24-25

GNFAC Avalanche Forecast for Fri Dec 20, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Triggering, large, dangerous avalanches remains </span></span></span></span></span></span><span><span><span><strong><span><span>likely </span></span></strong></span></span></span><span><span><span><span><span><span>today on slopes steeper than 30 degrees.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The reports continue to flow in of avalanches that broke during the snow and wind events this week. New reports yesterday include:</span></span></span></span></span></span></p>

<ul>
<li><span><span><span><span><span><span>Many natural avalanches near Cooke City, in the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32550"><span><span><span><span><span><…, Fischer and Sheep Creek drainages</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and another in </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32573"><span><span><span><span><span><… Goose Lake area</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> that looks to have broken on the mid-pack weak layers. Both parties also reported numerous cracks/collapses while travelling yesterday.</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>A natural on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32576"><span><span><span><span><span><… Mountain</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, near Big Sky and another on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32549"><span><span><span><span><span><… Peak</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, in Hyalite.</span></span></span></span></span></span></li>
</ul>

<p><span><span><span><span><span><span>There are widespread weak layers of sugary, faceted snow buried about 1-2 feet deep (videos from this week in </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=npOK4d94H50"><span><span><span><span><s… City</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.youtube.com/watch?v=4xSA_C9cPuc"><span><span><span><span><s…; Island Park</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.youtube.com/watch?v=RTUpUsNvXso"><span><span><span><span><s… Ridge</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=w-aXzlPHrYA"><span><span><span><span><s…;). These weak layers formed on top of the snowpack during the dry weather in the first two weeks of December. </span></span></span></span></span></span><span><span><span><strong><span><span>Persistent slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>have been breaking on these weak layers this week (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/avalanche-activity"><span><span><span><span… activity log</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). Faceted weak layers often remain easily triggered for a couple days after a loading event stops and we expect that to be true today. Slopes loaded or stiffened by the intense winds on Wednesday are likely to be the most easily triggered (with such intense winds, this will be many/most slopes).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanche conditions will slowly improve, but we’re not there yet. The avalanche danger is CONSIDERABLE. For today - avoid slopes steeper than 30 degrees. </span></span></span></span></span></span></p>

<p>&nbsp;</p>

<p><span><span><span><span><span><span>In the Bridger Range, triggering large avalanches is possible, but the weak layers are a bit stronger than elsewhere, so they won’t be quite as reactive. Yesterday, my partner and I found no signs of instability near the Throne, even while digging three pits to search for it, and felt comfortable tiptoeing into avalanche terrain (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=pA-bcDkn6RQ"><span><span><span><strong>…;). I’m extra skeptical of slopes that got heavily wind loaded on Wednesday, particularly because of a natural on Saddle Peak that broke 1-3 feet deep, and ran 1500 vertical feet (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32548"><span><span><span><strong><span…;).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you want to get into steeper terrain, start off with smaller slopes, slopes just steeper than 30 degrees, and ones that have good runouts below this in case you get surprised. Watch for signs of instability (cracking, collapsing, or poor test results) and be ready to quickly retreat to lower angled slopes if you find them.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE in the Bridger Range.</span></span></span></span></span></span></p>

<p>&nbsp;</p>

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Natural avalanche on Fan Mountain

Fan Mountain
Northern Madison
Code
SS-N-R2-D2
Latitude
45.29810
Longitude
-111.52400
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
2
D size
2
Vertical Fall
1000ft
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

E Face Mount Fox avalanche

Goose Lake
Cooke City
Code
SS-NC-R2-D2-O
Elevation
11000
Aspect
E
Latitude
45.11530
Longitude
-109.91400
Notes

From email: "Maiden Voyage to Goose Lake for the season today. Lots of wind drifted snow everywhere and challenging riding conditions. Performed Stability test on shoulder of Mount Fox NE facing slope at 10,300'. HS 180cm. ECTP2 40cm down on Buried Surface Hoar. ECTP 23 90cm down on MFcr with 1-2mm Facets. Saw several recent wind slab avalanches in steeper windloaded terrrain around Goose Lake, but limited activity was seen on Henderson. Lots of co/cr while touring on Mount Fox. D2 avalanche on east facing Mount Fox that appears to be on the SH layer, triggered by a cornice drop." 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Goose Lake/Mount Fox Obs

Date
Activity
Snowmobiling

From email: "Maiden Voyage to Goose Lake for the season today. Lots of wind drifted snow everywhere and challenging riding conditions. Performed Stability test on shoulder of Mount Fox NE facing slope at 10,300'. HS 180cm. ECTP2 40cm down on Buried Surface Hoar. ECTP 23 90cm down on MFcr with 1-2mm Facets. Saw several recent wind slab avalanches in steeper windloaded terrrain around Goose Lake, but limited activity was seen on Henderson. Lots of co/cr while touring on Mount Fox. D2 avalanche on east facing Mount Fox that appears to be on the SH layer, triggered by a cornice drop." 

Region
Cooke City
Location (from list)
Goose Lake
Observer Name
Ben Zavora

Natural Avalanche Activity, Cooke City

COOKE CITY
Cooke City
Code
SS-N-R3-D2.5-U
Elevation
10000
Aspect Range
N-NE-E
Latitude
45.02020
Longitude
-109.93800
Notes

Ob1: Photos 1-4, GNFAC

We rode out to Lulu Pass to look at the few avalanches that were reported yesterday on Henderson and Fisher Mtn. Today we did not see any avalanches that weren't previously reported, other than one small, but thick wind slab on south facing slope of Scotch Bonnet (photo). At least the avalanche on Fisher and one on Henderson broke near the ground (pics attached). Some slides were heavily refilled by drifted snow, so it was hard to tell how deep they broke.

Yesterday I saw a wide slab avalanche up on west Woody Ridge from town (photo attached). It happened late on Wednesday or overnight during or after the strong winds and snowfall.

 

Ob 2: B Fredlund, Photos 5-13

Quite a few natural avalanches observed north of Cooke City today.   Photos attached of:

5:  NE facing, 10,000, Miller Ridge

6:  E facing, 9900', Bull of the Woods Pass

7:  NE facing, 9700', Miller Ridge

8:  E facing, 10,200' Scotch Bonnet Mtn.

9:  E facing, 10,000 Mt. Henderson

10-12: NE- N facing, 10,000' Mt. Henderson

13:  NE facing, 10,000' Sheep Creek.

 

Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
2.5
Bed Surface
U - Unknown
Problem Type
Wind-Drifted Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year