24-25

GNFAC Avalanche Forecast for Fri Feb 14, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><strong><span><span>Wind slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>are the primary concern today. There are a couple inches of new snow already, with a few more on the way today and winds strong enough to drift that new snow. Thin fresh drifts will be easily triggered today. Triggering older, somewhat thicker wind slabs that formed with high winds over the last couple days is also a possibility.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Persistent Slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>are still possible, breaking a couple feet deep on weak layers that formed at the end of January, as evidenced by a small slide triggered yesterday in the Lionhead area (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34156"><span><span><span><span><span><…;), an avalanche near Cooke City triggered by a cornice within the last 36 hours that looks have broken on deeper weak layers (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/cornice-triggered-avalanche-miner…;) and a couple slides in the Taylor Fork that likely broke last weekend (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=wZ3k35z5Ej8&amp;embeds_referring_euri=h… Fork video</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). These slides are more likely to be triggered on windloaded slopes, with thicker and more cohesive slabs.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Identifying and avoiding windloaded slopes is the best strategy to reduce your chances of triggering any sort of avalanche today.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are also the primary avalanche problem around Bozeman and Big Sky. It hasn’t snowed much yet and not too much will pile up today, but even without new snow yesterday, we got reports of active wind loading and several small slides (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34144"><span><span><span><span><span><… fork of Hyalite observation</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34137"><span><span><span><span><span><…. Blackmore observation</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Identifying areas of wind deposited snow and either avoiding them or assessing how well they’ve bonded is the primary risk management recommendation today. Persistent weak layers are less widespread in these areas compared with further south, but keeping your eye out for them (by digging a snowpit) is still not a bad idea&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE today on wind loaded slopes and LOW on non-wind loaded slopes.</span></span></span></span></span></span></p>

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Small slide in Lionhead

Lionhead Ridge
Lionhead Range
Code
AMu-R1-D1
Latitude
44.71450
Longitude
-111.31800
Notes

From FB message: "Small slide in lower elevation back by lionshead"

Number of slides
1
Number caught
0
Number buried
0
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
1
D size
1
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Small slide in lower elevation

Date
Activity
Snowmobiling

From FB message: "Small slide in lower elevation back by lionshead"

Region
Lionhead Range
Location (from list)
Lionhead Ridge

Small Wind Slab Taylor Fork

Sunlight Basin
Southern Madison
Code
SS-N-R1-D1
Elevation
9150
Aspect
E
Latitude
44.97310
Longitude
-111.31000
Notes

We saw one wind slab avalanche (R1, D1) in Sunlight Basin. This slide was fresh from this morning or yesterday. 50 feet wide and 6 inches deep. 

 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Wind Slab
Slab Thickness
15.0 centimeters
Vertical Fall
50ft
Slab Width
50.00ft
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Persistent Slab Avalanches in Taylor Fork

Taylor Fork
Southern Madison
Code
SS-AM-R2-D2-O
Elevation
9200
Aspect Range
E-N
Latitude
45.06070
Longitude
-111.27200
Notes

We rode into the Taylor Fork, down into the bottom of Sunlight Basin, across Carrot Basin and to the Wilderness Boundary. We saw four persistent slab avalanches that likely broke last weekend or at the beginning of the week. All appeared to be snowmobiler-triggered R1-2, D1.5-2 avalanches at broke of the January layer of near-surface facets and surface hoar. Additionally, we saw one wind slab avalanche (R1, D1) in Sunlight Basin. This slide was fresh from this morning or yesterday. 

We dug a crown profile for the persistent slab avalanche in Sunlight (attached). ECTN24 on the SH layer buried 50 cm (20") deep.

Number of slides
4
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Slab Thickness
50.0 centimeters
Vertical Fall
100ft
Slab Width
200.00ft
Weak Layer Grain type
Surface Hoar
Weak Layer grain size
8.00mm
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Buried layers of surface hoar often show up a stripe in a snowpit wall (other things such a thin melt-freeze crust can look similar but feel much differently). A snowmobiler-triggered avalanche in Sunlight Basin broke on this weak layer of feathery surface hoar. Photo: GNFAC

Southern Madison, 2025-02-13