22-23
Measured 3.6” SWE in storm in Bridgers
Date
Activity
Skiing
At 5pm on 4/20/23 I dug a quick snowpit to look at the storm snow o the Bridger Ridge. at 8,400’ there was 36” of settled snow equal to 3.6” SWE from the last two days. Total depth was 311cm (~10’ 3”).
No cracking or easy triggered loose snow on small test slopes. Surface was getting more slab-like or cohesive. In general the snow was more stable than yesterday, but there was a ton of snow so still potential for big avalanches. Probably less frequent than the recent dry loose snow activity, but potential for larger slab avalanches or wet avalanches.
Stability of the new snow could become worse if wind increases and drifts the snow into dense slabs, or when warm temperatures and sunshine arrive later in the weekend and make the snow wet and weak.
Region
Bridger Range
Location (from list)
Bridger Bowl
Observer Name
Alex Marienthal
Quick to stabilize Fairy Lake
Date
Activity
Snowmobiling
Spent the day choking on DEEP snow in the meadows around Fairy Lake. Light to mod. showers all day with a brief lull around 330 which allowed a window of visibility into the upper elevation terrain: No slab avalanches observed which surprised me (hence the obs.), very minimal loose snow moving despite the impressive SWE totals. Some wind texture at upper elevations but the new snow appears to be settling out quickly in typical April fashion.
Region
Bridger Range
Location (from list)
Fairy Lake
Observer Name
andrew newman
Deep snow in Beehive, some sluffing
Date
Activity
Snowboarding
20-36" of low to medium density snow in beehive, bear, and middle basins. Moderate west winds and overcast skies. It snowed lightly all day and the sun never came out.
We skied south, east, and west aspects. Snow was mostly right side up and was unconsolidated. Sluffs were running on steeper terrain, but other than that, we didn't experience any reactivity or signs of unstable snow.
Region
Northern Madison
Location (from list)
Middle Basin
Observer Name
Josh Lipkowitz
GNFAC Avalanche Forecast for Thu Apr 20, 2023
Snowpack and Avalanche Discussion
<p><span><span><span><span><span><span>This snowpack update is one day early due to yesterday’s snowfall creating very dangerous avalanche conditions in the Bridger Range. The Bridgers received 32-40” of snow equal to 2.5” of snow water equivalent (SWE) in less than 24 hours. Yesterday, as snow rapidly stacked up, skiers at Bridger Bowl noted easily triggered loose snow avalanches which entrained large volumes of snow by early afternoon (</span></span></span></span></span></span><a href="http://www.mtavalanche.com/images/23/avalanche-apron"><span><span><span… on Apron</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=Q4ZnhKX3TGE"><span><span><span><strong>… 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://www.youtube.com/watch?v=gYmr-V73OD8"><span><span><span><strong>… 2</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Similar avalanches of new snow will be easy to trigger today through the weekend. Slides may become larger and could break naturally as more snow falls and where wind is drifting new snow into denser slabs. The same hazards exist in other mountain ranges, but avalanches will be smaller, though still dangerous, due to less new snow.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>During spring, stability of new snow tends to be more variable and unpredictable than what we are used to most of winter, due to factors like firm crusts below or large temperature changes during the day. Before considering travel on any steep slopes, carefully assess the stability of the new snow. When stability assessment is tricky or uncertain, choose conservative terrain. Ride or ski slopes that are less than 30 degrees steep, or non-wind loaded and without consequences of hitting trees or rocks.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>When the sun shines and temperatures rise, the new snow will get wet and more unstable, and large avalanches will be easy to trigger or could run naturally. This isn’t expected until later in the weekend, but stability can change rapidly during spring. If you notice the snow surface becoming moist or wet, be ready to change plans, or plan to be away from steep terrain when it receives direct sun and later in the day when temperatures are above freezing. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Other problems to be aware of are large cornices along ridgelines and deeper persistent weak layers. Both are less likely than new snow avalanches this weekend, but they do exist. When temperatures warm, cornices could break easier. Give cornices a wide berth along ridgelines and avoid slopes below them (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/cornice-fall-mount-abundance"><sp…. Abundance</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/giant-cornice-collapse-north-madi… Madison Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Avalanches breaking deeper in the snowpack are unlikely where a thick crust formed during last week’s extended warm up. However, higher elevation shady slopes might still have this problem, where there is not a thick crust below the recent 1-3 feet of snow. (Deep slabs Northern Madison Range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29012"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29119"><span><span><span><strong><span…;), </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29004"><span><span><span><strong><span… Gallatin Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28949"><span><span><span><strong><span… Area</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://www.mtavalanche.com/node/28900"><span><span><span><strong><span… Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>We will issue our next spring snowpack and weather update on Monday, and we will continue to share relevant avalanche and snowpack information on our website and social media. If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</span></span></span></span></span></span></p>
Info and Reminders
We are updating our avalanche and weather log daily and posting relevant changes to the avalanche conditions so you can
New snow avalanches at Bridger
Bridger Bowl
Bridger Range
Code
L-ASc-R2-D2-S
Elevation
8000
Aspect Range
E,NE,SE
Latitude
45.81560
Longitude
-110.92300
Notes
By early afternoon on 4/19/23 the three feet of new snow was easily avalanching and running long distances with large volume. Video from Test Face/Lower Nose.
The new snow slid easily on steep slopes, mostly dry loose avalanches, but by the afternoon these were entraining large, dangerous volumes of snow. Video is from this morning, small test slope at 6,300', north facing. Now there is a lot more snow, and much more at higher elevations. It snowed heavily all day. Wind was moderate on the ridge, calm with moderate gusts below the ridge, and moderate/gusty on the lower half of the mountain.
Large avalanches of new snow will be easy to trigger for the next few days, and large natural avalanches are possible. Conditions will continue to become more dangerous if heavy snow continues.
Number caught
0
Number buried
0
Avalanche Type
Loose-snow avalanche
Trigger
Skier
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
2
D size
2
Bed Surface
S - Avalanche released within new snow
Problem Type
New Snow
Attached Videos
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
Large new snow avalanches at Bridger
Date
Activity
Skiing
By early afternoon on 4/19/23 the three feet of new snow was easily avalanching and running long distances with large volume. Video from Test Face/Lower Nose.
Region
Bridger Range