Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, April 1st at 6:45 a.m. Today’s advisory is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
Over the past 24 hours, a surprise storm dropped two feet of snow in the Bridger Range and the ski area will be open for two more weeks! April Fools. Since yesterday morning, a trace to 1” of snow fell in the mountains across the advisory area. At 5 a.m. temperatures are in the 20s F under mostly clear skies. Winds are blowing 5-15 mph out of W-SW with the excepting of the mountains around West Yellowstone and Cooke City where winds are blowing out of the E-SE. Today, skies will remain mostly clear and temperatures will warm into the upper 30s to low 40s F. Winds will remain light to moderate out of the west. The current ridge of high pressure breaks down this evening increasing the chance of valley rain and mountain snow tonight and tomorrow.
Today, wet loose avalanches will be the primary concern. The snow that fell Wednesday night and Thursday morning will move easily when exposed to direct sun and warming temps. Yesterday, my partner and I took a final tour up Hyalite and found 8” of new snow above 9,000 feet. The new snow was dense and contained more than 1” of SWE (video). Alex found similar conditions in the mountains around Cooke City yesterday.
The new snow is sitting on a firm ice crust, which will make a good sliding surface. Wet loose avalanches have the potential to entrain large volumes of snow and run long distances (photo, photo). Watch for signs of instability such as roller balls and pinwheels. These are obvious clues the surface snow is losing strength and becoming unstable. Moving to shadier aspects or away from steep slopes will be a good idea if these signs are present.
A secondary avalanche problem will be wind slabs. Moderate to strong winds out of the E-NE formed wind drifts below upper elevation ridgelines. Yesterday, a skier on Mt Blackmore remotely triggered a wind slab that broke 1’ deep and 30 feet wide (photo). This slide could have caught and carried the skier into hazardous terrain. Be especially aware of this problem is you’re seeking dry snow on high north facing slopes.
Today, the wet snow avalanche danger will start out LOW, but rise to CONSIDERABLE as the day heats up. The dry snow avalanche danger is rated MODERATE on upper elevation-wind loaded slopes.
Alex will issue the next advisory tomorrow morning by 7:30 a.m. Our last advisory of the season will be Sunday, April 9th.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.
MAY 4: Give Big Gallatin Valley
The Friends of the Avalanche Center are one of the recipients of the Give Big Gallatin Valley campaign. It is a 1-day fundraising event for local non-profits on May 4, so mark your calendars. The Friends will send reminders as the day approaches: https://www.givebiggv.org/organizations/friends-of-the-gallatin-national-forest-avalanche-center