Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 23 at 7:30 a.m. Upper Yellowstone Snowmobile Club and the Antlers Lodge sponsor today’s advisory. This advisory does not apply to operating ski areas.
This morning temperatures are in the upper teens to low 20s F and winds are blowing 15-30 out of the WSW. Today, a weak storm system approaching from the north will bring an increasing chance of snow showers to the mountains around Bozeman, Big Sky and Cooke City. As the storm arrives winds will shift to the NW blowing 15-20 mph and temperatures will warm into the upper 20s to low 30s F. The mountains around Bozeman and Big Sky will likely see 1-3 inches of new snow by tomorrow morning while Cooke City will pick up 3-5 inches.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
It has now been six days since the last significant loading event. As the days tick by without new snow and wind, avalanches are becoming harder to trigger. Although the probability of triggering a slide is decreasing, it can't be entirely ruled out.
Today, there are a few avalanche problems to look out for. The first and most obvious are wind slabs. Although winds have been relatively calm over the past few days, they blew strong out of the southwest earlier in the week. These southwest winds formed isolated drifts below ridgelines and on the leeward side of cross loaded terrain features. While these old, stubborn slabs are not overly sensitive, a few may be reactive to the additional weight of a skier or rider. Watch out for and avoid wind loaded slopes.
Without the weight (stress) of new snow avalanches failing at the ground are becoming less likely. It usually takes a big storm and rapid load to reactivate these deeper layers; or, it takes finding just the right spot on the right slope to trigger a deep slab avalanche. Steep slopes with a thin snowpack are areas to look out for. Exposed rocks provide good clues for areas with thin snow (article and video on deep slabs). Given the high consequences of a deep slab avalanche, it’s best to avoid steep-rocky terrain where these monsters will be easiest to trigger.
Today, human triggered avalanches are possible on slopes steeper than 35 degrees which have a MODERATE avalanche danger. Less steep slopes have a LOW avalanche danger.
I 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.
UPPER HYALITE ROAD CLOSURE
Beginning today, the Hyalite road beyond the dam will be closed to motorized use. The Hyalite Road from the mouth of the canyon to the Blackmore Day Use site remains open. Read more in this press release.
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. Mark wrote about the deep slab avalanche problem. 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.