Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Monday, March 29th at 7:15 a.m. Today’s forecast is sponsored by Montana Chevy Dealers and Yellowstone Club Community Foundation. This forecast does not apply to operating ski areas.
Since yesterday morning wind has been southwest-west at 20-40 mph with gusts of 60-90 mph, and a gust of 104 mph at Big Sky. At 6 a.m. the mountains near Bozeman and Big Sky have 1-2” of new snow with none elsewhere, and temperatures are teens to high 30s F. This morning a strong cold front is delivering snow and temperatures 20-30 degrees F colder than yesterday. Today, temperatures will be low teens to low 20s F, wind will decrease from extreme to strong at 25-35 mph out of the west, and 3-6” of snow is possible by tomorrow morning.
Over the last 24 hours extreme southwest winds drifted 1-2 feet of recent snow into thick, unstable slabs (photo of wind transport). Today riders or skiers can trigger avalanches of wind-drifted snow 1-3 feet thick. These drifts exist along ridgelines as well as less common locations, like lower on slopes or in the trees, due to the abnormally strong wind speeds. Today’s new snow and wind will add weight and may hide visual evidence of yesterday’s drifts. Avoid steep slopes that are commonly wind loaded, like below cornices and along ridgelines. Feel for changes in snow hardness under your sled or skis, or dig and probe to feel for denser wind slabs under today’s snow.
Additionally, there is a chance avalanches can break wide on a thin weak layer under last week’s snow. We have found this weak layer to be unstable in some of our snowpits, but not all, near Cooke City (Cooke video) and Buck Ridge (video, video). Dig a quick pit to check for this layer before riding steep slopes (video).
On Saturday near Mt. Blackmore a skier remotely triggered an 8-10 foot deep avalanche that broke on weak, sugary snow near the ground (photos and details), and skiers reported a recent natural deep slab in Flanders Creek (photo). Also, a snowmobiler triggered slide near Buck Ridge broke on weak snow near the ground on a slope that previously slid on this layer (photo and details). These avalanches are the first to break on this deep weak layer since February. The likelihood is low for triggering a deep slab avalanche, but recent slides are a sign that the added weight from last week’s snow and wind-loading has made it possible to trigger a deep slab.
Upcoming Avalanche Education and Events
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:
TONIGHT!!!, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE
April 5, 6:30 p.m., Forecaster Chat with Alex Marienthal, hosted by Uphill Pursuits, “Spring Snowpack and Forecasting Tools”. Link to Join.