GNFAC Avalanche Advisory for Sun Mar 31, 2013
Northern Madison Range Northern Gallatin Range Cooke City
Warming temperatures and direct sun are causing point releases on steep slopes. These signs of instability are direct clues the snowpack is becoming unstable. Photo GNFAC
4-6 inches of new snow above 9,000 ft combined with moderate northwest winds loaded upper elevation, leeward slopes. Fresh wind slab are resting over a firm ice crust on sun exposed slopes. This slide broke 4-6 inches deep, 50 feet wide and was triggered from the ridgeline. Althoug small in size, this slide could have carried a skier into unpleasant terrain. Photo GNFAC
Forecast link: GNFAC Avalanche Advisory for Sun Mar 31, 2013
GNFAC Avalanche Forecast for Sat Mar 30, 2013
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Above 8,000 ft. 1-3 inches of snow fell in most locations, below 8000 ft. precipitation fell in the form of rain. Depending on what the weather does today, there will be a few avalanche problems to consider.
GNFAC Avalanche Forecast for Fri Mar 29, 2013
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
GNFAC Avalanche Advisory for Thu Mar 28, 2013
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
This slide broke about 1 ft deep and 70 ft wide under the north face of Abiathar Peak at 9500 ft near Cooke City. It was observed on Tuesday, March 26th. Photo: B. Fredlund
Forecast link: GNFAC Avalanche Advisory for Thu Mar 28, 2013
GNFAC Avalanche Advisory for Wed Mar 27, 2013
Wet Snow Avalanche Danger
Yesterday, temperatures were not warm enough to create many wet avalanches. This will change today. Sunny skies with temperatures reaching the 40s will quickly wet the snow surface. Liquid water breaks bonds in the snowpack and weakens it quickly. Neither wind nor clouds will impede this process. Signs of increasing avalanche danger include sinking past your boot tops in moist snow and having large pinwheels roll downhill.
This avalanche occurred either Thur or Fri last week (March 21 or 22). New, wind, blown snow was the likely trigger. There was strong evidence of crossloading all season long on this slope. The crown was 3-4 feet deep and measured about 36 degrees. Photo: GNFAC
Forecast link: GNFAC Avalanche Advisory for Wed Mar 27, 2013
Today we investigated a slide on an east facing slope in the Bridger Range, just north of Ross Peak. The avalanche occurred on Thursday or Friday (March 21 or 22) after a snowstorm with wind loading. The weather stayed well below freezing until yesterday (Monday, March 25th). The sun melted the snow and water percolated down to the older and inpermeable melt-freeze crust.
Forecast link: GNFAC Avalanche Advisory for Wed Mar 27, 2013