Regional Conditions for Southern Gallatin

as of 5:00 am
Today2" | N/A
Feb 21 1" | NA
Feb 20 0" | NA
9460′     02/22 at 22:16
2.3℉
SE - 8mph
Gusts 15mph
9000′   02/22 at 23:00
7℉
Depth
Bottom Line: Dense wind slabs that formed over the past few days remain a concern. These thick, cohesive slabs rest over lower density snow, which is creating an unstable structure. Wind slabs could fail under the weight of a skier or rider and pose the most significant threat in steep-high consequence terrain.

Past 5 Days

Sun Feb 18

Considerable
Mon Feb 19

Moderate
Tue Feb 20

Moderate
Wed Feb 21

Moderate
Today

Moderate

Photos- Southern Gallatin

  • Skiers up Mt Blackmore triggered small wind slabs near the ridgelines. These slides were small, but could produce high consequences if triggered in steep terrain. Photo: C. Ronemus 

  • This picture was taken on Monday, February 19, at Lionhead on an east-facing slope. The wind slab was likely triggered by a cornice chunk hitting the slope. Photo: T. Johnson

  • Cornices have grown very large and are severely overhung. They sometimes break much further back than anticipated and can take you for a nasty, sometimes fatal ride. Plus they are excellent at triggering avalanches in the wind pillows below them. This photo was taken on the ridge north of Bridger Bowl. Photo: GNFAC

  • A skier observed large cornices north of the Bridger Bowl boundary, despite the east wind several days ago eroding some snow at higher elevations. Always give these beasts a wide berth, and remember that they can break farther back than expected. Photo: H. Coppolillo

  • Cornices break easily and have killed many unsuspecting people. They fool us into thinking we are on solid ground when, in fact, we are standing on a thick diving board of snow. Give cornices a wide berth.

  • Skiers up Hyalite triggered this cornice on Mt. Bole as they traversed along the ridgeline. The cornice triggered a small slab avalanche that took out the skiers skin track. Cornices are under a lot of stress from this week's snow and wind and should be given a wide distance along ridges. Photo GNFAC 

  • Snow rangers observed this slide on a heavily wind loaded slope along a prominent ridgeline going into Tepee Basin. A good example of windward (scoured) and leeward (wind-loaded/corniced) side of ridgelines. Photo: J. Norlander

  • A skier in Hyalite observed this avalanche in the meadow below Mt. Blackmore. Strong wind over the weekend drifted snow into wind slabs at all elevations. Photo: J. Stewart

  • Cornices are extra large with all the generous snow we've had this season. These monsters and wind loaded slopes are the main avalanche concerns to start the week. On Buck Ridge today, we found 16" of new snow from the weekend's storm. We didn't see any avalanches or glaring signs of instability, and the snowpack is generally stable besides new snow and fresh wind slabs. Photo: GNFAC

  • Surface hoar 1.5-2' deep near West Yellowstone is capable of producing an avalanche, but becoming difficult to trigger. It can be easily identified as a gray stripe on a flat snowpit wall. Photo: GNFAC

  • A layer of 4-9mm Surface hoar crystals are buried 1.5-2' deep in the Lionhead area near West Yellowstone. (3mm grid) Photo: GNFAC

  • Avalanche triggered by snowmobiler on Saturday (2/10). Rider was not caught. This terrain is prone to heavy wind loading along the edges of the ridges that run down slope. Photo: J. Schmid

  • Avalanche observed Friday 2/9 around 8,800' on a southerly aspect. Likely snowmobile triggered. Photo: L. Richards

  • Eric Knoff and Doug Chabot talk about how steep a slope you need to dig a pit on to get good data. The answer is, "Not that steep".

  • Check out this blog post by Evelyn Lees at the Utah Avalanche Center on “Avalanche Fatalities During Uphill Travel.” One third of tourers die on the ascent, a surprisingly high statistic. Photo: C. Pruden

  • It feels good to be living in the snowy "Haves" vs. "Have not" group. Look at the blue squares clustered in southwest Montana. We have over 125% of average snow water content and Cooke City has over 150%! Whoop, whoop.

  • A layer of surface hoar was buried with this last storm. It is easy to find it and test; just shovel down 1-2 feet and cut a column. I could see the grains in my pit wall, but it did not break in Compression Tests or Extended Column Tests. This is good news, but it's distribution and stability is not definitively known yet. We will continue to look for it and test it. Photo: GNFAC

  • A layer of surface hoar was buried by the recent snowfall (1/19) at Lionhead. This layer was observed through most of our advisory area prior to this storm, and should be searched for by digging 1-2' deep before riding in avalanche terrain. Photo: GNFAC

  • This small slide is in the burned area of Taylor's Fork. Riders were traveling below a wind-loaded slope when they remotely triggered it. Photo: M. Gagne

  • More snow = more avalanches. Graphic is snowpack change in inches of water since 10/1/17. The storm that ended Saturday is the steep increase at the end of each line. Large avalanches were triggered during and after that storm and remain possible for a few days.

