24-25

Wind slabs, wet snow below

Date
Activity
Skiing

I skied to the bottom of the ramp this morning. There was 8-12” of heavy, mostly moist snow from yesterday. Winds were moderate to strong on the ridge and above ~7800’. Mostly cloudy.

There were some fresh, hard wind slabs on the ramp. These may exist for another day or so on high, shady slopes.

Below the new snow, the snowpack was not refrozen. There was a very thin, 1cm crust with saturated wet snow below. There were old wet slides, d2, that ran last week out of the steep terrain south of the ramp. Wet snow avalanche potential could increase quick when temperatures get hot.

Region
Bridger Range
Location (from list)
The Ramp
Observer Name
Alex Marienthal

Large recent wet loose avalanches at Bridger

Bridger Bowl
Bridger Range
Code
WL-N-R2-D2
Elevation
8000
Aspect
E
Latitude
45.80840
Longitude
-110.93000
Notes

From obs.: “Saw many recent looking wet loose avalanches on east facing slopes at Bridger. We got a good look at the debris pile from one in Z chute and it looked big enough to bury a person (D2) and had run far past the cat track into south bowl.

We encountered a lot of variation in ski penetration with ~1' of loose melt forms in places on north and east facing slopes ~8k' in elevation.”

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
2
D size
2
Problem Type
Loose Wet
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Skier triggered wet Slide off of The Nose

Bridger Bowl
Bridger Range
Code
WL-AS-R2-D1.5
Elevation
7800
Aspect
E
Latitude
45.81560
Longitude
-110.92300
Notes

From obs. “We were above the entrance to Exit Chute and triggered a slough slide that slid down one of the gullies that emptied into PK bowl. It appears to have followed an existing slide path, terminating in the top of what looked to be a significant existing avalanche runout. The slide looks pretty wide but not deep.” 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Skier
R size
2
D size
1.5
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

On May 3 We were above the entrance to Exit Chute and triggered a slough slide that slid down one of the gullies that emptied into PK bowl. It appears to have followed an existing slide path, terminating in the top of what looked to be a significant existing avalanche runout. The slide looks pretty wide but not deep. 

Bridger Range, 2025-05-06

We were above the entrance to Exit Chute and triggered a slough slide that slid down one of the gullies that emptied into PK bowl. It appears to have followed an existing slide path, terminating in the top of what looked to be a significant existing avalanche runout. The slide looks pretty wide but not deep. 

Bridger Range, 2025-05-06

Isothermal snow underneath cold pow

Date
Activity
Skiing

S1.5, winds Mod from N, OVC ~ 1400

6-8” of cold snow at Bradley’s Meadow (7,800’) but about 4-5 inches of isothermal snow and a M/F crust interface below.

if temps drop overnight, this could be a problematic layer.

winds scouring some parts of Bradley’s ridgeline and depositing 4f to 1f slabs 

 

Region
Bridger Range
Location (from list)
Bridger Bowl
Observer Name
M Standal

GNFAC Avalanche Forecast for Mon May 5, 2025

Snowpack and Avalanche Discussion

<h3><span><span><span><strong><span><span>GENERAL SPRING SNOWPACK AND TRAVEL ADVICE</span></span></strong></span></span></span></h3>

<p><span><span><span><span><span><span>NEW SNOW AND WIND LOADED SLOPES</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Spring storms are notorious for depositing heavy amounts of snow in the mountains. Even with a deep and generally stable snowpack throughout the advisory area, heavy and rapid loads of new snow will decrease stability. The main problems to look out for are avalanches breaking within the new snow, wind slabs, and loose snow avalanches. The likelihood of triggering an avalanche spikes during and immediately after snowstorms. New snow instabilities tend to stabilize quickly, but it’s a good idea to give fresh snow a day to adjust before hitting big terrain. New snow instabilities can be challenging to assess, and spring storms bond to old snow differently across aspects and elevations. Conservative terrain selection is essential during and immediately following storms. Avoid wind-loaded slopes and slopes steeper than 35 degrees for 24-48 hours after new snow and wind.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>New snow can quickly change from dry to wet on a spring day, and stability can decrease rapidly with above freezing temperatures or brief sunshine. New snow may bond well early in the morning and then easily slide later. Wet loose slides are likely during the first above freezing temperatures or sunshine immediately after a storm. Anticipate changes in snow stability as you change aspect or elevation and over the course of the day. An early start is always an advantage. Be ready to change plans or move to safer terrain at the first signs of decreasing stability.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>WET SNOW AVALANCHES</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Spring and wet snow avalanches go hand-in-hand. Above freezing temperatures, rain, and/or intense sunshine cause the snow to become wet and weak and make wet avalanches easy to trigger or release naturally. Conditions tend to become most unstable when temperatures stay above freezing for multiple days and nights in a row. Avoid steep terrain, and be aware of the potential for natural wet avalanches in steep terrain above you, if you see:</span></span></span></span></span></span></p>

