Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, April 6, at 6:45 AM. Today’s advisory is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp. This advisory does not apply to operating ski areas.
Yesterday morning a snow squall dropped 2-4” in the Bridger Range, up Hyalite and at Big Sky. In the mountains, temperatures barely cracked above freezing as west winds blew 20-30 mph with gusts of 45 mph. At 5 a.m. temperatures are in the low 20s under partly cloudy skies. Today will become mostly sunny with mountain temperatures reaching 50F before lightly freezing tonight as ridgetop winds decreasing to 15-25 mph. Today through Friday we are on track to get hit with a massive storm…a solar storm, with temperatures hitting a record breaking 70+F. My pasty white skin doesn’t stand a chance and wearing my favorite tank top is probably a bad idea, and not just because of sunburn.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Today’s avalanche danger will increase with the rising sun. Wet snow avalanches are the primary concern over the next few days. New snow that fell Monday night and Tuesday (8” in the Bridger Range and 2-4” elsewhere) will moisten and avalanche as temperatures rise above freezing. The winter snowpack is in transition. In the coming days melting snow will percolate and saturate the snowpack creating a homogenous, unsupportable Slurpee during the sunny daytime hours. Today, I expect widespread wet-loose avalanches. These are also called point-release slides because they start at one point (they look like an inverted V) and entrain wet snow as they slide downhill. They can be large and easily sweep a skier away. Slopes getting the brunt of the sun will be susceptible to sliding. Rolling and growing pinwheels of snow are a sign that wet-loose avalanches are primed to release. Sinking into wet snow past your boot tops is another. Rocky out-croppings, trees and thinner, darker, solar absorbing areas are all prime spots to trigger wet avalanches.
Timing is everything regarding wet avalanches: if it’s getting wet, stay clear. Today, the WET SNOW avalanche danger will start out as LOW and rise to CONSIDERABLE by this afternoon.
Shaded, high elevation slopes will hold onto powder for another day or two. Weak layers in the snowpack are not widespread, but a few slopes have facets buried 2-4 feet deep that can avalanche. Look no further than the large slide in the northern Bridger Range over the weekend for evidence (photo1, photo2). It broke at least 3 feet deep and 1,000 feet wide. Given these lurking instabilities, the DRY SNOW avalanche danger is rated MODERATE today.
Finally, as if there’s not enough to worry about, cornices on the ridgelines are susceptible to breaking with the warm temperatures. These truck-sized overhangs of snow will be primed to break and trigger avalanches, both wet and dry. These are dangerous and have a habit of peeling away from the ridge much further back than you may expect, taking you with them.
Our last advisory of the season is Sunday, April 10.
Alex 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.
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