19-20

Snowmobile triggered small slope Lionhead

LIONHEAD AREA
Lionhead Range
Code
SS-AMu-R2-D2
Latitude
44.72920
Longitude
-111.32300
Notes

From IG message: "Was riding up lions head today. Was on the same channel as another group and a member of their group came over the radio and said that he had to roll his sled and it triggered/buried his sled. Didn’t get much more info but he was very spooked over the radio. Looked hard on our way out and couldn’t find the slide."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Naturals in Storm Castle Creek

Storm Castle
Northern Gallatin
Code
SS-N-R3-D2-O
Elevation
8500
Aspect Range
E, W
Latitude
45.45040
Longitude
-111.22400
Notes

On Saturday 2/22/20 riders saw natural slides on east and west aspects 10 miles up Storm Castle creek. 

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural avalanche on Sphinx

Sphinx Mountain
Northern Madison
Code
HS-N-R3-D3-O
Elevation
9000
Aspect
SW
Latitude
45.15820
Longitude
-111.47700
Notes

On sunday 2/23/20 skiers near Sphinx Mtn. saw a recent  2-4' deep natural avalanche that broke on old persistent weak layers. Best estimate for timing is between 2/16 and 2/22. from IG: @skishot

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
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Mon Feb 24, 2020

Snowpack and Avalanche Discussion

<p>Today new snow and moderate wind create fresh slabs that can be triggered by a skier or snowmobiler. These fresh slabs increase the possibility of avalanches breaking 3-5 feet deep on weak sugary snow at the base of the snowpack. Through February we witnessed a widespread deep slab avalanche cycle in the Bridger Range, Hyalite and near Big Sky. Dozens of slopes avalanched with many slides snapping trees and running their maximum runout distance (<strong><a href="https://www.mtavalanche.com/node/21945">Saddle Peak</a>, <a href="https://www.mtavalanche.com/node/21971">Truman Gulch</a></strong>, <strong><a href="https://www.mtavalanche.com/node/22177">Maid of the Mist</a></strong>, <strong><a href="https://www.mtavalanche.com/node/22096">Blackmore</a></strong&gt;, <strong><a href="https://www.mtavalanche.com/node/22082">Wheeler</a&gt;, </strong><u><strong><a href="https://www.mtavalanche.com/node/22202">Emigrant</a></strong></u&gt;). Avalanches broke on all aspects and elevations, and there were relatively large avalanches in unusual areas like <strong><a href="https://www.mtavalanche.com/node/22088">Chestnut Mountain</a></strong> and <strong><a href="https://www.mtavalanche.com/node/22071">Lick Creek</a></strong>. Natural deep slab avalanches broke with relatively small additional storms as snowfall slowed down a week ago (<u><strong><a href="https://www.mtavalanche.com/images/20/naturals-north-flathead-pass">pho…;, <u><strong><a href="https://www.mtavalanche.com/images/20/natural-avalanche-near-flathead-p…;). Slopes that did not slide yet this season are near their breaking point, and with new snow and wind-loading today I do not trust those slopes.</p>

<p>Over the weekend a snowmobiler triggered a small slide on Scotch Bonnet near Cooke City (<strong><a href="https://www.mtavalanche.com/images/20/snowmobile-triggered-scotch-bonne…;), and skiers saw a large natural avalanche on the Sphinx in the Madison Range (<strong><a href="https://www.mtavalanche.com/images/20/natural-avalanche-sphinx">photo</…;). Weak layers might not be ready to hold this next storm, no matter how big. Browse the <u><strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche activity</a></strong></u> on our website to see where recent avalanches occurred and avoid similar terrain. Additionally, slopes that avalanched already this season should not be assumed stable. Carefully assess the stability of the new snow that sits on potentially weak bed surfaces of old slides.</p>

<p>Today, new snow, wind and buried weak layers create heightened avalanche conditions. Anticipate stability to decrease and take a step back from larger, committing objectives. Avalanche danger is MODERATE and will increase to CONSIDERABLE on wind loaded slopes where large natural avalanches are possible as snow and wind add weight this afternoon</p>

<p>The southern Madison Range, southern Gallatin Range and Lionhead area near West Yellowstone got a couple inches of snow last night with a couple more expected today. The snowpack there handled the February storms better than the rest of the advisory area. Doug and Ian rode into Cabin Creek last Wednesday and found a generally stable snowpack (<u><strong><a href="https://www.youtube.com/watch?v=2IzNvRo0R3w&amp;list=PLXu5151nmAvSbcbVf…;). Today moderate to strong wind will drift new snow into fresh slabs that are possible to trigger. Watch for cracking of the snow surface or snow blowing across ridgelines as a sign fresh drifts are unstable. Avalanches are possible on wind loaded slopes where danger is MODERATE. On non-wind loaded slopes avalanches are unlikely and danger is LOW.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<u><strong><a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a></strong></u>, email us (<u><strong><a href="mailto:mtavalanche@gmail.com&quot; target="_blank">mtavalanche@gmail.com</a></strong></u>), leave a VM at 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 and plan to attend one or two: Events and Education Calendar.

COOKE CITY

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

BOZEMAN

Small natural wet loose and wind slab in S. Gallatins

Specimen Creek
Southern Gallatin
Code
WL-N-R1-D1
Elevation
8500
Aspect
S
Latitude
45.02650
Longitude
-111.04800
Notes

From an obs on 2/23/20: "...today toured up above 9000 ft on Meldrum and some surrounding hills.... No cracking, collapsing, or naturals observed aside from some small wet loose that occurred yesterday in steep S rocky terrain at 8500 ft.... HS 150+ with depth hoar 130 down. The new snow will be falling on a variety of snow surfaces from crusts (E-S-W) to wind board (ridgelines) to NSFs (N). Temperatures warmed to above freezing today to at least 9000 ft. Winds increased to moderate out of the west by 1400 with some wind transport occurring at ridgelines."

From another group on Electric Peak on 2/23/20: "One recent natural avalanche near the ridgeline roughly 30 cm deep probably due to wind loading (D1) and a handful of natural loose wet (D1) avalanches on southerly aspects. Dug a quick pit on the face (10700’ NE 30 degree slope HS 190cm) and got an ECTP23 @ 35 below the surface on a hardness change below a 1F fresh windslab... Also, bulletproof windboard below the first roll (@10200’) and cranking winds!"

 

Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Wet Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Snowmobile triggered on Scotch Bonnet, Cooke City

Scotch Bonnet
Cooke City
Code
HS-AM-R1-D2-O
Elevation
10000
Aspect
SW
Latitude
45.07060
Longitude
-109.95200
Notes

"Seemed stability was getting better, but did see this minor slide that pulled out on Scotch Bonnet Mountain. Evidently triggered by a snowmobile sometime mid-day Saturday."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
R size
1
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
36.0 inches
Vertical Fall
300ft
Slab Width
30.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs: "Seemed stability was getting better, but did see this minor slide that pulled out on Scotch Bonnet Mountain. Evidently triggered by a snowmobile sometime mid-day Saturday (2/22)." Photo: R. Larson

Cooke City, 2020-02-23