<ul>
<li><span><span><span><span><span><span>Heavy rain,</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Above freezing temperatures for more than 24 hours,</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Natural wet avalanches,</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Rollerballs or pinwheels indicating a moist or wet snow surface,</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Or if you sink to your boot top in wet snow.</span></span></span></span></span></span></li>
</ul>

<p><span><span><span><span><span><span>In general, if the snow surface freezes solid overnight, the snowpack will be stable in the morning and stability will decrease through the day as snow warms up. The snow surface hardness, rate of warming, duration of sunshine, aspect and elevation determine how fast stability will decrease through the day. Be aware that sunny aspects may have a wet snow avalanche danger while shadier slopes still have a dry snow avalanche danger. Getting off of steep slopes should be considered when, or before, the above signs of instability are present. Wet snow avalanches, whether loose snow or slabs, can be powerful, destructive and very dangerous. Conservative terrain choices, starting early in the day, and careful observations can keep you safe.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>CORNICES</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Cornices along ridgelines are massive and can break under the weight of a person (photo). Prolonged above freezing temperatures and rain make them weaker and possible to break naturally. They can break off suddenly and farther back than one might expect. Cornice falls can also entrain large amounts of loose snow or trigger slab avalanches. Stay far back from the edge of ridgelines and minimize exposure to slopes directly below cornices. Regardless of whether a cornice triggers a slide or not, a falling cornice is dangerous to anyone in its path.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>DISCLAIMER</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>It does not matter if new snow falls or not, avalanches will continue to occur until the existing snowpack is mostly gone. Always assess the slope you plan to ride with diligence and safety in mind. Do not let your guard down. Travel with a partner, carry rescue gear and only expose one person at a time in avalanche terrain.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Have a safe and enjoyable spring and summer!</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Mark, Alex, Ian and Dave</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>For more spring travel advice see this&nbsp;</span></span></span></span></span></span><a href="https://www.mtavalanche.com/blog/transitions-spring-snow-avalanche-prob… our GNFAC forecaster blog.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>We will continue to share avalanche and snowpack information on our website and social media when available. </span></span></span></span></span></span><span><span><span><span><span><span>If you get out, please send us your observations no matter how brief. </span></span></span></span></span></span><span><span><span><span><span><span>Submit them via our </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_observation"><span><span><spa…; or email </span></span></span></span></span></span><a href="mailto:mtavalanche@gmail.com"><span><span><span><strong><span><u><span>…;

Slide off of The Nose

Date
Activity
Skiing

We were above the entrance to Exit Chute and triggered a slough slide that slid down one of the gullies that emptied into PK bowl. It appears to have followed an existing slide path, terminating in the top of what looked to be a significant existing avalanche runout. The slide looks pretty wide but not deep. 

Region
Bridger Range
Location (from list)
Bridger Bowl
Observer Name
Emily Hook

Large recent wet loose avalanches at Bridger

Date
Activity
Skiing

Saw many recent looking wet loose avalanches on east facing slopes at Bridger. We got a good look at the debris pile from one in Z chute and it looked big enough to bury a person (D2) and had run far past the cat track into south bowl.

We encountered a lot of variation in ski penetration with ~1' of loose melt forms in places on north and east facing slopes ~8k' in elevation.

Region
Bridger Range
Location (from list)
Bridger Bowl
Observer Name
Heather Myers

GNFAC Avalanche Forecast for Fri May 2, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Today and this weekend, the main threat is wet snow avalanches. A minimal refreeze of the snow this week combined with very warm weather the next few days will increase the odds of </span></span></span></span></span></span><span><span><span><strong><span><span>wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span>.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Often the main threat is having one start naturally above you. The good news is that the snowpack will most often give clues that it’s starting to warm up enough for wet avalanches to start happening. Areas with exposed rocks heat up the quickest and are often places where wet loose avalanches happen first. Check out this </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34962"><span><span><span><span><span><… example of a slide</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> I spotted while skiing yesterday.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Make sure to get an early start</span></span></strong></span></span></span><span><span><span><span><span><span> in the coming days and exit the mountains early. The snow should be lightly refrozen in the mornings, but will quickly break down as soon as the sun climbs into the sky by mid-morning.</span></span></span></span></span></span></p>