GNFAC Avalanche Forecast for Wed Jan 22, 2025
<p>Wind slab avalanches will be the most likely problem today after yesterday's strong winds as well as strong winds from late last week. You'll surely find them under upper elevation ridgelines and cornices, but look for them at lower elevations where winds cross load gullies, subridges, and other terrain features. Yesterday in Sheep Creek near Cooke City, guides spotted a 200 ft wide wind slab that had released naturally. It may be harder to identify these areas with a few inches of new snow camouflaging the fresh wind slabs.</p>
<p>This wind loading will bump up the possibility of triggering a much larger persistent slab avalanche breaking on old weak layers of facets about 1-2 feet above the ground. These larger avalanches have become much less frequent with three spotted just over a week ago, and snowmobiler triggering deep shooting cracks on Sunday in the southern Madison Range.</p>
<p>Today in the southern Madison and Gallatin Ranges, in the Lionhead area near West Yellowstone, and in the mountains near Cooke City; the avalanche danger is MODERATE.</p>
<p>Wind slab avalanches are the main problem as well in the mountains near Bozeman, Big Sky and Island Park. Dave describes this problem well in his video from yesterday in Hyalite Canyon posted to YouTube. Fresh snow today will make it harder to identify these fresh wind slabs, but use your best judgement to estimate where winds deposited snow yesterday and avoid those slopes.</p>
<p>Persistent slab avalanches are unlikely, and old weak layers have gained strength on most slopes where the snowpack is over about 5 feet deep. Today in the Bridger Range, in the northern Gallatin and Madison Ranges, and the Island Park area, the avalanche danger is MODERATE on wind loaded slopes which are more widespread than not. Slopes sheltered from the wind without any recent wind loading have a LOW danger.</p>
Today, we traveled into the Maid of the Mist basin and up and along the Palace Butte ridgeline. Although temperatures have warmed up significantly since the weekend, strong winds kept conditions frigid. Winds blew plumes of snow off the high peaks and at ridgelines, gusting 50-60 mph. Photo: GNFAC
Winds blew plumes of snow off the high peaks and at ridgelines, gusting 50-60 mph. Photo: GNFAC
Winds blew plumes of snow off the high peaks and at ridgelines, gusting 50-60 mph. Photo: GNFAC
Wind Loaded Slopes in Hyalite
Today, we traveled into the Maid of the Mist basin and up and along the Palace Butte ridgeline. Although temperatures have warmed up significantly since the weekend, strong winds kept conditions frigid. Winds blew plumes of snow off the high peaks and at ridgelines, gusting 50-60 mph. Even at low to mid elevations, spindrift was blowing off of cliffs, snow was blowing out of trees, and the surface of the snowpack had been affected by wind. We found stiff, hardened surfaces and sastrugi starting around 8800', nearly 1000' lower than the tops of the surrounding ridgelines.
Most of the high elevation snow has been transported already. Up high, snow surfaces are hardened and we were mindful of wind slabs that have formed in the last few days.
On a north facing aspect at 8800' we got an ECTP 22 in our pit test on a wind slab over softer snow. We also dug on a south facing aspect and found new snow on top of a melt-freeze crust and small faceted grains. This crust likely formed during the warm temperatures before the cold spell last Thursday (1/16).
We heard one collapse on a heavily wind-loaded pillow of drifted snow, but beyond that, the only other sign of current instability was the active wind loading itself.
We chose to avoid traveling on slopes steeper than 30 degrees that had signs of wind affected snow (textured snow surfaces, stiffening of surfaces, and obvious wind pillows). Slopes that had not been affected by wind held the safest and highest quality riding.
