22-23

Exposed crown on Leggat mountain, Tobacco Roots

Date
Activity
Skiing

6” of powder snow on northerly aspects above 9,000’. Wet powder of diminishing depth as elevation dropped. Supportable snow underlying everything. Didn’t dig a pit.

Region
Out of Advisory Area
Location (from list)
Tobacco Root Mountains

Spooky Snowpack in the Western T-Roots

Date
Activity
Skiing

While skinning into Big Bear gulch, off Wisconsin creek, we encountered a couple of small whumphs in a flat meadow below treeline. We also encountered one instance of localized cracking within the trees, near the hollow created by a dead tree. At the top of the ridgeline there were small cornices, and we noticed significant wind loading higher up on Old Baldy mountain.

In our east facing pit, just below the Little Bear ridgeline, we found a large melt freeze crust complex near the surface, interspersed with layers of much softer snow and NSF. Below the stout crust layers, the snowpack drastically reduced in hardness, with fist hardness facets near 50cm from the ground. We had moderate CT results (CT 12 Q2 @140cm) within the crust complex, and more difficult CT results (CT 23 Q2 @30cm) within a layer of large (3mm) striated depth hoar near the ground. Our ECT test resulted in an ECTX, possibly indicating the strength of the crusts, which neither skis nor boots would penetrate through. Our ECT column did pull out of the wall as a cohesive block when we applied shear from behind. Our pit profile was submitted through Snowpilot.

Based on these observations, and the warming we believed would occur later in the day, we decided to not ski off of Old Baldy mountain, and rather took some laps at a nearby low-angle meadow. 

Region
Out of Advisory Area
Location (from list)
Tobacco Root Mountains
Observer Name
Wyatt Hubbard

Beehive basin

Date
Activity
Skiing

Usual spring conditions. Out farming corn snow. Saw some activity from the warming sun.

Region
Northern Madison
Location (from list)
Beehive Basin
Observer Name
Conor skibum powhound

GNFAC Avalanche Forecast for Mon Apr 17, 2023

Snowpack and Avalanche Discussion

<p>Avalanche conditions change rapidly in the springtime, and we must adapt quickly to these changes. Warm daytime temperatures on Monday and Tuesday make wet snow avalanches the dominant concern. This weather yields to cooler temperatures and snowfall, increasing the danger of avalanches within the new and wind-drifted snow. On top of these, cornice fall and the chance of deeper avalanches releasing on persistent weak layers are possible.</p>

<p><strong>The Breakdown:</strong></p>

<p><strong>Wet snow avalanches</strong> <strong>-</strong> Well above-freezing temperatures and sunshine on Monday will break down superficial crusts and make wet loose avalanches possible. Move to cooler aspects if the surface snow becomes wet and sloppy. Snow and cooler temperatures will largely shut down wet snow concerns by midweek. However, be on guard if the warm spring sun starts moistening the surface even for brief periods. On Sunday, a group on the Fin near Cooke City triggered a wet snow avalanche that carried a long distance (<a href="https://www.mtavalanche.com/node/29117"><strong><span>details</span></s…;).</p>

<p><strong>Cornice Fall</strong> <strong>-</strong> These overhanging ledges of snow grew to epic proportions during the winter. They can break far back from their edge this time of year. Avoid traveling on top of them and minimize the time spent below. Cornice fall itself is dangerous, and it often triggers avalanches on the slopes below. Recent collapses occurred on <a href="https://www.mtavalanche.com/images/23/cornice-fall-mount-abundance"><st…. Abundance</span></strong></a> and in the <a href="https://www.mtavalanche.com/images/23/giant-cornice-collapse-north-madi… Madison Range</span></strong></a>.</p>

<p><strong>New and wind-drifted snow</strong> <strong>-</strong> Snowfall this week will increase the danger of avalanches within the new and wind-drifted snow. The more it snows, and the more it blows, the more dangerous conditions will get. Before the storm arrives, dry slab avalanches are possible on higher elevation slopes where the snow remains powdery. This Saturday, outside the advisory area in the Crazy Mountains, a group triggered an avalanche that broke 50’ wide and ran 1000’ on a high elevation, north-facing slope (<a href="https://www.mtavalanche.com/node/29120"><strong><span>details</span></s…;).</p>

