SATURDAY, JANUARY 17

Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory 
issued on Saturday, January 17 at 7:30 a.m. This advisory does not apply to operating ski areas.

MOUNTAIN WEATHER

Clear skies, sunshine, and unseasonably warm temperatures are forecast for today. This morning 
at 4 a.m. mountain temperatures were in the mid 20s F, and winds were blowing 10-15 mph from 
the west and northwest. Today temperatures will climb to near 40 degrees F and winds will 
blow 10-15 mph mostly from the north.

SNOWPACK AND AVALANCHE DISCUSSION

The Bridger, Gallatin and Madison Ranges, and the Lionhead area near West Yellowstone:

The last significant snowfall occurred Sunday followed by a few days of light snowfall. The 
weather pattern has finally changed bringing clear sunny skies, but the structure of the snowpack 
remains the same. It contains a persistent weak layer of faceted snow crystals surrounding a 
decomposing ice crust. This weak layer exists throughout the advisory area on all aspects 
about 1-1.5 ft above the ground. Because it lies deep in the snowpack, warm weather this 
weekend will not help this layer gain strength. Additionally the avalanche hazard associated 
with a layer buried this deeply cannot be mitigated with ski cuts which are only effective with 
small soft wind slabs. While the number of avalanches will slowly decline, the destructive 
potential will remain extremely high.

On Tuesday, Karl Birkeland and I found this layer in the Bridger Range. On Thursday Ron and 
his partners found it in the northern Madison Range, and yesterday they found it in the 
southern Madison Range. Gallatin Snow Rangers near Buck Ridge saw evidence of previous 
avalanche activity on north and east facing slopes yesterday. The Big Sky Ski Patrol has 
found a similar layer in closed areas and does not trust it. In most cases this layer has 
displayed a propensity to propagate fractures and produce an avalanche. The question is: what 
will it take to initiate a fracture? Finding the wrong slope or the wrong spot on a slope is 
the answer and predicting these locations can be extremely difficult. For this reason EVERY 
slope warrants a careful assessment of stability and the consequences of being caught in an 
avalanche. I would also be aware of having a false sense of confidence inspired by sunny skies.

For today, human triggered avalanches are possible and a MODERATE avalanche danger exists on 
all slopes.

The mountains around Cooke City and the Washburn Range:

The mountains around Cooke City have a similar snowpack structure except they received over 
4 feet of snow during the last storm cycle and many slopes slid during this event. On these 
slopes, which are most of the popular ones, weak facets near the ground will continue to produce 
avalanches. Today a CONSIDERABLE avalanche danger exists on slopes steeper than 35 degrees. A 
MODERATE danger exists on all other slopes