Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 19 at 7:30 a.m. Beartooth Powder Guides and Northern Lights Trading Company sponsor today’s advisory. This advisory does not apply to operating ski areas.
Under clear skies mountain temperatures are near 10F with westerly winds blowing 20-30 mph. Yesterday morning another four inches fell in the Bridger and Northern Gallatin Ranges before the sun broke through. Today will start out sunny and become partly cloudy as the day progresses. Temperatures will warm into the mid-thirties with steady ridgetop winds from the west at 20-30 mph.
Northern Gallatin Range Northern Madison Range
Yesterday morning over 30” accumulated up Hyalite with 18” around Big Sky. Winds are moving this new snow near the ridgetops and this storm snow is our number one avalanche concern today. I skied up Mt. Ellis and found good bonding of the new snow to the old snow surface, but the load was so large that I did not trust the stability. A few miles away a skier on Sunday found two deep slab avalanches in Flanders drainage (photo) which was in the front of my mind as we toured. To be safe my partner and I skied the southern shoulder to lower-angled terrain instead of center punching the normal run. Last week in Beehive Basin I found weak facets at the ground barely supporting six feet of snow (snowpit profile). Although it’s likely to trigger slides in the new snow, especially if it’s windblown, the deep slab avalanche problem is very real and dangerous too. I recommend sticking to lower-angled slopes to give the snowpack time to adjust to this heavy snow load.
A large snowstorm followed by a sunny day is a dangerous combination because people have a tendency to throw caution to the wind. The snowpack doesn’t care it’s a bluebird day; it’ll avalanche just the same as a cloudy one. Keeping in mind the large load, wind-loading and deep slab avalanche problem, the avalanche danger is rated CONSIDERABLE on all slopes steeper than 35 degrees or wind-loaded and MODERATE everywhere else.
Bridger Range Southern Gallatin Range Southern Madison Range Lionhead area near West Yellowstone Cooke City
Ridgetop winds are strong enough to blow snow onto leeward slopes. These wind-loads are where the primary avalanche action is today. All our ranges have enough new snow from the storm that ended yesterday to create instability. These slopes will be easy to identify since they are found near the ridgelines with pillowy drifts. The scarier problem is that some slopes harbor weak, faceted snow at the ground which is straining under the cumulative winter load. Skiers and sledders have triggered deep slab avalanches in Cooke City from thinner, rockier spots on the slope; spots that are hidden from the surface. It reminds me of the game “Battleship” I played as a kid, or for the younger crowd, an IED on an Afghan roadway. Check out the images from Cooke City on our Photos page or watch the videos (Crown Butte1, Crown Butte2, Mount Abundance) on the recent avalanche accidents to get an idea of the deep slab avalanche problem. The slopes on Crown Butte, Daisy Pass and Mount Abundance all had tracks on them before they avalanched. Tracks do not indicate stability.
For today I recommend avoiding slopes with a wind-load. Furthermore, although the odds of triggering a deep slab avalanche are low, the consequences are high. This alone should cause you to pause and think carefully about venturing onto steep slopes. The avalanche danger today is rated CONSIDERABLE on all wind-loaded slopes steeper than 35 degrees and MODERATE elsewhere.
ACCIDENT REPORTS
10 March, Altoona Lakes Fatality (by West Central Montana Avalanche Center)
11 March, Crown Butte Fatality
15 March, Mount Abundance Injury
BLOG POSTS
Check out our latest Blog Posts. Eric wrote an article about what it takes to put out an avalanche forecast and Doug recapped some lessons from the Beehive avalanche incident in February that was published in Carve.
Mark will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.