This is Mark Staples with early season snowpack information issued Tuesday, November 5 at 7:30 a.m. Today’s information is sponsored by Grizzly Outfitters in partnership with the Friends of the Avalanche Center. This information will be updated as conditions change.
Hello winter, it’s great to see you. Snowfall totals since Saturday morning are 15 inches in the Bridger Range and areas just south of West Yellowstone. Most other places received 5-8 inches since then. This morning temperatures at ridgetops had dropped to the single digits F. On Sunday winds blew 15-30 mph generally from the W and calmed Monday to 10-15 mph.
Today temperatures will rise into the teens to 20s F and westerly winds will steadily increase through the day. Snowfall will return this evening and produce about 2 inches by tomorrow morning. Winds from the SW will get cranking on Thursday ahead of a trough of low pressure that will bring more snow Thursday night.
Wind slabs continue to be the primary concern. Several skiers near Hardscrabble Peak in the northern Bridger Range on Sunday triggered a fresh wind slab just near the ridgetop. Yesterday in that same area, I was surprised by the calm winds. Unfortunately winds will increase today and tomorrow. With plenty of cold, dry snow, winds will easily form fresh wind slabs.
A secondary but evolving problem is snow that fell in September and early October. During dry weather in late October, this snow began to facet and weaken and is now the foundation for the snowpack. Watch an explanation in this video from Cooke City. On the Sphinx near Big Sky on Saturday, Doug found weak, faceted snow capped by a fresh wind slab and retreated from his objective (video). A skier near Cooke City on Sunday experienced collapsing and cracking of the snowpack - clear evidence that these facets exist and would produce an avalanche. We have limited data on these facets. Assume they are lurking under your feet until proven otherwise.
Do two things if you get into avalanche terrain this week. ONE - look for and avoid fresh wind slabs, especially near ridgetops. TWO – look for any signs that facets near the ground could fracture and produce an avalanche. These signs include recent avalanche activity, collapsing or cracking, and unstable results in stability tests. Digging to the ground and performing a stability test can be done in just a few minutes. Otherwise, find a slope less than 30 degrees in steepness, watch for buried rocks, and enjoy the powder.
1-Hour Avalanche Awareness Classes
HELENA, November 13, 6:30 p.m. at the Basecamp.
BOZEMAN, November 19, 6:30 p.m. at REI
BIG TIMBER, November 19, 7 p.m. at Big Timber High School
BILLINGS, November 20, 6 p.m. at Basecamp
BIG SKY, November 20, 7 p.m. at Grizzly Outfitters
Go to our EDUCATION CALENDAR for details and more courses.
Intro to Avalanches w/ Field Course, MSU; 4, 5 and 7 December
Info and registration: https://www.ticketriver.com/event/7112
Snowmobiler Intro to Avalanches w/ Field Course, West Yellowstone: 19 and 20 December
Info and registration: https://www.ticketriver.com/event/7116