22-23

GNFAC Avalanche Forecast for Thu Mar 30, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>There are a few avalanche concerns today, but none are widespread. The snowfall from the weekend was blown into drifts near the ridgetops which could be triggered; cornices grew and could break; a weak layer of facets might be found a couple feet under the surface; and a weak layer 3-5 feet deep could avalanche, although these are rare.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The first three items on the list are things we can avoid and navigate around: turn around when wind-drifts crack; on ridges make sure your skis or sled are over solid ground instead of a snow overhang; and dig in the upper 3 feet of the snowpack to test the stability of the new snow. For the fourth item, deep slab avalanches, there’s not much you can do other than avoid avalanche terrain or accept that these rare, big slides, are lurking like sharks with you as chum.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Over the last few days there have been natural avalanches in the </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28848"><span><span><span><strong><span>… Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, up </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28861"><span><span><span><strong><span>…;, on </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28870"><span><span><span><strong><span>… Ridge</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, and a couple deep ones a week ago in </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28798"><span><span><span><strong><span>…; and </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28785"><span><span><span><strong><span>… City</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>. Avalanches remain possible. To make your pre-trip homework easier check out our </span></span></span></span></span></span><a href="http://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span>… and Avalanche Log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> which has a full listing of the natural and human-triggered slides, and watch our field videos where </span></span></span></span></span></span><a href="https://youtu.be/M3hp2s4iQ1o"><span><span><span><strong><span><u><span>… describes the conditions on Buck Ridge</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://youtu.be/8gXkzoEbk6Q"><span><span><span><strong><span><u><span>… talk about digging under the new snow in the Bridger Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://youtu.be/jrjIs789meI"><span><span><span><strong><span><u><span>… gives advice on terrain selection</span></span></u></span></strong></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>The avalanche danger is rated MODERATE on all slopes.&nbsp;</span></span></span></span></span></span></p>

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

<p><span><span><span><span><span><span>There are a few avalanche concerns today, but none are widespread. The snowfall from the weekend was blown into drifts near the ridgetops which could be triggered; cornices grew and could break; a weak layer of facets might be found a couple feet under the surface; and a weak layer 3-5 feet deep could avalanche, although these are rare. Dig, test and turn around if you see any recent avalanches or find instability. </span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

Events and Education Calendar.

Natural avalanches in Hyalite

Hyalite - main fork
Northern Gallatin
Code
Latitude
45.44720
Longitude
-110.96200
Notes

On my walk up to divide today 3/28 I noticed a few small storm slabs that broke on the west side of the main fork of hyalite off the summer trail.  This area had similar storm slabs that broke back in mid February during a large storm 

up in the alpine there were no avalanches to report 

Number of slides
3
Number caught
0
Number buried
0
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural avalanche on Buck Ridge

Buck Ridge
Northern Madison
Code
N
Elevation
8900
Aspect
SE
Latitude
45.17190
Longitude
-111.38000
Notes

From IG:

Think this was a recent natural up buck I saw today. Didn’t get close enough to see but looked like it was a big crown… down low 8900ish SE

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
Problem Type
Persistent Weak Layer
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Large avalanche on Bridger Peak

Bridger Peak
Bridger Range
Code
N
Elevation
10000
Aspect
E
Latitude
45.77010
Longitude
-110.94000
Notes

Two large, widely propagation fractures visible through a hole in the cloud cover Monday A.M. from Bridger Canyon Dr. Upper slab failure evidently stepped down to a deeper layer estimated 400' below upper crown. Both crowns appeared to be similar depth. Also visible were debris toes further to the North that had run mostly full path. Looked like it was already covered up yesterday (tues).

A second ob via phone message:

A large natural avalanche occurred on the north summit of Bridger Peak yesterday (Monday, 27 March). The crown line was complex.

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Wed Mar 29, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>The northern Gallatin Range is windier than other areas. Beginning last night gusts from the southwest are blowing 30 mph. There is 2+ feet of snow to blow around and newly formed wind slabs will be easily triggered today. Climbers need to be extra careful in gullies and skiers need to be on the lookout for any shooting cracks. On slopes not wind loaded, dig and test the top 3 feet of the snowpack to see how the new is bonding to the old surface. A few natural slides were seen that were breaking under the new snow (</span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28861"><span><span><span><strong><span>… and photos</span></span></u></span></strong></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>This range has also had deep and scary avalanches from weak layers 5+ feet deep that are breaking in a random way (</span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28798"><span><span><span><strong><span>… and photo</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). While rare, these slides are deadly. Notching back slope angles to below 30 degrees will keep you safe, yet if you decide to get into avalanche terrain only expose one person at a time.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The danger is rated CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Ridgetop wind is blowing SE-SW at moderate speed creating wind drifts that are being fed by last weekend’s powder (14-32”). These drifts could crack and avalanche under your feet or machine. Ian and I went into the Throne in the Bridger Range yesterday. Underneath the new snow we found a layer of facets that broke in our stability test that was also responsible for avalanche activity during and immediately after the storm (</span></span></span></span></span></span><a href="https://youtu.be/8gXkzoEbk6Q"><span><span><span><strong><span><u><span>…; and </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28856"><span><span><span><strong><span>…;). Skiers also triggered slides </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28850"><span><span><span><strong><span… Big Sky Ski Resort</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28823"><span><span><span><strong><span… Ellis</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>. It’s worth taking a few minutes to dig down 3 feet and test the stability before committing to avalanche terrain.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Complicating our stability assessment is the possibility of deep slab avalanches, most prominent in the southern ranges. Buried 3-5 feet deep is a weak layer that could break on a few, isolated slopes. Cooke City had more than a fair share of these, the most recent was last Thursday near Chimney Rock when 2 sledders were caught and 1 was badly injured (</span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28785"><span><span><span><strong><span>… and photos</span></span></u></span></strong></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>Wind-loading and a recently buried weak layer are the primary avalanche concerns today. These can be navigated with awareness and investigation of the snowpack. Slopes that could produce large, deep avalanches, on the other hand, are not easily identified. However, triggering them is most likely in thinner areas of the snowpack, but those areas are not visible on the surface. This presents a quandary. Dave explains how we can stack the deck in our favor by choosing terrain that is safer in his 2-part video series from Cooke City (</span></span></span></span></span></span><a href="https://youtu.be/nJWsF4g2Rjc"><span><span><span><strong><span><u><span>… 1</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://youtu.be/jrjIs789meI"><span><span><span><strong><span><u><span>… 2</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). In essence, either avoid avalanche terrain or choose terrain lacking traps like trees and cliffs.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is rated MODERATE on all slopes.&nbsp;</span></span></span></span></span></span></p>

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

<p><span><span><span><span><span><span>Ridgetop wind is blowing SW creating wind drifts that are being fed by last weekend’s 2 feet of powder. Wind-loading and a recently buried weak layer are the primary avalanche concerns today. These can be navigated with awareness and investigation of the snowpack. Slopes that could produce large, deep avalanches, on the other hand, are not easily identified.</span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

Events and Education Calendar.