Trip Planning for Southern Gallatin

as of 5:00 am
Today3″ | 5-25 N
Apr 27 0″ | 5-35 NE
Apr 26 0″ | 10-20 SE
9460′     04/28 at 8:00
23.5℉
N - 8mph
Gusts 17 mph
9000′     04/28 at 07:00
25℉
70″ Depth
Primary Problem: Wind Slab
Bottom Line: Avalanche conditions are complicated by a mix of winter and spring weather this week. Rain and snow fell on mountain snowpacks, with the most significant precipitation in the Bridger Range for the start of the week. The more new snow there is, the more likely you are to encounter avalanches and the larger their potential size. If your travel plans take you to slopes steeper than 30 degrees, assess how the new and wind-drifted snow is bonding to the old snow surface by watching for clear signs of instability, such as avalanches and shooting cracks. If rain fell on the snowpack and as temperatures warm, breaking through an unsupportable and slushy snowpack, seeing pinwheels of wet snow and small wet slides are indicators of wet snow instability.

Past 5 Days

Sat Apr 19

Moderate
Sun Apr 20

Low
Mon Apr 21

None
Fri Apr 25

None
Today

None

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Videos- Southern Gallatin

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Snowpit Profiles- Southern Gallatin

 

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Weather Stations- Southern Gallatin

Weather Forecast Southern Gallatin

Extended Forecast for

17 Miles SE Big Sky MT

  • Today

    Today: Snow likely, mainly before noon.  Cloudy, then gradually becoming mostly sunny, with a high near 39. North wind 7 to 9 mph.  Chance of precipitation is 60%. Total daytime snow accumulation of less than one inch possible.

    High: 39 °F

    Snow Likely
    then Slight
    Chance Snow

  • Tonight

    Tonight: Partly cloudy, with a low around 25. North wind around 6 mph becoming calm.

    Low: 25 °F

    Partly Cloudy

  • Tuesday

    Tuesday: A 20 percent chance of showers after noon.  Snow level rising to 8700 feet in the afternoon. Partly sunny, with a high near 49. Southwest wind 5 to 10 mph.

    High: 49 °F

    Mostly Sunny
    then Slight
    Chance
    Showers

  • Tuesday Night

    Tuesday Night: Rain showers before 8pm, then rain and snow showers between 8pm and midnight, then a chance of snow showers after midnight.  Snow level 8700 feet lowering to 7600 feet after midnight . Low around 29. West southwest wind 5 to 9 mph becoming light and variable  after midnight.  Chance of precipitation is 90%. New snow accumulation of less than a half inch possible.

    Low: 29 °F

    Rain/Snow
    then Chance
    Snow Showers

  • Wednesday

    Wednesday: A 40 percent chance of snow showers, mainly after noon.  Partly sunny, with a high near 45. North northwest wind 3 to 8 mph.  Little or no snow accumulation expected.

    High: 45 °F

    Chance Snow
    Showers

  • Wednesday Night

    Wednesday Night: Mostly clear, with a low around 27. North northwest wind 5 to 8 mph becoming calm  in the evening.

    Low: 27 °F

    Mostly Clear

  • Thursday

    Thursday: Sunny, with a high near 55. Calm wind becoming west around 6 mph in the afternoon.

    High: 55 °F

    Sunny

  • Thursday Night

    Thursday Night: Clear, with a low around 32.

    Low: 32 °F

    Clear

  • Friday

    Friday: Sunny, with a high near 60.

    High: 60 °F

    Sunny

The Last Word

Thank you for another successful season. Our success is directly related to support from our community and the Forest Service. Thanks to the readers of the forecast, everyone that sent in observations, took an avalanche class, or donated money, time or gear. We will issue conditions updates on Mondays and Fridays through April.

GENERAL SPRING SNOWPACK AND TRAVEL ADVICE

Spring weather can be highly variable and create a mix of avalanche problems. Snow conditions and stability can change drastically from day to day or hour to hour. Anticipate rapid change and plan accordingly. Abundant snowfall over the winter with more spring snow to come makes avalanches possible into summer.

NEW SNOW AND WIND LOADED SLOPES

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.

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.

WET SNOW AVALANCHES

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:

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

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. See Alex’s recent video, and this article for more spring travel advice.

CORNICES

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.

DISCLAIMER

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.

Have a safe and enjoyable spring and summer!

Mark, Alex, Ian and Dave

For more spring travel advice see this article from our GNFAC forecaster blog.

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