Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, March 12, at 7:30 a.m. K2 Café and Deli, in cooperation with the Friends of the Avalanche Center, sponsors today's advisory. This advisory does not apply to operating ski areas.
Yesterday's weather was sunny, windy, and relatively cool. With continued wind and a few clouds overnight temperatures didn't drop too much and were near 20 degrees F this morning. Winds were blowing 10-20 mph from the W and SW though they blew a bit stronger yesterday afternoon. Today will be noticeably warmer than yesterday, but a few clouds and gusty winds will prevent temps from feeling too hot. Winds will stay strong and gusty blowing mostly from the SW at 20-25 mph and mountain temperatures will reach the low 30s F.
The Bridger, Madison and Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
The snowpack generally contains three weak layers worth considering:
- Since December facets near the ground have made the advisories sound like a broken record but have been responsible for many avalanches and have not gone away. Fortunately, a lack of significant snowfall and mild weather has allowed this layer to lie mostly dormant. This layer alone has caused many experienced backcountry skiers and riders to dial back their ambitions this season.
- A layer of surface hoar exists about 1.5 to 2 feet deep. Skiers on Mt Ellis found this layer where it did not propagate fractures in stability tests. Nearby on Mt Wheeler I found this layer which reacted similarly; however, yesterday near Cooke City on Wolverine Peak on a north aspect, this layer propagated fractures Eric's stability tests. Without much stress from new snow this layer is not too reactive but deserves attention and a careful stability evaluation.
- A layer of either surface hoar or near surface facets formed during recent dry weather and was buried by Tuesday's feeble storm. On Mt Wheeler I was surprised at the sensitivity of this layer on north facing aspects despite being buried by only a few inches of new snow (video).
The best skiing and riding can be found on shaded northerly aspects where weak layers in the upper 2 feet of the snowpack are generally the weakest. Fortunately these layers are not buried deeply and stability assessments can be done quickly and easily. Also watch for recently formed wind slabs on N and NE aspects. Eric found these fresh wind slabs near Cooke City and patrollers at Bridger Bowl and Big Sky have found them about 6-8 inches thick. With wind and a few clouds, southerly aspects shouldn't heat up enough to cause much wet snow problems, but this could change if skies clear and winds calm. Today human triggered avalanches are possible and the avalanche danger is rated MODERATE.
New Beacon Park: Skiing or riding near West Yellowstone? Consider testing your beacon skills at a new beacon park near the old airport where you can search for one or multiple beacons pre-placed in the snow and switched on/off by a control panel. Look for it by orange snow fence and signage just south of the snow cross track. For more information on beacon parks, visit: http://bit.ly/dqXrFM
I will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry let us know what you find. You can reach us at 587-6984 or email us at mtavalanche@gmail.com.