Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 7th at 7:00 a.m. Today’s advisory is sponsored by Community Food Co-op and Excel Physical Therapy. This advisory does not apply to operating ski areas.
In the last 24 hours 4” of new snow fell outside Cooke City with 1-2” in the Gallatin and Madison Ranges and Lionhead area. Under mostly cloudy skies, temperatures are in the single digits and west winds are blowing 20-30 mph with gusts of 40-60 mph. The jet stream is overhead and will usher in wind-blown snow. By tomorrow morning the southern mountains will have 4-6” of new snow with 2-4” falling in the northern ranges.
Gallatin Range Madison Range Lionhead area near West Yellowstone Cooke City
All the mountains south of Bozeman have gotten 8-12” of snow in the last 36 hours totaling .7-1” of snow water equivalent (SWE). Wind is blowing hard out of the west and drifting this snow into thick wind slabs that will be easy to trigger. The winds are also feeding cornices at the ridgetop making the overhangs ripe for calving. On Saturday, a snowmobiler on Lionhead ridge broke a cornice that tumbled his sled 700’ downhill triggering a larger slide. The rider held onto the crown and clawed his way back up to the ridge uninjured, but not unsoiled. Yesterday there were avalanches breaking in the new snow on slopes without a wind-load. A ski tourer outside Cooke City took these photos yesterday (photo1, photo2) and the day before a skier triggered a small slide in the southern Madison Range (photo).
Strong winds and new snow mean I’ll be wary of avalanche terrain today. Triggering avalanches is likely, wind-loaded or not, and the avalanche danger is rated CONSIDERABLE on all slopes.
Bridger Range
At the moment the Bridger Range is getting the wind, but not the snowfall. The 6’ of powder that fell 9 days ago has consolidated to 1-1.5’ of snow that is still susceptible to being blown around. Increasing winds today will build slabs and cornices at the ridgelines that could be triggered, our #1 concern. Other than wind-loaded slopes the snowpack is mostly stable, but there is a caveat on lower elevation slopes on the west side of the range, namely Truman Gulch. Alex and his partner were surprised to get loud collapses (a sign of instability) as they skinned uphill (video). An ice crust with weak facets below it was breaking. He did not find this instability higher on the slope, nor did he see it the next day on the east side of the range, but we will continue looking for it, and so should you.
For today, the avalanche danger is rated MODERATE on wind-loaded slopes and LOW on all others. Even with a low danger, avalanches are possible in isolated areas (i.e. low in Truman Gulch).
I will issue the next advisory tomorrow morning by 7:30 a.m.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.
Beacon Training Park at Beall: Open and free to the public for avalanche beacon practice seven days a week from 9 a.m. to 8 p.m., southeast corner of Beall Park in Bozeman (photo).
COOKE CITY
Next weekend, March 10 and 11, UYSC 21st Annual Hog Roast. More info here. Free avalanche rescue practice on Saturday.