Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued Tuesday, December 10 at 7:30 a.m. Mystery Ranch in partnership with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.
I did a double take when I looked at my thermometer in Bozeman this morning. It read 18 degrees, thirty degrees warmer than a couple days ago--almost t-shirt weather! Mountain temperatures are still chilly with minus 5-10F around West Yellowstone and Cooke City; 5-10F elsewhere. At 6 a.m. it’s snowing in the mountains with 2-4 inches falling so far. Winds picked up yesterday and are currently blowing westerly at 20-30 mph and gusting into the 40s. Snowfall will end this afternoon and winds will taper off tonight. Another 3-6 inches will fall, but I expect double that in the Bridger Range given the favorable moist, northwest flow.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
Wind-loading over the last 36 hours has changed the stability for the worse. Avalanches were reported yesterday: a small natural slide at the head of Truman Gulch in the Bridger Range, a natural slide up Hyalite in an ice filled gully appropriately named “Avalanche Gulch”, and nearby, a small wind slab was triggered by an ice climber. Strong and gusty winds coupled with new snow will create dangerous avalanche conditions throughout southwest Montana. Winds are blowing at the ridgetops and also cross-loading slopes at mid elevations. I expect more natural avalanche activity today on wind-loaded slopes.
Frigid cold temperatures are Miracle-Gro for buried facets. A week of cold temperatures has not helped the overall strength of the snowpack (snowpit, picture, video). In some areas, like the Bridger Range and around Big Sky, a weak layer of facets buried near the ground has lost even more strength. Recent wind-loads will place additional stress on this layer and avalanches may release deeper than just the new wind deposits.
Managing avalanches today is simple: stay off of wind-loaded slopes. If you see recent avalanche activity, go somewhere else. The same goes for collapsing or shooting cracks. These are simple, yet unmistakable signs of instability that should not be ignored.
Given the recent avalanche activity, new snow and strong winds, today’s avalanche danger is rated CONSIDERABLE on all slopes that are wind-loaded. Slopes not affected by the wind will have a MODERATE 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.
EVENTS/EDUCATION
BOZEMAN: Wednesday, December 11, 7 p.m., International Mountain Day, Emerson Cultural Center, Avalanche Forecasting and Awareness. http://www.mtavalanche.com/images/13/international-mountain-day
FOUR CORNERS: Wednesday, December 11, 7 p.m., 1-hour Avalanche Awareness for Snowmobilers at the GVSA Groomer Shed, http://gvsa.net/
BOZEMAN: Saturday, December 14, 10:30-11:30 a.m. Free Avalanche Transceiver Workshop, Bridger Bowl, next to the rental shop at Jim Bridger Lodge.
WEST YELLOWSTONE: Snowmobiler Intro to Avalanches w/ Field Course; 19 and 20 December. Info and registration: https://www.ticketriver.com/event/7116