt Blackmore that likely failed on this layer of facets (<u><strong><a href="https://www.mtavalanche.com/node/20322">details</a></strong></u&gt;). Fortunately, nobody was caught. We know this layer exists in the mountains around Bozeman and Big Sky (<u><strong><a href="https://www.youtube.com/watch?v=EP2us1tKA0E&amp;list=PLXu5151nmAvRNl9ku…;), but we’re unsure of its distribution in the mountains around West Yellowstone and Cooke City. Yesterday, I rode around Cabin Creek in the southern Madison Range and did not find this layer. My observations are consistent with what Karl found at Bacon Rind on Wednesday (<u><strong><a href="https://www.youtube.com/watch?v=5X-yLt211Vw&amp;index=2&amp;list=PLXu51…;

<p>Fortunately, you only need to dig about a foot deep to look for and assess this layer. This process only takes a few minutes and is a good insurance policy before jumping into steep terrain. If you’re feeling motivated, you can dig and test weak snow near the ground. The deep slab problem has improved significantly over the past few weeks (<strong><a href="(video)">video</a></strong>), but slides failing on weak snow buried deep in the pack can’t be entirely&nbsp;ruled out (<strong><a href="https://www.mtavalanche.com/images/19/big-avalanche-woody-ridge">photo<…;). This problem is most likely to occur in steep rocky terrain where the snowpack is highly variable.</p>

<p>Today, human triggered avalanches are possible and the avalanche danger is rated <strong>MODERATE</strong>. &nbsp;</p>

<p><strong>Avalanche Activity</strong>: Use the Regional Pages under the Forecast tap to find out what avalanche activity has been reported in the area you plan to visit.</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&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), 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.

COOKE CITY

This Friday and Saturday, Rescue Training and Snowpack Update. Friday 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.