Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, April 5, at 7:00 AM. Today’s advisory is sponsored by Grizzly Outfitters in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
Thunder, lightning, rain and snow all blessed southwest Montana yesterday. This morning the mountains have 2-4” of new snow with temperatures in the teens to low 20s. West winds are blowing 30-40 mph and gusts hit 60 mph last night. Today will start mostly cloudy and windy with temperatures rising into the mid-40s this afternoon as dry, warm and sunny weather brings temperatures to the mid-70s by Friday. You’ll wear mud boots today, sneakers tomorrow and flippity-flops on Friday.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
The weather and the avalanche danger is whiplashing back and forth. Yesterday warmed considerably turning the snowpack to unsupportable and unconsolidated wet snow (termed isothermal). It also rained to the ridgetops which further weakened the snow. We were on the cusp of large wet avalanches, but last night’s solid freeze and snowfall saved us. We are at the mercy of the thermometer and if we get 24 hour cycles of above freezing temperatures the mountains will experience widespread wet avalanches.
A large avalanche released over the weekend on the east side of the Bridger Range in the bowl between Fairy and Frazier Lake (photo1, photo2). This was not a wet avalanche. It broke 1-3 feet deep and ran 1000 feet wide and 1,000 feet vertical. It looks similar to the avalanche last week in Sacajawea Peak and likely broke on a layer of small-grained facets. A wet avalanche on the west side of the Bridger Range in Middle Cottonwood also released this weekend (photo). Dry and wet avalanches, some large, illustrate the seriousness and complexity of avalanche danger right now. We are in a transition from winter to spring and conditions can change within hours. These are times to be extra cautious in the backcountry. Above freezing temperatures and sun will release wet loose avalanches. Shaded slopes with dry snow are also suspect given the rapidly changing weather and recent avalanche activity.
The WET SNOW avalanche danger will rise to CONSIDERABLE this afternoon as the new snow at the surface heats up and avalanches on sun-exposed slopes. Pinwheels are an obvious sign the snow is getting wet and unstable.
The DRY SNOW avalanche danger is rated MODERATE since avalanches are still possible. A moderate danger is not a green light to go for it. Weak layers are not widespread, but they are lurking on some slopes. Dig and look and recall today’s picture of the avalanche in the northern Bridger Range before dropping into exposed terrain.
Our last advisory of the season is Sunday, April 10.
I will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.
EVENTS and AVALANCHE EDUCATION
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