<p><strong>Deep Slab Avalanches and Persistent Weak Layers</strong> <strong>-</strong> The recent melt-down created a thick crust on many slopes and made triggering deep slab avalanche much less likely, but they remain possible, especially on high-elevation slopes where the melt-freeze crusts aren’t as robust. Avoid this problem by choosing simple, lower-angle terrain, especially during and immediately after storms. Deep slab avalanches released during the first week of April in the Northern Madison Range (<a href="https://www.mtavalanche.com/node/29012"><strong><span>1</span></strong>…;, <a href="https://www.mtavalanche.com/node/29119"><strong><span>2</span></strong>…;), <a href="https://www.mtavalanche.com/node/29004"><strong><span>Southern Gallatin Range</span></strong></a>, <a href="https://www.mtavalanche.com/node/28949"><strong><span>Lionhead Area</span></strong></a> and <a href="https://www.mtavalanche.com/node/28900"><strong><span>Bridger Range</span></strong></a>.</p>

<p>We are updating our <a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><span>ava… and weather log</span></strong></a> daily and posting relevant changes to the avalanche conditions so you can track the weather and how it affects these problems. Practice the fundamentals of avalanche safety until the snow melts. Every member of a group carries a beacon, shovel and probe. Signs of instability turn us back to lower-angle terrain. Expose only one team member at a time to avalanche terrain while the rest of the group watches from a safe position.</p>

<p><span>We will issue spring snowpack and weather updates twice a week through April, and we will share relevant avalanche and snowpack information on our website and social media. If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</span></p>

Info and Reminders

Bridger Bowl Ski Area is closed, and ski patrol is no longer performing rescues and making terrain closure decisions for you (video).

Hyalite Canyon road is closed for motorized use until May 16.

Dry loose avalanche in Crazies

Crazy Peak
Out of Advisory Area
Code
SS-ASu-R2-D2-I
Aspect
N
Latitude
46.03120
Longitude
-110.30500
Notes

From Obs: "This afternoon my group triggered a dry-loose avalanche on the north face of Big Timber Peak in the Crazies. The slide was about 12 inches deep, 50 feet wide, and ran about 1,000 vertical feet. Thankfully, no one was injured. We didn’t officially measure the slope angle but we’re estimating it to be in the 38-degree zone—prime avalanche territory. The slide consisted of new snow that fell during this recent storm. It hadn’t bonded to the thick crust underneath and released during the second skier’s run."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
12.0 inches
Vertical Fall
1000ft
Slab Width
50.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Deep Slab S Fork Hellroaring

NORTHERN MADISON RANGE
Northern Madison
Code
HS-N-R3-D3-O
Elevation
9800
Aspect
N
Latitude
45.29520
Longitude
-111.41000
Notes

From Obs: "Was able to spot a deep slab avalanche from Gallatin peak, slab was at the headwaters of S Fork Hellroaring (N aspect @ 9800) Hard to tell when this released as it was a few miles away, I would estimate the crown being around 10 feet. Observed a small storm slab on a north aspect as well (1-2 foot crown). Also saw a few dozen wet slides that released earlier this week, some tearing all the way to the ground."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
3
D size
3
Bed Surface
O - Old snow
Slab Thickness
72.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs: "Was able to spot a deep slab avalanche from Gallatin peak, slab was at the headwaters of S Fork Hellroaring (N aspect @ 9800) Hard to tell when this released as it was a few miles away, I would estimate the crown being around 10 feet. Observed a small storm slab on a north aspect as well (1-2 foot crown). Also saw a few dozen wet slides that released earlier this week, some tearing all the way to the ground." Photo: T. Saulnier

Northern Madison, 2023-04-16

Wet Snow Avalanche on The Fin

The Fin
Cooke City
Code
WL-AS-R2-D1.5
Elevation
9900
Aspect
E
Latitude
45.00460
Longitude
-109.95800
Notes

From Obs: "Had some loose wet slides on the fin today just after noon. Was about 3-6” deep at the new/old snow interface. Slide was slow moving but carried farther than we thought."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Skier
R size
2
D size
1.5
Problem Type
Wet Snow
Slab Thickness
5.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year