22-23

From email: "...cornice collapse. One block in the debris pile was probably the size of my airplane - a giant ass snowball." Photo: Austin Timm, Yellowstone Air Service

Northern Madison, 2023-04-10

Wet Snow Avalanches, North Madison Range

Date

From email: "This afternoon en route back to Livingston from Idaho, lots of slide activity at all elevations…

The first picture is the cornice collapse. One block in the debris pile was probably the size of my airplane - a giant ass snowball. 

The next few photos are wet slab a mile north along the same ridge, location: approximately 1-2 miles SW of the coordinate photo (it took me a minute to get cords up). Elevation of both approximately 9,800-10,000. 

Too many point releases to count in every range I’ve crossed today…"

Region
Northern Madison
Location (from list)
NORTHERN MADISON RANGE
Observer Name
Austin Timm, Yellowstone Air Service

GNFAC Avalanche Forecast for Mon Apr 10, 2023

Snowpack and Avalanche Discussion

<p>Last night, temperatures remained above freezing in all but the highest elevations. Wet snow avalanches dominate our list of concerns. School bus-sized cornices may collapse, and the snow will get wet early in the day, weakening to the point of failure. By 10:30 am yesterday, we witnessed two wet, loose snow avalanches in Flanders Creek and the upper 6-8” of snow slid cohesively on steep rollovers as we made our exit shortly after noon (<a href="https://www.youtube.com/watch?v=nyhShY4u7LM"><strong><span>video</span>…;). The Yellowstone Club Ski Patrol observed natural wet snow avalanches on southerly aspects (<a href="https://www.mtavalanche.com/node/29041"><strong><span>details</span></s…;). On Saturday, a south-facing avalanche path above Quake Lake buried the highway in wet debris (<a href="https://www.mtavalanche.com/node/29022"><strong><span>photos and details</span></strong></a>). Wet snow avalanches will start earlier and be larger than yesterday. Be off and out-from-under steep slopes before the crust breaks down and the upper 6” of snow turns to mush. Wet snow avalanches can run into the flats, crossing and groomed paths and spilling onto roads.</p>

<p>Dry snow concerns continue with wind slabs and deeply buried persistent weak layers at the forefront. Near Big Sky Resort yesterday, a skier triggered an avalanche that ran full path, the third close call in Lone Lake Cirque in recent weeks (<a href="https://www.mtavalanche.com/node/29042"><strong><span>details</span></s…;). Ski patrol observed a recent dry slab avalanche on the Sphinx (<a href="https://www.mtavalanche.com/node/29041"><strong><span>details</span></s…;). Last weekend’s storm brought very large avalanches breaking on persistent weak layers buried in January (<a href="https://www.mtavalanche.com/node/29012"><strong><span>Northern Madison Range</span></strong></a>, <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</span></…;, <a href="https://www.mtavalanche.com/node/28900"><strong><span>Bridger Range</span></strong></a>,<strong> </strong><a href="https://www.mtavalanche.com/node/29039"><strong><span>Bridger Range 2</span></strong></a>).</p>

<p>The danger from wet snow avalanches will begin the day as CONSIDERABLE and increase to HIGH. Avoid steep slopes and runout zones as the day warms.</p>

<p>Below-freezing temperatures in Cooke City will delay but not prevent wet snow avalanches. Be off and out-from-under steep slopes by the time the surface crusts break down and the upper 6” of the snowpack gets wet. Avalanches can run into the flats and cross groomed paths. Temperatures pushing near 50 degrees F will weaken cornices and we may see a few collapse today.</p>

<p>Dry snow avalanche concerns remain, including avalanches failing within slabs of recently wind-drifted snow and on deeply buried persistent weak layers. On Thursday, a skier triggered a wind slab on Scotch Bonnet Mountain (<a href="https://www.mtavalanche.com/node/28986"><strong><span>details and photo</span></strong></a>), and avalanches released 1-3 ft deep on wind-loaded slopes (<a href="https://www.mtavalanche.com/node/28994"><strong><span>Cooke details 1</span></strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/29005"><strong><span>Cooke details 2</span></strong></a>). Deep slab avalanches on <a href="https://www.mtavalanche.com/images/23/huge-deep-slab-mt-abundance"><str…. Abundance</span></strong></a> and on <a href="https://www.mtavalanche.com/node/28924"><strong><span>Woody Ridge</span></strong></a> failed one week ago during a storm. Dig down a few feet to investigate for instability below last week’s snow. Avoid steep, wind-loaded and consequential avalanche terrain to manage deep slab instability.</p>

<p>The avalanche danger is CONSIDERABLE due to the wide array of avalanche concerns, including increasing wet snow danger.</p>

<p>Please share avalanche, snowpack or weather observations via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

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Skier Triggered Avalanche, Lone Lake Cirque

Lone Lake Cirque
Northern Madison
Code
HS-AS
Latitude
45.27710
Longitude
-111.46400
Notes

From email: "There was yet another skier-triggered avalanche out in the Lone Lake Cirque this afternoon.  Sounds a like a cornice trigger (not sure if it was intentional) that triggered a large slab on the slope below and ran full track.  I do not believe the involved party rode the avalanche but it was another close call.  This was adjacent to the one triggered a couple of days ago which was adjacent to the one triggered a few days before that." 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Skier
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Wet Snow Avalanches Near Pioneer Mountain

Yellowstone Club
Northern Madison
Code
WL-N
Latitude
45.23110
Longitude
-111.44100
Notes

From Obs: "Today we observed wet loose avalanche activity on the southerly aspects in the mountains around Pioneer mountain. We also observed one dry slab avalanche on a NE aspect of Sphinx mountain at approximately 9,000’."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Wet and dry avalanche activity in the backcountry

Date

Today we observed wet loose avalanche activity on the southerly aspects in the mountains around Pioneer mountain. We also observed one dry slab avalanche on a NE aspect of Sphinx mountain at approximately 9,000’. 

Region
Northern Madison
Location (from list)
Sphinx Mountain
Observer Name
YC Ski Patrol