Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, March 20, at 7:30 a.m. Grizzly Outfitters in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.
This morning temperatures were only a few degrees below freezing. Skies were clear but warmer than yesterday morning and westerly ridgetop winds were blowing 15-30 mph. Today will have more sunshine and warm temperatures which should reach the mid-40s F. Winds should blow 10-25 mph generally from the W. A ridge of high pressure currently over the area should start to leave sometime Saturday and allow an unsettled weather pattern into next week.
Bridger Range Madison Range Gallatin Range
Lionhead Area near West Yellowstone Cooke City
The snowpack is highly variable which means stability can be highly variable too. Every slope is a little different. Separate reports from Doug, Eric, and several groups of skiers show this variability.
- Near Fairy Lake in the northern Bridger Range, a group of skiers found good snow and good stability that turned to hard ice in a N facing couloir. Then, they triggered a dry snow wind slab in a seperate NE facing gully about 6-10 inches deep, 50 feet wide, and over 200 feet downhill. Watch this video of the avalanche being triggered.
- Just north of Bridger Bowl near the ridge, Doug found a frozen snowpack on an E facing slope. On a SE facing slope he found a snowpack that was wet, weak and isothermal (32 degrees F throughout). He explains more in this video.
- Further south in Hyalite Canyon, Eric found 2-4 inches of new snow on top of a frozen snowpack. He had two concerns: wet point releases involving the new snow on south facing slopes and falling cornices. See his video with a massive piece of cornice (photo) that fell naturally. On N aspects he did not find wind slabs, just good, stable skiing.
- Near Big Sky a skier reported good stability and dry snow on N aspects and horrible wet snow on S aspects by afternoon.
Dry snow on N facing slopes should be stable as long as you avoid fresh wind slabs. Frozen snow will be stable. Totally wet snow will be unstable (photo). The key to riding on south aspects is being on these slopes just as they start to warm and soften. Timing is crucial. With a light freeze overnight the transition from frozen to wet could happen quickly.
Today the avalanche danger will be CONSIDERABLE on slopes with any southerly exposure. North facing slopes will have a MODERATE danger.
I 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.