22-23

GNFAC Avalanche Forecast for Wed Mar 22, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Today’s primary avalanche concern involves new snow that fell Monday through Tuesday morning along with wind drifts. Ian rode in Buck Ridge towards Cedar Mountain yesterday and found these 2 instabilities should be sought out and tested (</span></span></span></span></span></span><a href="https://youtu.be/dsxi7xiCRTM"><span><span><span><strong><span><u><span>…;, </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28759"><span><span><span><strong><span>…;). Dave skied into Frazier Basin in the Bridger Range on Monday and noted loose snow avalanches that were running surprisingly far on an ice crust (</span></span></span></span></span></span><a href="https://youtu.be/a1aOgLTtZio"><span><span><span><strong><span><u><span>…; </span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>and </span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28735"><span><span><span><strong><span>…;). These instabilities are easy to investigate since they are shallowly buried which is </span></span></span></span></span></span><span><span><span><span><em><span>not</span></em></span></span></span></span><span><span><span><span><span><span> the case with deep slab avalanches, a white-knuckled avalanche problem.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Large, deep avalanches are breaking on a layer of faceted, weak snow that formed in early January. All ranges have this potential, but our southern ranges especially so. Alex and Dave saw large slides in Taylor Fork (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=KJ0l4TlIh_I&amp;list=PLXu5151nmAvTi1DBS…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28725"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), I noted a big avalanche cycle in Lionhead (</span></span></span></span></span></span><a href="https://youtu.be/ncKRJpdC-iE"><span><span><span><strong><span><u><span>…;), and yesterday I investigated a large slide outside Cooke City that was triggered by a snowmobiler on Saturday (</span></span></span></span></span></span><a href="https://youtu.be/cTqk-2D4nwY"><span><span><span><strong><span><u><span>…;). Triggering these large slides requires hitting the slope in just the wrong location. The avalanche in Cooke was triggered by the 4th rider who hit a thin spot that was undetectable at the surface. Furthermore, we occasionally get a deep slide with only a light load of new snow. Deep slab avalanches are few and far between and their&nbsp; instability can’t always be detected with a snowpit. There is no outward evidence these slopes are ripe to avalanche which makes them unpredictable and scary. They are the IEDs of the snowpack.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>For today, I recommend digging and testing the upper couple feet of the snowpack. Recent snow may slide far and a wind slab could break. If you decide to get on steep slopes be fully aware that lurking deep there </span></span></span></span></span></span><span><span><span><span><em><span>may</span></em></span></span></span></span><span><span><span><span><span><span> be a dangerous layer teetering on instability that you could trigger.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Today the avalanche danger is rated MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></u></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs). </span></span></span></span></span></span></p>

<p>Today’s primary avalanche concern involves the new snow that fell Monday through Tuesday morning along with wind drifts. A secondary issue is that large, deep avalanches are breaking on a layer of faceted, weak snow that formed in early January. All ranges have this potential, but our southern ranges especially so. If you decide to get on steep slopes be fully aware that lurking deep there may be a dangerous layer teetering on instability that you could trigger. <span><span><span><span><span><span>We made a </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=O-lUMunzE1k"><span><span><span><strong>…; last week on the deep avalanches that occurred in Island Park and a snow biker sent in this </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/deep-avalanche-mt-jefferson"><spa…;. Also, we got a thorough observation of avalanche activity in Hellroaring Creek<strong> <a href="http://www.mtavalanche.com/node/28756">HERE</a></strong&gt;. </span></span></span></span></span></span></p>

<p>&nbsp;</p>

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Small wind slabs on Woody Ridge

Woody Ridge
Cooke City
Code
SS-N-R0-D1
Elevation
9700
Aspect
W
Latitude
44.97390
Longitude
-109.92400
Notes

Skied on west and east sides of Woody Ridge.  Observed a few small soft wind slab avalanches involving only new snow around the submarine. Dug a pit about a meter deep on west aspect about 9,700 feet.  HS was 290cm. No result on extended column test. Fist to 265, 4F to 245, 1f to 200 where there is a crust layer, back to 1f below that.

Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
0
D size
1
Problem Type
Wind-Drifted Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Skied on west and east sides of Woody Ridge.  Observed a few small soft wind slab avalanches involving only new snow around the submarine. Dug a pit about a meter deep on west aspect about 9,700 feet.  HS was 290cm. No result on extended column test. Fist to 265, 4F to 245, 1f to 200 where there is a crust layer, back to 1f below that.

Cooke City, 2023-03-22

New snow slide in divide basin

Divide Cirque
Northern Gallatin
Code
R1-D1.5
Elevation
10000
Aspect
N
Latitude
45.39340
Longitude
-110.96900
Notes

I went for a walk up to divide basin today and noticed a slide in the back of the basin on a high north facing slope , there was 5” of low density snow up high 

Number of slides
1
Number caught
0
Number buried
0
R size
1
D size
1.5
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Hellroaring Creek Avalanche Cycle

Hellroaring Creek
Island Park
Code
N
Latitude
44.54900
Longitude
-111.47500
Notes

Toured into the hellroaring creek 3/15-3/19. Snowing and blowing hard on 3/15 till approx 1500 hrs when wind veered to the north and skies cleared for the rest of the trip with generally cold temps and light winds. Solar aspects heating up in the day with extensive sun crusting on steeper slopes facing the south half of the compass. Observed aftermath of extensive avy cycle which prior party reported occurred approx 3/10-11 at higher elevations on Nemesis (above 8000 ft.). This is consistent with what we saw as new snow from 3/14-15 covered the debris piles at the bottom of large paths on SW face, however lower elevation steep slopes above creek at approx 7500 ft may have ran during the storm on 3/14 as less snow covered that debris. Everything observed were deep slab avalanches breaking approx 90-120 cm down. We did not investigate the weak layer. Suspect it to be the crust facet combo observed by a previous party in early March. Heavy wet snow possibly mixed with rain on 3/14-15 likely tipped the scales for these lower elevation slopes below 7500. No signs of instability of the new storm/wind slab during the five day trip, however we did get a few large collapses but these were isolated to heavily wind loaded areas in more exposed terrain. No other natural or human triggered avalanches observed during the trip. Many machiners were out testing steep slopes after the storm and we saw no signs of any human triggered avalanches. Seems higher elevation slopes that were not heavily wind loaded faired well overall. We did not measure height of snow but judging by the buried hut and barely the non-motorized boundary signs partically buried, thinking about 10 feet deep at 8000 ft. 

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Hellroaring Creek Avalanche Cycle

Hellroaring Creek
Island Park
Code
N-R3-D2.5
Latitude
44.54900
Longitude
-111.47500
Notes

Toured into the hellroaring creek 3/15-3/19. Snowing and blowing hard on 3/15 till approx 1500 hrs when wind veered to the north and skies cleared for the rest of the trip with generally cold temps and light winds. Solar aspects heating up in the day with extensive sun crusting on steeper slopes facing the south half of the compass. Observed aftermath of extensive avy cycle which prior party reported occurred approx 3/10-11 at higher elevations on Nemesis (above 8000 ft.). This is consistent with what we saw as new snow from 3/14-15 covered the debris piles at the bottom of large paths on SW face, however lower elevation steep slopes above creek at approx 7500 ft may have ran during the storm on 3/14 as less snow covered that debris. Everything observed were deep slab avalanches breaking approx 90-120 cm down. We did not investigate the weak layer. Suspect it to be the crust facet combo observed by a previous party in early March. Heavy wet snow possibly mixed with rain on 3/14-15 likely tipped the scales for these lower elevation slopes below 7500. No signs of instability of the new storm/wind slab during the five day trip, however we did get a few large collapses but these were isolated to heavily wind loaded areas in more exposed terrain. No other natural or human triggered avalanches observed during the trip. Many machiners were out testing steep slopes after the storm and we saw no signs of any human triggered avalanches. Seems higher elevation slopes that were not heavily wind loaded faired well overall. We did not measure height of snow but judging by the buried hut and barely the non-motorized boundary signs partically buried, thinking about 10 feet deep at 8000 ft. 

Number caught
0
Number buried
0
Trigger
Natural trigger
R size
3
D size
2.5
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year