21-22

GNFAC Avalanche Forecast for Sat Mar 12, 2022

Snowpack and Avalanche Discussion

<p>Avalanches can break on weak layers buried around 2 ft deep or in freshly formed wind drifts. Watch for cracking drifts and keep the possibility of triggering a much larger slide in mind if you’re thinking about riding in steep terrain (<a href="https://www.youtube.com/watch?v=BGiz4qC7pQg"><u>Scotch Bonnet avalanche video</u></a>). An avalanche of newly wind drifted snow could easily pile up deep enough to bury you in a gully or push you into trees and it could also trigger a slide on those deeper weak layers. Human triggered avalanches are possible and the avalanche danger is MODERATE today.</p>

<p>Avalanches can be triggered today on slopes loaded by the strong west winds or those that are baking in the sun as temperatures rise above freezing. Especially on slopes with a firm crust underneath the new snow, loose snow slides could run a long way and entrain a surprising volume of snow. The snow surface becoming sticky, rollerballs, or fresh point releases are all clear signs that you could trigger a loose snow avalanche. Very strong winds have loaded slopes at all elevations. Slides could break in just the new snow or on weak layers that formed during our long January/February dry spell (<a href="https://www.mtavalanche.com/images/22/skier-triggered-windslab-hyalite"…;, <a href="https://www.mtavalanche.com/images/22/wind-slab-mt-blackmore"><strong><…;, <a href="https://www.youtube.com/watch?v=ulXRgmKlrRw"><strong><u>Lionhead video</u></strong></a>). Be on the lookout for fresh wind drifts and stay off steep slopes if they’re cracking. The avalanche danger is rated MODERATE today.</p>

<p>Temperatures staying a bit cooler and somewhat lighter winds than in northern areas means you’re unlikely to trigger large avalanches today. Keep the same concerns in mind as in other parts of the advisory area - unstable wind drifts and wet loose slides. The key difference is that you’re less likely to find these concerns and any resulting avalanche will likely be smaller. Stay heads up in places where a small slide would have big consequences. The avalanche danger is LOW.</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>

Upcoming Education Opportunities

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events.

Every Saturday near Cooke City, 10 a.m.-3 p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.

 

Mt. Ellis

Date
Activity
Skiing

No big surprises. Sun early gave way to overcast skies by ~2pm. Moderate west wind really only felt in the meadow and right at the ridgeline. At the ridgeline, ~8" of low density snow from recent storm cycle not bonded well to melt/freeze crust from last weekend. Easily slides off in hand shear tests, but has not yet formed a cohesive slab. I saw little to no evidence of significant wind slab formation. 

I dug near the summit and found 2 melt/freeze layers with weaker snow throughout. Consistent with recent forecasts, these weak layers were unreactive, producing ECT-X result. Snowpit attached. 

@ lower elevations, snow was generally faceted, thinner and weak. 2-3 inches of new snow in the meadow area. 

Obviously everything is likely to change in the next few days with warm weather in the forecast. 

Region
Bridger Range
Location (from list)
Mt Ellis
Observer Name
Chris Pierce

GNFAC Avalanche Forecast for Fri Mar 11, 2022

Snowpack and Avalanche Discussion

<p>Avalanches breaking in wind drifts are the primary concern today. Yesterday, several groups of skiers on Mt. Blackmore found touchy wind slabs that were easily triggered (<a href="https://www.mtavalanche.com/images/22/skier-triggered-windslab-hyalite"…;, <a href="https://www.mtavalanche.com/images/22/wind-slab-mt-blackmore"><strong><…;). These slides broke around a foot deep and were only 10-20 ft wide, but ran up to 800 vertical feet. In many other areas winds had been calm since it snowed earlier in the week, but picked up to effective drifting speeds yesterday afternoon. Be on the lookout for fresh wind drifts where you could trigger similar slides. Cracks shooting out in front of your skis or snowmobile are clear signs that you’ve found an unstable drift.&nbsp;</p>

<p>On many slopes, underneath the new snow there is a weak layer that formed during our long January/February dry spell (<a href="https://www.youtube.com/watch?v=ulXRgmKlrRw"><strong><u>Lionhead video</u></strong></a>). Yesterday in the Taylor Fork, Alex and I found that on some sunny slopes there is a crust on top of this weak layer, but the weak layer is still there (<a href="https://www.youtube.com/watch?v=5o-XoWhmTcU"><strong><u>video</u></stro…;). Avalanches on this weak layer will be wider, slightly deeper, and could break further above you on the slope, making them more dangerous. In places where it snowed less earlier this week and the wind hasn’t drifted the new snow, you will find many slopes where there still isn’t a substantial slab on top of this weak layer. Look out for cohesive slabs above this weak layer and carefully test the snowpack or avoid steep slopes if you find them. Triggering avalanches is possible and the avalanche danger is rated MODERATE today.</p>

<p>Near Cooke City, there are weak layers buried around 2 ft deep that you could trigger a slide on. The last reported slide on this weak layer was triggered by a snowmobiler last Sunday on the north side of Scotch Bonnet (<a href="https://youtu.be/BGiz4qC7pQg"><strong><u>video</u></strong></a&gt;). The problematic weak layer-slab combination is widespread around Cooke City. It is getting harder to trigger one of these slides, but it remains possible (<a href="https://www.youtube.com/watch?v=z2GJqshr8_M"><strong><u>video</u></stro…;). This sort of weak layer takes a long time to heal, so continue to be patient. Keep carefully considering the possibility of triggering a large slide before riding steep slopes. The avalanche danger is MODERATE today.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

<p>&nbsp;</p>

Upcoming Education Opportunities

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events.

Every Saturday near Cooke City, 10 a.m.-3 p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.

Skier triggered windslabs in Hyalite

Mt Blackmore
Northern Gallatin
Code
SS-ASu-R1-D1
Latitude
45.44440
Longitude
-111.00400
Notes

From obs (3/10/22): "Today we triggered a small pocket of wind loaded snow while ascending (bootpacking) the East ridge of Blackmore. The convexity broke about 1 foot down and propagated about 10 feet wide. It ran the entire distance of the East face ~800’. "

A second report noted additional skier triggered wind slabs on Mt. Blackmore.

Number of slides
4
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
u-An unintentional release
R size
1
D size
1
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

From obs (3/10/22) : "Today we triggered a small pocket of wind loaded snow while ascending (bootpacking) the East ridge of Blackmore. The convexity broke about 1 foot down and propagated about 10 feet wide. It ran the entire distance of the East face ~800’."

Photo: C. Firer

Northern Gallatin, 2022-03-11