GNFAC Avalanche Forecast for Wed Mar 23, 2011

Not the Current Forecast

Good morning.  This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 23, at 7:30 a.m.  Yellowstone Club Community Foundation, in cooperation with the Friends of the Avalanche Center, sponsors today’s advisory.  This advisory does not apply to operating ski areas.  

Mountain Weather

Since 6 a.m. yesterday morning another 10 inches fell in the Bridger Range; 6-8 inches around Big Sky, Hyalite and Cooke City; and 1-3 inches in the southern Madison and Gallatin Ranges. Winds spiked from the southwest yesterday afternoon with gusts near 40 mph, but have calmed to 5-10 mph except Cooke City where it’s blowing 20 mph. Mountain temperatures are in the mid teens and will rise to the low thirties today under sunny skies this morning, but increasing clouds this afternoon. Today will be a good day to call in sick (sniffle, hack) to taste the powder while it lasts.

Snowpack and Avalanche Discussion

The Bridger, Madison and Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:

At times during yesterday’s storm it snowed 2-3” an hour, a ferocious pace. Storm totals are 16 inches in the Bridger Range; 10-12 inches around Hyalite, Big Sky and Cooke City; and five inches towards West Yellowstone. The snow was dense and measured 10-12% water. Ski patrols found it more difficult to trigger slides as the day progressed, but the strong afternoon winds blew lots of snow creating thicker slabs near the ridgelines. A skier touring above treeline near Cooke City said it was “hood and goggles weather”, and did not see any avalanches because of poor visibility. 

I am mainly concerned with how this new snow bonds with the old surface. I was unable to find any deep instability around Bacon Rind. Eleven days ago Eric found layers breaking 2 ½ feet off the ground, but these have strengthened. Warm temperatures the last few weeks have been the biggest influence on south facing, lower elevation slopes. At 7,700 feet I found a moist snowpack from top to bottom with no breaks in my stability tests (picture1), the first real sign that spring is here. At 9,000 feet the snowpack was mostly stable with the exception of the new snow fracturing on lower density stellar snowflakes that fell Sunday night (picture2) (snowpit). This type of weakness won’t last more than a few days.  

One to one and a half inches of snow water fell very quickly with stiff winds. The snowpack is generally strong and can handle this load, but it’s still possible to trigger avalanches in this new snow, especially on wind drifts. Sunny weather and fresh powder create an irresistible package, but don’t leave your brain behind. Today is one of those days when everything “feels right”, but make sure you back this with some decision making. Avalanches never care how you’re feeling-- they’re heartless. For today, the avalanche danger is rated MODERATE on all slopes throughout southwest Montana.

WET SNOW AVALANCHE DANGER

New snow, above freezing air temperatures and direct solar radiation will create wet snow avalanches on south facing slopes today. These will likely be point release slides, but do not under estimate the power of these to knock you off your feet and carry you into dangerous terrain.  

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.