24-25
GNFAC Avalanche Forecast for Fri Jan 24, 2025
<p><span><span><span><span><span><span>The primary avalanche concern today is avalanches breaking in wind drifts. </span></span></span></span></span></span><span><span><span><strong><span><span>Wind Slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> could break in wind drifts that formed earlier in the week, or with a bit of snow falling today and adding to the snow available to blow around, 1-2 ft deep avalanches could break in freshly drifted snow. Yesterday, skiers in Cooke City had wind slabs crack and saw lots of wind transport up high (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33825"><span><span><span><span><span><…;). Mark and Dave found small facets (a weak layer) yesterday about 4” below the surface on Lionhead Ridge, this could make new drifts more reactive and avalanches a little bigger (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33821"><span><span><span><span><span><…;). Seek out wind-sheltered slopes to avoid this problem.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Larger </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>breaking on old weak layers also remain possible. We haven’t seen slides on these weak layers recently, but we don’t quite trust them yet. There were several large avalanches early last week near Cooke City (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33528"><span><span><span><span><span><…; and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33544"><span><span><span><span><span><…;), one in the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33584"><span><span><span><span><span><… Madison Range</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, and one </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33790"><span><span><span><span><span><… sign of instability last Sunday near Cabin Creek</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>. If you get unlucky and trigger one of these slides - it’ll be big, destructive and deadly. This possibility should motivate you to tone down terrain choices and stay off the biggest, steepest, rockiest slopes.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Human triggered avalanches remain possible and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>
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<p><span><span><span><strong><span><span>Wind Slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are also the main concern in the mountains near Bozeman, Big Sky, and Island Park. Active wind transport was noted yesterday on the high peaks and winds picked up more overnight (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33824"><span><span><span><span><span><…;). Skiers in Hyalite yesterday saw a thin, recent wind slab (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33827"><span><span><span><span><span><…;). More of the same is possible today and they could break deeper as well. The big volume of low density snow that fell in the Bridgers earlier in the week finally got blown around last night, so this is where I’d expect to find the deepest and most reactive wind slabs today. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>As snow falls and drifts today, be alert for fresh wind slab forming. Steering around wind drifts will dramatically reduce the risk of triggering a slide today. Look for visual clues of wind drifting, feel for a stiffening surface snow under your feet or sled, and watch for cracks shooting out in front of you as a clear sign that you’ve found an unstable wind drift and should retreat to lower angled terrain. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger is MODERATE on wind loaded slopes and LOW on all other slopes.</span></span></span></span></span></span></p>
KING AND QUEEN OF THE RIDGE
Do you like to hike? Do you like to ski/ride? Then the King & Queen of the Ridge on 2/1 is for you. Hike, ride and raise money for the Friends of the Avalanche Center at Bridger Bowl this year! Join this fun event to promote and support avalanche safety and awareness! Fundraising prizes for the top 5 individuals who raise over $500.
Thin wind slab in Hyalite
Cornice fall and thin wind slab
I toured up to the Divide Cirque today, and found some quality riding on SE, E, and NE aspects.
I saw evidence of a recent car-sized cornice fall on an E aspect. The resulting dry loose ran far, but saw no crown or evidence of a deeper avalanche.
Also noted a recent natural wind slab avalanche below ridgeline on a SE aspect at 9800’. It was around 60’ wide and ranged from 2-6” deep.
The clouds came out just in time, before the sun began to have any effect on solar aspects. Saw active wind transport over by Hyalite Peak, but it wasn’t as bad over in Divide.
Republic Mountain Obs
Isolated shooting cracks and windslabs above treeline south of Cooke City today. Strong winds from the west. Lots of wind transport going on up high. The vis was good this morning and I could see far for the first time in a while. I saw no new avalanches.
Beehive Basin Obs
From email: "Skies were clear at 8am, but clouds rolled in quickly and we had S-1 snowfall starting at 1pm. Winds were L in the basin and L-M at ridge tops out of the W-NW. Moderate snow transport on high elevation peaks. West aspects near ridgetops were scoured, as they usually are. We found a 2-3cm thick MF crust under 5-10cm of new snow on E, W, and S aspects near ridgetops and in the basin. No cr, co.
Students dug pits on E-SE aspects at 9200', as well as on E and W aspects near the Prayer Flags. HS ranged from 100-145cm. Two of ten pits had propagation. ECTP1 on small facets above the MF crust and under a wind slab. ECTP30 on 2mm facets 30cm up from the ground. Hand pits had planar results below the MF crust where it was capped by a wind slab."
1 meter deep snowpack showing the obvious facets in the bottom third
Forecast link: GNFAC Avalanche Forecast for Fri Jan 24, 2025
Lionhead Jan 23
We went to Lionhead seeking some of the thinnest and weakest snow. We found relatively thin snow - the snowpack was mostly a 1 meter deep (3.2 ft). It was supportive for sleds and you could walk on top with about 6-8 out of every 10 steps not punching through to the ground. This is because there is a very cohesive slab on top of the early December facets.
What surprised us was how stubborn that weak layer was in our tests. We dug in 4 different places on E, E, E, and NW aspects between 8000 and 9200 feet. ECT's either wouldn't even break or would propagate on the weak layer after mid to high 20's for taps.
We observed some new facets near the snow surface that formed last weekend during very cold weather. On Lionhead Ridge we found these facets capped by a hard but thin (~4 inch thick) wind slab.
Summary
- The early December faceted layer seems mostly dormant for now.
- Wind slabs are the main problem and they will be extra sensitive as more snow comes Friday providing winds more ammo to make the wind slabs deeper. Because these wind slabs may be resting on facets, they could stay a problem for sometime.
- We did not get a chance to map how widespread or isolated this wind slab/facet combo is.