Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 6 at 7:30 a.m. On Site Management and 406 Brewery sponsor today’s advisory. This advisory does not apply to operating ski areas.
This morning, under partly cloudy skies, mountain temperatures are 20F with light southwest winds averaging 10-15 mph. The weather station at Lulu Pass outside Cooke City is windier with gusts reading 35 mph. Today a slow moving low pressure system will increase cloud cover and drop temperatures into the teens this evening. Winds will remain light and by tomorrow morning 1-2 inches will fall around Lionhead and Cooke City.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
The past two days of no snow and light wind are helping the snowpack strengthen and stabilize. Although weak layers can form at the surface within hours, once buried they can take weeks or even months to gain strength. Today, we have three problems to look for which are all found in the top three feet of the snowpack.
- Thin wind drifts formed this weekend, most noticeable around Cooke City. Some were triggered by skiers (photo) while others avalanched naturally (photo). Although not large, they are still capable of pushing a person into deadly terrain traps.
- Shallow snowpacks (about three feet deep or less) are weak and unsupportable. This alone is not alarming, but on some slopes it is capped by a thicker slab and can avalanche. Snowboarders triggered a small slide in the forest by History Rock on Sunday and we investigated a similar slide on Mt. Wheeler last week. A poor snowpack structure is also found on thin, rocky terrain above treeline which was responsible for the natural avalanche late last week on Hardscrabble in the Bridger Range. Photos of all three slides are here.
- Weak layers of faceted snow or buried surface hoar can be found in all ranges, but not on all slopes. These layers are only a few millimeters to a centimeter thick and might not be visible in a snowpit wall, but they can be found with a stability test (video).
Snow stability assessment is all about gathering information about the area you plan on riding or skiing. Sometimes we get advanced warning the snowpack is unstable through a collapse or whumph; bulls-eye data that slopes are dangerous. In this case digging a snowpit is unnecessary. But most times digging is the only way to ensure these layers are absent or not an issue. Given our three points of concern, triggering avalanches are still possible and the avalanche danger is rated MODERATE.
Mark 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.
Montana Ale Works Fundraiser Dinner
Tickets are on sale now to the 5th Annual Friends of the Avalanche Center Dinner and Wine Pairing on Wednesday, March 13th at 6:00 p.m. Call the host stand at 587-7700 to reserve your space. Tickets are $75 and all proceeds go to the Friends of the Avalanche Center. There are only 40 tickets available and this event sells out every year so get them while you can!