GNFAC Avalanche Forecast for Sat Dec 16, 2023
<p><span><span><span><span><span><span>It is possible to trigger large, dangerous avalanches today breaking beneath the last two week’s snow on weak snow in the bottom half of the snowpack. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Two natural avalanches released yesterday in closed terrain at Big Sky Resort (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/natural-avalanches-closed-terrain…;). It is unusual to get natural avalanches this long after the last snowfall without a substantial wind loading event (which we also haven’t had). One set of unusual avalanches means you should be prepared for more unusual avalanches, which means you need to be extra alert and cautious. The likelihood of triggering a large avalanche has somewhat decreased over the last few days, but recent natural avalanches clearly demonstrate that human triggered avalanches remain possible. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Yesterday, riding in the Lionhead area I saw two recent natural avalanches (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=OhmeSvFN4hI"><span><span><span><strong>…; and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29546"><span><span><span><strong><span…;). There have been many natural avalanches observed across the advisory area following the last storm and also human triggered slides (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span… and avalanche log</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=ff4qS1aF9Fs"><span><span><span><strong>…. Blackmore video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Large collapses yesterday near Cooke City are yet another indication that the weak layers are not yet dormant (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29547"><span><span><span><strong><span…;). </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The weak snow that formed during the dry spell in November is widespread in the lower snowpack and is particularly weak. It will take quite a while before we can start to trust it. Exactly how long is hard to know, but we are clearly not there yet. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Stick to lower angled slopes while waiting for conditions to improve or be very cautious if you do decide to ride steep slopes. Assess the snowpack and watch for signs that you should back off steep slopes (e.g. cracking, collapsing, recent avalanches, or poor stability test scores). </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger is rated MODERATE.</span></span></span></span></span></span></p>
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Naturals avalanches in Lionhead
Two natural avalanches observed near Lionhead on 12/15 and another two observed by a separate group on 12/14. All occurred well below the high ridgelines and likely broke several days earlier.
From obs:"We rode up Denny Creek towards Watkins Creek and spent the day below the ridge where we saw two natural avalanches. These avalanches broke 12-18" deep on weak faceted snow above a stiff crust. The first avalanche presumably happened sometime near the end of the last storm cycle (12/11), as it had a few inches of snow on the debris. The second was more recent, in the last 24-36 hours. Both were at 8500' and were on NE and E-facing slopes. "
Natural avalanche on Miller Ridge
Big Collapse in Sheep Creek
Collapsing in Sheep Creek.
From email: "Less collapsing up there yesterday than what we've been experiencing all week, but there was one BIG collapse in one of the meadows in the valley bottom (estimated 300'+ diameter). Remote triggers are still a serious concern."
Big Sky Ski Patrol reported two natural avalanches seen today (12/15) in closed terrain.
From email:
"It looks possible that they released at two different times during the day today.....It looks to be the storm snow, which was sitting on lower-density snow at the old snow interface. That interface likely had a layer of faceted snow on top of the old, crusty snow. " Photo: Big Sky Ski Patrol
Natural/Goat triggered Avalanches Big Sky
Big Sky Ski Patrol reported two natural avalanches seen today (12/15) in closed terrain.
From email on 12/16: "Further investigation of the avalanche yesterday showed goat tracks leading into the crown area of the avalanche. At the debris pile, it was obvious that a goat had taken the full ride in the slide that it triggered. There was a depression in the debris pile where the critter had come to rest at the surface, and obvious hoof prints trailing away from the debris pile, and then upslope for the long walk back up to rejoin the heard. There was no blood, and the tracks looked usual, with no obvious sign of broken leg(s). It is unknown if the goat was wearing an airbag or if it was deployed in the avalanche. It was a significant ride, 1K’ vt., 1⁄4 mile linear, likely of high speed, through 2nd Dictator transition, which was taken down to mostly bare ground."
Natural Avalanches BSSP
Big Sky Ski Patrol reported two natural avalanches, seen today (12/15) in closed terrain.
From email:
"It looks possible that they released at two different times during the day today.....It looks to be the storm snow, which was sitting on lower-density snow at the old snow interface. That interface likely had a layer of faceted snow on top of the old, crusty snow. "
Natural avalanche in Lionhead that happened near the end of the last storm cycle (12/11) Photo: GNFAC