Good morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 12, at 7:30 AM. Today’s advisory is sponsored by Grizzly Outfitters in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
Since yesterday morning no new snow has been recorded in the advisory area. At 5 a.m. mountain temps range from the upper 20s to upper 30s F under mostly clear skies. Winds are blowing 15-30 mph out of W-SW with stronger gusts pushing 40 mph. Today, skies will start out mostly clear, but become partly to mostly cloudy by this afternoon. Temperatures will warm into the upper 30s to mid-40s F and winds will remain moderate to strong out of the W-SW. The chance of precipitation increases through the day and the mountains will likely see a passing rain or snow shower this afternoon. These showers will be light and no real accumulation is expected. A stronger storm is forecasted to impact the area Sunday night and Monday.
WET SNOW AVALANCHE DANGER
It has been multiple days since the mountains have received a strong freeze. Although conditions will be firm this morning, above freezing temperatures combined with the potential for rain this afternoon will cause the wet snow danger to rise throughout the day. If the snow surface begins to feel soft and damp, it’s a good idea to avoid steeper slopes. Also, signs of instability such as pinwheels and point releases (wet loose avalanches) are clear indicators the surface layers are becoming unstable (photo). Avoid steeper terrain where these signs are present.
Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone Cooke City
The southern ranges including the mountains near Big Sky have picked up a healthy amount of new snow over the past few days. This new snow will create a few different avalanche problems. The primary concern today will be wet snow avalanches. While the wet snow danger will be minimal this morning, it will increase quickly with the presence of sunshine and rising temperatures. This hazard continues through the day with warming temps and the possibility of rain.
A secondary concern will be dry slab avalanches. This problem exists mainly on north facing slopes that have been wind loaded. Yesterday, the Big Sky Ski Patrol triggered wind slabs in steep, north facing terrain. There is also the possibility for skiers and riders to trigger avalanches on weak layers buried 1-3 feet deep. On some slopes a thin layer of facets sitting on an ice crust can be found 1-1.5 feet deep. On other slopes a layer of surface hoar can be found 2-3 feet deep. Since north facing slopes will hold the best riding conditions today, it will be a good idea to dig a snowpit and assess these layers before committing to steeper terrain (video).
Today, both wet and dry snow avalanches are possible and the avalanche danger is rated MODERATE.
Bridger Range Northern Gallatin Range
The primary avalanche concern in the mountains around Bozeman will be wet snow avalanches. It has now been multiple days since temperatures have dropped below freezing in the Bridger Range and in the mid to low elevations of the northern Gallatin Range. This has allowed the upper layers of the snowpack to become damp, and in some areas the snowpack has become entirely isothermal.
This morning the snowpack will be locked up due to clear skies and radiational cooling, but will soften quickly with rising temps and sun. It will be a good idea to avoid steeper terrain once the surface crust begins to break down.
Outside of the wet snow danger, it remains possible for skiers and riders to trigger isolated wind slabs on steep, wind loaded slopes. On Thursday, Alex and I observed active wind transport along the ridgeline in the northern Bridgers (video) and a group of riders reported a wind slab avalanche near Frazier Basin (photo). This problem will be confined to upper elevation slopes facing north through east.
Today, the avalanche danger will start out LOW, but will rise to MODERATE as the day progresses.
I will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.
EVENTS and AVALANCHE EDUCATION
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