  • Natural wind slabs were observed below ridgelines in Hyalite on 1/14. Photo: K. Jamieson

  • Natural avalanche on the Fin near Cooke City. Likely ran Friday morning (1/12/18). This area had 2-3 feet of dense snow since Wednesday morning. Multiple shallower crowns are visible as well. Photo: B. Fredlund

  • This slide was triggered by skiers from flat terrain 200' away (1/12/18). They felt the ground shake and heard a "whumph". The slide was on an east aspect, about 100' wide and ran 1000'+. This is in an area with a relatively shallow and weak snowpack. This type of instability is not widespread, but possible to encounter on specific terrain, such as lower elevations or areas with a snowpack around 3-5' deep, which is relatively shallow for our advisory area right now. Photo: S. Budac

  • From an email today: "I’ve never observed so much cracking and settling as I have today. All aspects, all elevations. Even on southerly exposures with minimal snow depth. The picture shows failure on top of the Thanksgiving crust. This was in West Fork Denny Creek about 7500 feet." Photo: B. Rasmussen

  • King and Queen of the Ridge, Saturday, February 3rd. A Hike and Ski/Ride-a-Thon fundraising event to support the Friends of the Gallatin National Forest Avalanche Center. Sign up and start collecting pledges HERE.

  • Weak facets buried mid pack continue to produce unstable results in stability tests around Lionhead. With more snow and wind in the forecast, this area will likely see more avalanches. Photo: GNFAC 

  • Ace Powder Guides found the layer of facets is getting stronger compared to last week, but slowly. They were riding around Middle and Upper Teepee Creek and did three Extended Column Tests and got ECTP 13, 15, 15 which indicates instability. Photo: B. Radecky

  • Fresh pinwheels indicate the snow surface is moist and larger, wet loose slides will be possible on steep slopes. Photo: S. Magro

  • Wet loose avalanche in Hyalite that occurred during above freezing temperatures. Photo: S. Magro

  • The crown was a 2-4 feet deep hard slab and 300 feet wide. Photo: GNFAC

  • The crown is visible at the top of the slope. The rider was carried 25 feet and buried under his snowmobile, 3 feet from the surface. Photo: GNFAC

  • The slide ran 600 feet slope distance and was 36-40 degree steep. Photo: GNFAC

  • The group triggered this small slide (10' wide) on a nearby hill. They recognized it as a sign of instability and decided to not highmark or play on big slopes. They made many correct decisions, but were unlucky. Photo: GNFAC

  • Alex Marienthal stands near the 2-4 foot thick crown. The bed surface was an icy mass on the ground. Photo: GNFAC

  • Surface hoar is growing in many areas which may be a future weak layer. Photo: I. Hoyer

  • This slide was triggered with explosive by Big Sky ski patrol on 12/30. It broke on old, weak snow over the Thanksgiving crust 3-4' deep. Heavy snow and wind loading pushed deeper instabilities to a breaking point in isolated areas. Photo: BSSP

  • This slide on Buck Ridge was triggered from low angle terrain below on 12/30. Photo: P. Costanti

  • Natural avalanche at the head of McAtee basin near Buck Ridge on 12/30. Photo: T.J. Krob

  • Natural avalanche near Buck Ridge on 12/30. Crown is 4 feet deep and debris is piled in a terrain trap. Photo: T.J. Krob

  • This natural slide was observed in Tepee Basin in the southern Madison Range. Heavy snow and a weak snowpack structure are producing very dangerous avalanche conditions. Photo: B. Radecky

Weather Forecast Southern Gallatin

Extended Forecast for

17 Miles SE Big Sky MT

  • Tonight

    Tonight: Mostly cloudy, with a low around 0. Light east wind.

    Mostly Cloudy

    Low: 0 °F

  • Friday

    Friday: Isolated snow showers after 4pm.  Partly sunny, with a high near 18. Wind chill values as low as zero. Calm wind becoming west southwest 5 to 7 mph in the morning.  Chance of precipitation is 20%.

    Partly Sunny
    then Isolated
    Snow Showers

    High: 18 °F

  • Friday
    Night

    Friday Night: Scattered snow showers, mainly after 11pm.  Partly cloudy, with a low around 4. Wind chill values as low as -5. Southwest wind around 7 mph.  Chance of precipitation is 30%.

    Scattered
    Snow Showers

    Low: 4 °F

  • Saturday

    Saturday: A 50 percent chance of snow showers.  Mostly cloudy, with a high near 16. Wind chill values as low as -10. Southwest wind 7 to 11 mph.  New snow accumulation of less than one inch possible.

    Chance Snow
    Showers

    High: 16 °F

  • Saturday
    Night

    Saturday Night: Snow showers likely, mainly before 11pm.  Mostly cloudy, with a low around 5. West southwest wind 6 to 10 mph.  Chance of precipitation is 70%. New snow accumulation of around an inch possible.

    Snow Showers
    Likely

    Low: 5 °F

  • Sunday

    Sunday: A 50 percent chance of snow showers.  Patchy blowing snow after 5pm. Mostly cloudy, with a high near 19. Breezy, with a south southwest wind 8 to 16 mph, with gusts as high as 24 mph.

    Chance Snow
    Showers and
    Patchy
    Blowing Snow

    High: 19 °F

  • Sunday
    Night

    Sunday Night: Snow showers likely.  Patchy blowing snow before 8pm. Cloudy, with a low around 12. Breezy, with a south southwest wind 14 to 16 mph, with gusts as high as 24 mph.  Chance of precipitation is 60%.

    Snow Showers
    Likely and
    Patchy
    Blowing Snow

    Low: 12 °F

  • Monday

    Monday: Snow likely.  Cloudy, with a high near 22. Breezy.  Chance of precipitation is 60%.

    Snow Likely
    and Breezy

    High: 22 °F

  • Monday
    Night

    Monday Night: A 30 percent chance of snow.  Cloudy, with a low around 9.

    Chance Snow

    Low: 9 °F

The Last Word

A snowmobiler was caught and killed in an avalanche in Idaho, near the Wyoming border north of Alpine on Tuesday, February 20. This is the 3rd avalanche in SE Idaho since the beginning of the year. The East Idaho News has a preliminary report.


  <<  This is the most recent advisory.