Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 13 at 7:30 a.m. Montana Ale Works, host of tonight’s Annual Wine Dinner (and yes, there are tickets left; 587-7700), a fundraiser for the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
Yesterday morning one inch of snow fell in the southern Madison Range, Lionhead and Cooke City areas. Temperatures warmed to near 32F at 9,000 feet and have only cooled into the mid-twenties last night. Winds have increased out of the west and are blowing 20-35 mph. Partly cloudy skies will become mostly cloudy by late this afternoon and mountain temperatures will rise into the upper thirties today. No new snow is expected; just spring-like warmth, some sun and a few muddy trailheads at lower elevations.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Yesterday I rode around Lionhead to check on the snowpack. I dug three snowpits and was pleased to find stable snow. Throughout our forecast area there are still weak layers lurking, but without a large weight of new snow they are gaining strength and not exhibiting signs of instability. We saw no avalanche activity and had no fractures on the weak (er) snow buried a few feet deep. The dry snow avalanche danger is dropping, but there are two issues to look out for: wind loading and thin snowpacks.
Wind-loading: Most of the wind-loads were formed a couple days ago. Most slabs are glued into place, but a few smooth, inviting, wind rollers could still break and avalanche (photo). The danger is that they can push you into deadly terrain traps (cliffs, trees, gulleys).
Thin snowpacks: Snowpacks less than three feet deep consist mostly of weak, sugary facets. Most slopes are 5-8 feet deep, but a few of these quickly thin out at their edges/flanks. These edges are where avalanches can be triggered from. This avalanche problem is isolated and worth remembering since it carries consequence.
Winter’s buffet of snow and wind has fattened cornices to XXXL sizes. Besides breaking easily from the mere weight of a person, they also can trigger slides as they tumble down the hill (photo). I was reminded of this as I looked up at the bus sized cornices in Lionhead yesterday.
WET SNOW AVALANCHES: Today’s temperatures will be well above freezing and create wet snow avalanches on sun exposed slopes. The slides will be wet, loose and confined to the upper few inches of the snowpack. Sinking in past your boot tops in wet snow, or seeing pinwheels gather size as they roll downhill are both early signs that the surface snow is losing strength and can avalanche.
For today, the avalanche danger is rated MODERATE on all wind-loaded slopes and on slopes that get a wet surface. All other slopes have a LOW avalanche danger. Low danger does not mean no danger. The definition of Low is “Generally safe…watch for unstable snow in isolated terrain…avalanches are unlikely…small avalanches in isolated areas”. In other words, don’t turn off your brain.
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.
Click HERE for the delicious menu to tonight’s Montana Ale Works Fundraiser Dinner
There are still tickets available to tonight’s 5th Annual Friends of the Avalanche Center Dinner and Wine Pairing at Montana Ale Works, 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.