Good Morning and Happy St. Patrick's Day. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Monday, March 17 at 7:30 a.m. Lone Peak Brewery and World Boards sponsor today’s advisory. This advisory does not apply to operating ski areas.
There may not be a pot of gold in the clouds, but there is a silver lining. That lining is made out of snow which will be falling for much of the day. The storm hasn't done much yet, but with a little luck, the northern mountains and Cooke City area should see 4-6 inches by day's end. The mountains around West Yellowstone will pick up 3-5 inches.
This morning temperatures are in the upper 20s to mid-30s F and winds are blowing 15-25 mph out of the WSW with stronger gusts reaching into the 30s. Today, temperatures will start out warm, but will drop rapidly as the approaching cold front moves over the area. Valley rain and mountain snow will begin by 8-9 a.m., but precipitation will change to all snow by noon. Temperatures will likely drop 10-15 degrees as cold air behind the front settles in. Winds will gradually shift to the NW by this afternoon blowing 15-25 mph. Snow will taper off by midnight and Tuesday looks to be a drier day.
Cooke City
Today is not the day to be chasing leprechauns around the mountains of Cooke City. The fresh powder may be as tempting as pots of gold, but don't be fooled - there is still plenty of potential for large and destructive avalanches in the backcountry.
Over the past week, riders have been unlucky and have paid the price. Last Wednesday, a snowmobiler was killed in an avalanche on the northeast face of Crown Butte (accident report). On Saturday, a snowmobiler suffered two broken legs when they were caught in a slide on the south face of Mt. Abundance (photo, photo). Another snowmobiler had a very close call on Saturday below Chimney Rock near Daisy Pass and had to deploy their airbag (photo).
The scariest part about this situation is avalanches are releasing on facets near the ground - think about the entire winter's snowpack roaring down the mountain. Yesterday, Mark and Doug investigated the accident site on Mt. Abundance (video). While riding in the area they observed multiple riders climbing steep slopes – this is a not a good idea.
The best way to deal with these conditions is avoidance - stay off steep slopes and out from avalanche runout zones. Tracks on a slope do not mean it is stable.
As snow and wind impact the area today, fresh wind slabs will become a growing problem. Pay close attention to changing conditions and don’t be afraid to alter plans if instability is on the rise.
Today, dangerous avalanche conditions exist on slopes steeper than 35 degrees which have a CONSIDERABLE avalanche danger. Less steep slopes have a MODERATE avalanche danger.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone
Warm and sunny weather over the past 48 hours has created a thick crust on sun-affected slopes. North facing slopes still hold sheltered powder. Today's storm will make new snow instabilities the primary avalanche problem. Bonding issues between the existing snow surface and the new snow will be something to keep an eye out for. Strong westerly winds will likely form sensitive wind drifts as new snow becomes available for transport.
A more complex problem is triggering avalanches that break on deeper layers in the snowpack. Facets buried mid-pack and near the ground still hold the potential to propagate fractures and produce large avalanches (photo, photo). These types of avalanches will be easiest to trigger in steep, rocky terrain where the snowpack is thinner.
Today, human triggered avalanches are possible and the avalanche danger is rated MODERATE. The avalanche danger could rise to CONSIDERABLE on steep and wind loaded slopes if today’s storm hits harder than expected.
CORNICES
Cornices are large now and creep during warm weather. They are unpredictable, deadly, and often break further back than you would expect. Give these monsters a wide berth.
Doug 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.