18-19

Glide Plane Avalanche

"South side of the Glide Plane released as a glide avalanche last evening (May 12th) sometime around 6 pm according to source. Bed surface was ground in starting zone of wet clay soil sparsely covered in long grass.  Debris chunks, some snowmobile sized, rode up on surface and slid approx. 200 vert.  Debris could have bumped a tower on the old Alpine lift if it still lived there. Last freeze was 6 am on the 10th of May.  The high temperature on the 12th was 59 degrees at 4 pm." Photo and observartions: BBSP

Bridger Range, 2019-05-13

GNFAC Avalanche Forecast for Thu May 2, 2019

Snowpack and Avalanche Discussion

<p>NEW SNOW AND WIND LOADED SLOPES</p>

<p>Spring storms are notorious for depositing heavy amounts of snow in the mountains. Even with a deep and generally stable snowpack throughout the advisory area, heavy and rapid loads of new snow will decrease stability. The main problems to look out for are avalanches breaking within the new snow, wind slabs, and loose snow avalanches. The likelihood of triggering an avalanche spikes during and immediately after snowstorms. New snow instabilities tend to stabilize quickly, but it’s a good idea to give new snow a day to adjust before hitting big terrain. New snow instabilities can be difficult to assess, and spring storms bond to old snow differently across aspects and elevations. Conservative terrain selection is essential during and immediately following storms. Wind loaded slopes and slopes steeper than 35 degrees should be avoided for 24-48 hours after new snow and wind.</p>

<p>New snow can quickly change from dry to wet on a spring day, and stability can decrease rapidly with above freezing temperatures or brief sunshine. New snow may bond well early in the morning, and then easily slide later. Wet loose slides are likely during the first above freezing temperatures or sunshine immediately after a storm. Anticipate changes in snow stability as you change aspect or elevation, and over the course of the day. An early start is always an advantage. Be ready to change plans or move to safer terrain at the first signs of decreasing stability.</p>

<p>WET SNOW AVALANCHES</p>

<p>Spring and wet snow avalanches go hand-in-hand. Above freezing temperatures, rain, and/or intense sunshine cause the snow to become wet and weak, and make wet avalanches easy to trigger or release naturally. Conditions tend to become most unstable when temperatures stay above freezing for multiple days and nights in a row. Avoid steep terrain, and be aware of potential for natural wet avalanches in steep terrain above you, if you see:</p>

<ul>
<li>Heavy rain,</li>
<li>Above freezing temperatures for more than 24 hours,</li>
<li>Natural wet avalanches,</li>
<li>Roller balls or pin wheels indicating a moist or wet snow surface,</li>
<li>Or if you sink to your boot top in wet snow.</li>
</ul>

<p>In general, if the snow surface freezes solid overnight, the snowpack will be stable in the morning and stability will decrease through the day as snow warms up. The snow surface hardness, rate of warming, duration of sunshine, aspect and elevation determine how fast stability will decrease through the day. Be aware that sunny aspects may have a wet snow avalanche danger while shadier slopes still have a dry snow avalanche danger. Getting off of steep slopes should be considered when, or before, the above signs of instability are present. Wet snow avalanches, whether loose snow or slabs, can be powerful, destructive and very dangerous. Conservative terrain choices, starting early in the day, and careful observations can keep you safe. See Alex’s recent <a href="https://www.youtube.com/watch?v=foYa455ltOg&amp;list=PLXu5151nmAvRNl9ku…;, and this <a href="https://www.mtavalanche.com/blog/transitions-spring-snow-avalanche-prob… more spring travel advice.</p>

<p>CORNICES</p>

<p>Cornices along ridgelines are massive and can break under the weight of a person (<a href="https://www.mtavalanche.com/images/19/large-cornice-near-cooke-city"><s…;). Prolonged above freezing temperatures and rain make them weaker and possible to break naturally. They can break off suddenly and farther back than one might expect. Cornice falls can also entrain large amounts of loose snow or trigger slab avalanches. Stay far back from the edge of ridgelines and minimize exposure to slopes directly below cornices. Regardless of whether a cornice triggers a slide or not, a falling cornice is dangerous to anyone in its path.</p>

<p>DISCLAIMER</p>

<p>It does not matter if new snow falls or not, avalanches will continue to occur until the existing snowpack is mostly gone. Always assess the slope you plan to ride with diligence and safety in mind. Do not let your guard down. Travel with a partner, carry rescue gear and only expose one person at a time in avalanche terrain.</p>

<p>Have a safe and enjoyable spring and summer!</p>

<p>Doug, Eric, Alex, and Ian</p>

<p>We will update our <a href="https://www.mtavalanche.com/avalanche-activity">avalanche log</a>&nbsp;as snowfall continues.&nbsp;If you have any avalanche observations, please share them with us to include in this database. Contact us 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>

INFO AND ANNOUNCEMENTS

Sledders, mark your calendar for May 18, Sled Fest in Cooke City. It’s a fundraiser for the Friends of the Avalanche Center with a DJ, raffle prizes and BBQ on the mountain.

