Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, February 20th at 7:00 a.m. Today’s advisory is sponsored by Stronghold Fabrication and Gallatin Valley Snowmobile Assoc. This advisory does not apply to operating ski areas.
Mountain temperatures at 5 a.m. are -15F. In the northern mountains winds are W-NW at 15-25 mph, and 10-20 mph out of the N around West Yellowstone and SE in Cooke City. Skies will be sunny today and winds will become light and turn S-SW. Temperatures will rise into the low single digits and fall to negative single digits this evening. Clouds will increase tonight and a trace to 1” of snow may fall around West Yellowstone and Cooke City.
Cover up to avoid the cold burn of frostbite. A temperature of -15F with 20 mph wind equals a minus 42F wind chill.
Although winds have calmed around Cooke City, there was 3’ of new snow over the weekend that got blown around on all aspects and elevations. This snow measured 3” of snow water equivalent and even on slopes untouched by the wind, avalanches are still possible. Wind drifts of snow can be triggered by a skier, sledder or falling cornice. Yesterday a skier saw a 4-6’ deep avalanche on a wind-loaded slope on Mt. Republic (photo) that likely broke during the storm. It’s been 24-hours without snowfall, winds are decreasing, and the danger is dropping as the snowpack adjusts to this weekend’s load. For today, the avalanche danger is rated MODERATE on all slopes.
Yesterday, while I was warm and toasty in the office, Eric and his partner skied up Hyalite into Maid of the Mist and froze. They found the snowpack to be generally stable except on wind-loaded slopes. They ran into two others who triggered a slide when they unexpectedly broke off a large cornice mere inches from their feet as they traversed the ridge. The cornice triggered a slide on the wind-loaded slope below which erased part of their up-track (photo). This story illustrates the avalanche concern from the Bridger Range, to Big Sky and West Yellowstone. Two feet of snow since Friday was blown into drifts and fed cornices. On Sunday, Alex and I saw super-sized overhangs on Buck Ridge (photo), and snow rangers found an avalanche on a heavily wind-loaded slope in Teepee Basin (photo). Winds since Friday were all over the compass, so be wary of slopes under cornices or in gullies where drifts are most likely to be found. Alex warned us about wind-loading during Saturday’s trip to Fairy Lake (video),which mirrored Eric’s visit on Friday to Cabin Creek (video). For today, slopes that are wind-loaded have a MODERATE avalanche danger while all others have a LOW danger.
Cornices break easily and have killed many unsuspecting people, some friends of mine. They fool us into thinking we are on solid ground when, in fact, we are standing on a thick diving board of snow. Give cornices a wide berth (illustration).
If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
BOZEMAN
Feb. 28th, Know Before You Go avalanche awareness, 7:00 p.m. @ Procrastinator Theater, MSU
March 2nd and 3rd, SheJumps Companion Rescue Clinic, Info and Register HERE
March 2nd, Avalanche Awareness, 7-8:00 p.m., MAP Brewing Bozeman Split Fest
March 7th, Avalanche Awareness, 6-7:30 p.m. @ REI
DILLON
Feb. 24th and 25th, Snowmobile intro to avalanches w/ field course. More info: https://msuextension.org/conference/
COOKE CITY
Every Friday and Saturday, Current Conditions Update and Avalanche Rescue, Friday 6:30-7:30 p.m. at The Soda Butte Lodge in February. Saturday anytime between 10-2 @ Round Lake.
If you dig snowpits and record stability tests, take note, there is a change in recording shear quality and fracture character with the ECT. Read the short article, Shear Quality or Fracture Character with an Extended Column Test – No Longer in SWAG or SnowPilot.