23-24

GNFAC Avalanche Forecast for Fri Nov 17, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Our warm fall continued at lower elevations, with wheels and hiking boots feeling more appropriate than sleds and boards. However, the story at higher elevations is different. Skiers and riders in the Bridger and Northern Gallatin Ranges and near Cooke City have reported avalanches in the last two weeks (</span></span></span></span></span></span><a href="https://mtavalanche.com/avalanche-activity"><span><span><span><strong><… activity</span></span></u></span></strong></span></span></span><span><span><span><span><span><u><span><span> </span></span></u></span></span></span></span></span><span><span><span><strong><span><u><span><span>log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). This included skier-triggered slides in </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29256"><span><span><span><strong><span… Great One</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>(11/8) and on</span></span></span></span></span></span><span><span><span><strong><span><span> </span></span></strong></span></span></span><a href="https://www.mtavalanche.com/node/29284"><span><span><span><strong><span… Blackmore</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> (11/12). Both of these slides occurred in steep, high-consequence terrain and, thankfully, had happy endings. Anyone traveling in snow-covered terrain, whether they be a skier, rider, hunter, climber, or hiker, should adhere to the avalanche fundamentals. Avoid steep slopes or take precautions by traveling with a partner, carrying avalanche gear, including a beacon, shovel, and probe, and only exposing one person at a time to steep slopes.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Conditions generally trended toward stability during our warm week without new snow, but strong wind built thick drifts on some slopes. Treat slopes with large mounds of wind-loaded snow with suspicion by testing and looking for signs of instability or avoiding them.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Stability and strength are not synonymous, while stability has improved, our thin, early-season snowpack is weakening as it transforms into sugary facets. This is the foundation upon which our snowpack will be built. On Wednesday, Ian saw evidence of this weakening while working on weather stations in the Centennial Mountains (</span></span></span></span></span></span><a href="https://mtavalanche.com/node/29287"><span><span><span><strong><span><u>… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). When winter finally arrives, snow will fall on a layered snowpack composed of weak facets on many upper-elevation slopes. At lower elevations, snow will fall on dirt, and the evolution of the snowpack will begin.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>We are grateful to the groups who have reported avalanches so far this season. These observations help us provide the broader community with life-saving information. Your observations are more important than ever during the early season as we get to know this season’s developing snowpack. If you get out, please share avalanche, snowpack or weather observations via our </span></span></span></span></span></span><a href="blank"><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><a href="mailto:mtavalanche@gmail.com"><span><span><span><strong><span><u><span>…;), phone (406-587-6984), or Instagram (#gnfacobs).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>We’ll update the Weather and Avalanche Log daily and issue pre-season bulletins as needed throughout the fall as conditions warrant.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanche season is here at higher elevations. Natural and human-triggered avalanches in the last two weeks are clear evidence of this. Slopes with large drifts of wind-loaded snow are the most likely to slide. While stability has improved in the week without new snow, adhere to avalanche fundamentals whenever you are near steep snow-covered slopes. Carry rescue gear, expose a maximum of one person at a time to steep slopes, and watch and test for signs of instability.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>On Wednesday, Ian saw evidence that the 20” of snow at 8800’ is weakening at our Sawtelle Weather Station. This will be the foundation of this season’s snowpack (</span></span></span></span></span></span><a href="https://mtavalanche.com/node/29287"><span><span><span><strong><span><u>… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).</span></span></span></span></span></span></p>

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

Went to do maintenance on the Sawtelle Snowfall weather station at 8800 ft just off the Sawtelle Mountain Road. Continuous snowcover starts around 8000 ft. At 8800 ft there is ~20" of snow with a mix of hard crusts and weak facets. These weak layers near the ground will be something to watch once snows again. Photo: GNFAC

Island Park, 2023-11-17

Went to do maintenance on the Sawtelle Snowfall weather station at 8800 ft just off the Sawtelle Mountain Road. Continuous snowcover starts around 8000 ft. At 8800 ft there is ~20" of snow with a mix of hard crusts and weak facets. These weak layers near the ground will be something to watch once snows again. Photo: GNFAC

Island Park, 2023-11-17

Sawtelle Weather station maintenance

Date

Went to do maintenance on the Sawtelle Snowfall weather station at 8800 ft just off the Sawtelle Mountain Road. Continuous snowcover starts around 8000 ft. At 8800 ft there is ~20" of snow with a mix of hard crusts and weak facets. These weak layers near the ground will be something to watch once snows again. 

Region
Island Park
Location (from list)
Sawtelle Peak
Observer Name
Ian Hoyer

Skier triggered Windslab Mt Blackmore

Mt Blackmore
Northern Gallatin
Code
ASu-R2-D2-O
Elevation
9750
Aspect
E
Latitude
45.44430
Longitude
-111.00200
Notes

Skiers reported triggering an avalanche on the east face of Mt. Blackmore on Sunday.

Number of slides
1
Number caught
0
Number buried
0
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Vertical Fall
400ft
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year