Bridger Bowl is closed for the season. Backcountry conditions exist and there is no avalanche hazard reduction or ski patrol services.

The Hyalite road is closed to motorized travel until May 16th. Bike and foot traffic is allowed.

GNFAC Avalanche Forecast for Mon Apr 29, 2019

Snowpack and Avalanche Discussion

<p>Recent new snow creates the main avalanche hazard this week. Avalanches breaking deeper than recent snow are unlikely until above freezing temperatures return for multiple days. On Saturday near Big Sky skiers found wind slabs that were easy to trigger (<strong><a href="https://www.mtavalanche.com/node/20692">photo</a></strong&gt;), and at Bridger Bowl skiers triggered loose new snow avalanches (<strong><a href="https://www.mtavalanche.com/node/20687">photo</a></strong&gt;). Similar avalanches are likely the next couple days (larger avalanches are possible) where wind drifts snow into thick cohesive slabs, or when the new snow gets wet with the first glimpse of sunshine or above freezing temperatures.</p>

<p>Thick drifts were formed by northwesterly wind yesterday, and today east wind will form fresh drifts where you might not usually find them. Avoid steep wind loaded slopes if you see cracking of fresh drifts or natural avalanches. Stability can change quickly when the sun comes out or temperatures get above freezing. Dry snow, drifted or not, will go from stable to unstable within minutes when it gets moist or wet. Wet slides are likely when the new snow warms up, and they can run long distances on firm snow underneath (<strong><a href="https://www.mtavalanche.com/images/19/natural-wet-loose-bridger-2">phot…;). These could be either wet loose or wet slabs, and either one will be forceful and potentially destructive.</p>

<p>Spring weather can quickly change between snow, sun, rain, and temperatures above and below freezing. Snow stability changes rapidly from day to day and hour to hour. Now is just as important as ever to be diligent with snowpack assessment and choose terrain carefully (<a href="https://www.youtube.com/watch?v=foYa455ltOg&amp;list=PLXu5151nmAvRNl9ku…;). See below&nbsp;for more spring snowpack and travel advice.</p>

<h3><strong>GIVE BIG GALLATIN VALLEY</strong></h3>

<p>May 2-3 from 6pm-6pm. Give Big Gallatin Valley is a 24-hour online and live celebration of giving created to connect generous community members with the causes they care about most. <a href="https://www.givebiggv.org/organizations/friends-of-the-gallatin-nationa… is the link</a> for more info and to support the Friends of the Avalanche Center during this event.</p>

<h3><strong>SHARE YOUR AVALANCHE OBSERVATIONS</strong></h3>

<p>We will update our <a href="https://www.mtavalanche.com/weather/wx-avalanche-log">weather and avalanche log</a> daily through April. It is a valuable resource for backcountry travelers through winter and spring. If you have any avalanche observations, please share them with us to include in this database. Contact us 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>

INFO AND ANNOUNCEMENTS

Bridger Bowl is closed for the season. Backcountry conditions exist and there is no avalanche hazard reduction or ski patrol services.

The Hyalite road is closed to motorized travel until May 16th. Bike and foot traffic is allowed.

Sledders, mark your calendar for May 18, the 3rd Annual Sled Fest in Cooke City. It’s a fundraiser for the Friends of the Avalanche Center with a DJ, raffle prizes and BBQ on the mountain.

Skier triggered wind slab near Beehive Basin

Hellroaring Creek
Northern Madison
Code
SS-AS-R2-D1.5-I
Elevation
10000
Aspect
N
Latitude
45.35810
Longitude
-111.37600
Notes

From e-mail: “We found soft snow and great skiing in the morning, with a few wind affected pockets (my partner triggered a wide but thin wind slab coming into the hellroaring basin). By noonish the winds picked up quite a bit, quickly creating thin and sensitive wind slabs as we made our way down the SE face.  The small slides we created could have been dangerous in exposed terrain.”

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
R size
2
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
6.0 inches
Vertical Fall
400ft
Slab Width
30.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year