22-23

Instability on Republic Pass

Date
Activity
Skiing

We toured out to republic pass. Saw mutliple small natural wind slab releases. We dug a pit on Republic Pass around 9800 ft on a north facing slope with lots of wind, got an ECTP 26 @ 30cm down from the snow surface on a very thin layer of facets. We only dug a ~5ft deep pit but found very stiff and solid snow throughout the snow pit (1 finger to pencil stiffness). Very little fresh snow was on the surface due to the wind ripping through the pass. It snowed for the whole first half of the day, lots of wind but only about 1cm of accumulation.

Region
Cooke City
Location (from list)
Republic Mountain

Some instability south of Quake Lake

Date
Activity
Skiing

We skied three runs south of Quake Lake, up to 9400 ft. Most snow was crusty until it warmed up, but we found some powder in the shade and on north and east aspects, especially up high.  Dug a pit at 8400 ft, N aspect, 32-degree slope.  Result was ECTN-20 at 25 cm, and ECTN-22 at 35 cm.  Sheared fairly cleanly.  We were halfway up the avalanche chute at that point, so skied down with no incidents and skied two other tree runs.

Region
Lionhead Range
Location (from list)
Quake Lake
Observer Name
Mark Reinsel

Wet slide over highway at quake lake

Quake Lake
Southern Madison
Code
WL-N-R3-D2.5
Elevation
7500
Aspect
S
Latitude
44.85340
Longitude
-111.40000
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
3
D size
2.5
Problem Type
Wet Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Emigrant observations

Date
Activity
Snowboarding

We toured into Emigrants southeast bowl on Saturday. We found thin and reactive wind slabs on north facing slopes. Our ECT on a north face gave us stable results below the wind slab layer. It was the second day in a row of high temperatures and full sun but there was very little wet slide activity in this zone. We observed multiple old crowns in the surrounding mountains that looked to be a few feet thick. They were possibly breaking on a crust layer we found about 2 feet deep in our pit. 

Region
Out of Advisory Area
Observer Name
Gage

GNFAC Avalanche Forecast for Sat Apr 8, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Warmer spring weather brings a diverse list of avalanche concerns this weekend. Wind slabs and persistent weak layers remain reactive, and wet loose avalanches are possible.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>A person could trigger large to very large avalanches that break below the snow that fell last weekend, or several feet deep on weak layers that were buried in January. On Thursday, near Cooke City a skier triggered a wind slab on Scotch Bonnet Mountain (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28986"><span><span><span><strong><span… and photo</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), and in the northern Gallatin Range a snowmobiler triggered a 1 foot deep wind slab (</span></span></span></span></span></span><a href="http://www.mtavalanche.com/node/28998"><span><span><span><strong><span>… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Slides also broke 1-3 ft deep on wind-loaded slopes near Cooke City and in the Bridger Range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28994"><span><span><span><strong><span… details 1</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span>, </span></span></strong></span></span></span><a href="https://www.mtavalanche.com/node/29005"><span><span><span><strong><span… details 2</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>,</span></span></span></span></span></span><span><span><span><strong><span><span> </span></span></strong></span></span></span><a href="https://www.mtavalanche.com/node/28983"><span><span><span><strong><span… Peak details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Assess for recent wind-loading and dig down to investigate the top couple feet of the snowpack for instability before riding steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Huge deep slab avalanches have occurred since late February, and we’ve had reports of many monster slides that broke after last weekend’s snow. Yesterday, skiers reported recent deep slabs in the Northern Madison (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29012"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>) and Southern Gallatin Ranges (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29004"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). We also know of big avalanches that occurred last weekend near </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28949"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28924"><span><span><span><strong><span… City</span></span></u></span></strong></span></span></span></a>,<span><span><span><span><span><span> and in the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/28900"><span><span><span><strong><span… Range</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>. These deep instabilities are difficult to test for, so your best bet is to avoid steep slopes entirely. If you accept the low likelihood, high consequence risk and venture into steep terrain, hedge your bets by choosing terrain with less wind-loading and without the consequences of trees or cliffs.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Last night’s below freezing temperatures allowed yesterday’s wet snow surface to refreeze. Wet snow avalanches will become more likely as the snow surface softens and loses strength later in the day, especially on sunny slopes. A few may release naturally around rocky outcrops on slopes that face the sun. Anticipate wet loose slides to occur when the upper few inches of the snowpack become soft and wet. Be alert for quickly changing conditions and plan to be off and out from underneath steep, sunny slopes when you notice the snow surface starting to melt.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>A wide range of avalanche concerns make human triggered avalanches possible, and today the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Our last daily forecast will be this Sunday, April 9. We will issue weather and snowpack updates every Monday and Friday through April. Please share avalanche, snowpack or weather observations via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).</span></span></span></span></span></span></p>

<p>Warmer spring weather brings a diverse list of avalanche concerns this weekend. Wind slabs and persistent weak layers remain reactive, and wet loose avalanches are possible. Assess for recent wind-loading and dig down to investigate the top couple feet of the snowpack for instability. Deeper instabilities are difficult to test for, so your best bet is to avoid steep slopes entirely. If you accept the low likelihood, high consequence risk and venture into steep terrain, hedge your bets by choosing terrain with less wind-loading and without the consequences of trees or cliffs. Be alert for quickly changing conditions and plan to be off and out from underneath steep, sunny slopes when you notice the snow surface starting to melt.</p>

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Wet loose and slab avalanches North of Cooke

COOKE CITY
Cooke City
Code
N
Latitude
45.02020
Longitude
-109.93800
Notes

Lots of naturals and maybe a rider triggered avalanche seen today. Steep solar aspects had lots of wet loose activity and small cornice/pillow fall. 

Number of slides
4
Number caught
0
Number buried
0
Trigger
Natural trigger
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year