21-22

Propagation on Divide

Date
Activity
Skiing

I toured to Divide today, with the intent of skiing the south face in glorious sunshine and powder. A pit at the base of the south face was a surprisingly shallow 125 cm. There was a thick 4-5 cm sun crust at 75-80 cm, and I got ECTP24 on a thin (~5 mm) layer of low-density facets overlying the crust. I’m kind of surprised it held up that well, considering I noticed snow moving out of that layer as I dug the pit. On the ski out, I noticed a loose, wet slide on an steep, sun-exposed aspect. 

Region
Northern Gallatin
Location (from list)
Divide Peak
Observer Name
Sam Reinsel

GNFAC Avalanche Forecast for Thu Mar 17, 2022

Snowpack and Avalanche Discussion

<p>The snowstorm ended yesterday morning and dropped 5-8” of snow equaling .5-1”of snow water equivalent (<a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/null/?cid=nrcseprd1314…;). On Saddle Peak in the Bridger Range a cornice triggered a slide and a few other natural avalanches were noted (<a href="https://www.mtavalanche.com/node/26230"><strong><u>photos and details</u></strong></a>). Dave skied north of Bridger Bowl and made a <a href="https://youtu.be/onQg6KrJe98"><strong><u>video</u></strong></a&gt; showing wind-loading and weakness under the new snow. For the most part it has bonded to the underlying surface, but not in all cases. Yesterday, a skier triggered and was caught in a small, new snow avalanche above Lava Lake in the northern Madison Range (<a href="https://youtube.com/shorts/pRW5XvtBY6E"><strong><u>video</u></strong></…;).&nbsp;</p>

<p>Yesterday, Ian and his partner rode to Buck Ridge and did not see any avalanches, but they did get an unstable test result in their <a href="https://www.mtavalanche.com/images/22/bear-creek-profile-16-mar-2022"><… </u></strong></a>(ECTP 22). More importantly, Ian found that after months of waiting for a slab to develop, we finally have one (<a href="https://youtu.be/92V-3sb_6R0"><strong><u>video</u></strong></a&gt;). A thick slab of snow on top of a weak layer buried 1-2 feet deep is a recipe for avalanches that will not heal quickly. Although the layering is widespread throughout southwest Montana, the instability is isolated. In the absence of recent avalanches or shooting cracks, the only way to determine stability is to dig and test. On Sunday Dave highlighted this in his Beehive <a href="https://youtu.be/NTjHmlc7JHg"><strong><u>video</u></strong></a&gt;, which was the same day a skier triggered a 500’ wide slide next to Big Sky Ski Resort (<a href="https://youtu.be/f6wLR3tLNa8"><strong><u>video</u></strong></a&gt;). Ian and I also noted the sporadic nature of the instability during Tuesday’s tour into Mt. Blackmore (<a href="https://youtu.be/92V-3sb_6R0"><strong><u>video</u></strong></a&gt;).</p>

<p>Avalanches are possible today and even small slides can be deadly. In February, a snowmobiler was killed in Lionhead in a slide 75’ wide and yesterday a skier was caught in an avalanche that looked to be 25’ wide. On Saturday, a snowmobiler in southern Wyoming died in a small slide as well (<a href="https://youtu.be/chiQ_Bw0M9Y"><strong><u>accident investigation video</u></strong></a>).&nbsp;</p>

<p>Stay clear of wind-loaded terrain at the ridgelines and be prepared to investigate the snowpack.&nbsp; For today the avalanche danger is rated MODERATE on all slopes.</p>

<p>&nbsp;</p>

<p>Cooke City has gotten at least&nbsp;20” of snow since Saturday along with many avalanches (<a href="https://www.mtavalanche.com/avalanche-activity"><strong><u>avalanche list</u></strong></a>). The slides are breaking on a weak layer of facets 1-2 feet under the surface which remains unstable. Alex rode and skied and noted this layer in his two videos from <a href="https://youtu.be/beIj2Ar5_yk"><strong><u>Saturday</u></strong></a&gt; and <a href="https://youtu.be/f6wLR3tLNa8"><strong><u>Monday</u></strong></a&gt;. Only expose one person at a time to avalanche terrain and stay away from steep slopes if you get cracking, collapsing or poor test scores. Triggering avalanches remains possible and the danger is rated MODERATE on all slopes.</p>

<p>*Today’s forecast references 8 mtavalanche videos. Instead of clicking on them individually you can watch them all on our <a href="https://www.youtube.com/playlist?list=PLXu5151nmAvT1nrM2joYgS2bKP7SdHGk… Playlist</u></strong></a>.&nbsp;</p>

<p>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).</p>

<p>&nbsp;</p>

Skier triggered and caught in slide above Lava Lake

Lava Lake
Northern Madison
Code
SS-ASu-R1-D1.5
Elevation
8000
Aspect
N
Latitude
45.37650
Longitude
-111.24600
Notes

Skier triggered slide on north-facing slopes above Lava Lake. Skier was caught, but not buried.

Video: https://youtube.com/shorts/pRW5XvtBY6E 

Number of slides
1
Number caught
1
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
1
D size
1.5
Problem Type
New Snow
Slab Thickness
6.0 inches
Vertical Fall
50ft
Slab Width
25.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

 "...cornice triggered slide on saddle today. Broke a couple of feet deep, and I couldn’t get too close to the crown but it seemed to have initially broken in the new snow and then stepped down to a PWL below the recent crust...propagated maybe 130ft wide and ran all the way over the saddle cliff to the flats." Photo J. Keogh

Bridger Range, 2022-03-17