Wind slab avalanche on E Henderson North of the large slide path close to Fisher Pk. R1 D2,1-2' deep, 200' wide. It broke aprx 200' below the summit mid slope. It looked like it broke on the 19th. Photo: BPG
GNFAC Avalanche Forecast for Tue Jan 21, 2025
<p>Human-triggered avalanches failing on weak layers of faceted snow in the lowest 1-2 feet of the snowpack are possible in the mountains around West Yellowstone and Cooke City and in the Southern Gallatin and Southern Madison Ranges.</p>
<p>Large <strong>persistent slab avalanches</strong> are becoming less likely and the most recent known slides occurred one week ago (<a href="https://www.mtavalanche.com/node/33584"><strong><span>Red Mountain</span></strong></a>, <a href="https://www.mtavalanche.com/node/33544"><strong><span>Woody Ridge 1</span></strong></a>, <a href="https://www.mtavalanche.com/node/33528"><strong><span>Woody Ridge 2</span></strong></a>). However, a rider near Cabin Creek sent in a video of knee-deep, shooting cracks propagating across the slope on Sunday (<a href="https://www.mtavalanche.com/node/33790"><strong><span>photos</span></st…;). Do not ignore these signs of persistent slab instability. Avalanches are most likely on slopes with significant variations in snow depth where a skier or rider impacts weak layers that fail in shallow areas around rocks or wind-scoured terrain and propagate across a slope. Conversely, avalanches are less likely on slopes with a uniformly deep snowpack.</p>
<p><strong>Wind slab avalanches</strong> are possible where snow drifts onto steep slopes. Yesterday, riders in Cooke City noted a natural avalanche within the wind-drifted snow on Henderson Mountain that broke up to two feet deep (<a href="https://www.mtavalanche.com/node/33806"><strong><span>details</span></s…;).</p>
<p><strong>If you consider traveling on slopes steeper than 30 degrees</strong>, choose non-wind-loaded terrain with relatively deep and consistent snow cover. Follow safe travel practices, ensuring all party members carry a beacon, shovel, and probe and only expose one person at a time to hazardous slopes.</p>
<p><span>The avalanche danger is MODERATE.</span></p>
<p>In the mountains near Bozeman, Big Sky and Island Park, <strong>wind slab avalanches</strong> are possible on steep slopes with recent drifts of wind-loaded snow. Avalanches are unlikely in non-wind-loaded terrain.</p>
<p>Strong winds are drifting snow into slabs several inches to a few feet thick. On Sunday, Alex and Haylee toured north of Bridger Bowl, triggering thin wind slabs on small test slopes (<a href="https://www.youtube.com/watch?v=19A0eFtksEQ"><strong><span>video</span>…;, </strong><a href="https://www.mtavalanche.com/node/33779"><strong><span>observation</span…;). Local ski patrols triggered avalanches on wind-loaded slopes during frosty avalanche mitigation work, and backcountry travelers reported “reactive wind slabs up to 30 inches deep” in the Bridger Range (<a href="https://www.mtavalanche.com/node/33804"><strong><span>observations 1</span></strong></a><strong>, </strong><a href="https://www.mtavalanche.com/node/33803"><strong><span>2</span></strong>…;). Use visual clues of drifting and signs of instability, such as cracking or a stiffening of the snow surface, to identify and avoid problem areas (<a href="https://www.mtavalanche.com/images/25/shooting-crack-jefferson-17-jan-2…;, <a href="https://www.mtavalanche.com/images/25/cracking-shallow-wind-drift"><str…;). Even a small wind slab may have significant consequences in steep or extreme terrain.</p>
<p><strong>Persistent Slab Avalanches</strong> breaking on weak layers near the bottom of the snowpack are unlikely. However, isolated areas of instability exist. On Sunday, skiers found a poor snowpack structure and experienced multiple collapses in a shallow snowpack near Fairy Lake (<a href="https://www.mtavalanche.com/node/33788"><strong><span>observation</span…;).</p>
<p><span>While following safe travel practices, seek out slopes <em>sheltered from the effects of the wind</em> with a <em>uniformly deep</em> snowpack, as these will be the safest. The avalanche danger is MODERATE on wind-loaded slopes and LOW on other slopes.</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. No racing is necessary to compete for the fundraising prizes.
Weather and Avalanche Log for Tue Jan 21, 2025
Temps Range from -11 F LH Ridge to +13 F in Hyalite
Wind Slab on E Henderson
Wind slab avalanche on E Henderson North of the large slide path close to Fisher Pk. R1 D2,1-2' deep, 200' wide. It broke aprx 200' below the summit mid slope. Phone was too cold to take photos. It looks like it broke on the 19th. Wind slabs 5-10" deep were easy to trigger on test slopes North o Lulu pass. Active loading today on upper elevation SW-SE aspects. Multiple ECTX test results on S aspects at 8600' over the weekend.
Wind Slab on E Henderson
Wind slab avalanche on E Henderson North of the large slide path close to Fisher Pk. R1 D2,1-2' deep, 200' wide. It broke aprx 200' below the summit mid slope. Phone was too cold to take photos. It looks like it broke on the 19th. Wind slabs 5-10" deep were easy to trigger on test slopes North o Lulu pass. Active loading today on upper elevation SW-SE aspects. Multiple ECTX test results on S aspects at 8600' over the weekend.